metallogeny of the handagai skarn fe cu deposit northern great xing an range ne china constraints on fluid inclusions and skarn genesis abstract the newly discovered handagai skarn fe cu deposit is located in the northern great xing an range of ne china and is hosted by the ordovician luohe formation the orebodies that form the deposit are generally concordant with the bedding within these sediments and are spatially related to areas of skarn development the fe cu mineralization in this area records four stages of paragenesis namely prograde skarn retrograde skarn quartz sulfide and quartz carbonate stages the handagai deposit is a calcic skarn that is dominated by an andradite diopside epidote actinolite assemblage the mineralogy and geochemistry of the skarn indicate that it formed from a hydrothermal fluid that altered the carbonate units in this area to a garnet and42 95grs4 53 and pyroxene di71 78hd22 29jo0 2 bearing skarn the epidote within the skarn has an epidote end member composition with the chlorite in the skarn dominantly fe rich indicating that these minerals formed in an fe rich environment the petrographic microthermometric and raman spectroscopic analysis of fluid inclusions within garnet epidote actinolite quartz and calcite precipitated at different stages of formation of the handagai deposit indicate that mineralization related fluid inclusions are either liquid rich two phase h2o nacl type i gas rich two phase h2o nacl type ii three phase liquid vapor solid h2o nacl type iii or co2 h2o nacl inclusions type iv the early stages of mineralization are associated with all four types of inclusion whereas the later stages of mineralization are only associated with type i and ii inclusions inclusion homogenization temperatures vary between the four stages of mineralization 370 c 530 c and 600 c 210 c 290 c 190 c 270 c and 150 c 230 c from early to late respectively with salinities also varying between the earlier and later stages of mineralization 11 18 and 45 7 15 6 9 and 3 7 wt nacl equivalent equiv respectively the majority of the inclusions within the handagai deposit have homogenization temperatures and salinities of 200 c 350 c and 4 14 wt nacl equiv respectively indicating that this is a medium high temperature and medium low salinity type deposit the fluid inclusions were trapped at pressures of 11 to 72 mpa corresponding to depths of 0 4 to 2 9 km the geology mineralogy geochemistry and fluid inclusions microthermometry indicate that the handagai deposit formed as a result of contact infiltration metasomatism with the deposition of ore minerals resulting from a combination of factors that include boiling as a result of reduced pressure cooling and fluid mixing

clay minerals in late glacial and holocene sediments of the northern and southern aegean sea different source areas oceanography and climate regimes influenced the clay mineral assemblages and grain size distribution of two sediment cores from the north and south aegean sea during the last glacial and the holocene in the north aegean sea clay mineral composition is mainly controlled by sea level evolution melting of southeastern european glaciers and establishment of the connection between the black sea and aegean sea the long term development of clay mineral assemblages in the south aegean sea reflects changes in the nile discharge and african dust input at this site the establishment of pluvial conditions in the nile catchment during the early to middle holocene resulted in a substantial rise in smectite illite ratios in the late holocene stepwise aridification of the southern borderlands caused an increase in windblown sediment material and a decrease in nile suspended material the clay mineral records exhibit periodic millennial scale fluctuations in the north aegean sea the changes are centred at a period of 1 3 1 8 ka and can be attributed to short term climate and weathering changes in the northern borderlands the changes in the south aegean sea are centred at periods of 3 2 4 3 1 9 2 4 and 1 3 1 7 ka reflecting short term changes in wind strength and northeast african hydrology 2007 elsevier b v all rights reserved

evidence of saharan dust in upper pleistocene reworked palaeosols of north west sardinia italy palaeoenvironmental implications abstract a multi disciplinary approach was followed to investigate two thick palaeosolstrata that alternate with wind blown dominated deposits developed along thealghero coast north west sardinia italy optically stimulated luminescenceages reveal that both palaeosols were developed during cooler drier periods the rst one at around 70 ka marine isotope stage 4 and the latter around 50 ka marine isotope stage 3 in contrast the pedological features indicate that thepalaeosols underwent heavy weathering processes under warm humid to sub humid conditions characteristic of the sardinian climate during the lastinterglacial stage marine isotope stage 5e to reconcile this apparent datadiscrepancy a range of sedimentological and pedological analyses wereconducted these analyses reveal that the palaeosols possess a complexhistory with accumulation and weathering occurring during marine isotopestage 5e and erosion colluviation and nal deposition taking place during thefollowing cold stages thus even if these reddish palaeosols were last formedduring the glacial period the sediments building up these strata probablyrecord the climate of the last interglacial stage marine isotope stage 5e traceelement and x ray diffraction analyses together with scanning electronmicroscope images reveal the presence of saharan dust in the parentmaterial of the palaeosols however no evidence of any far travelled africandust has been observed in the marine isotope stage 4 3 aeolian deposits it ispossible to conclude that in the west mediterranean islands saharan dustinput even if of modest magnitude is preserved preferentially in soilsaccumulated and weathered during interglacial stages keywords marine isotopic stage mediterranean osl dating trace elementgeochemistry xrd analysis sedimentology 2012 59 917 938

aeolian dust in europe african sources and european deposits abstract a conceptual model is presented for the provenance and dispersal patterns of small dust that falls on europe generally its sources are in north africa and it is distributed across all europe several key sources can be distinguished sahelian dust comes largely from the old lake chad region this is a clay rich unimodal material saharan dust comes from the great sand sheets it contains small monomineralic particles and may have a bimodal size range three simple deposition zones can be recognised a d1a zone where sufficient dust is deposited to form a discrete soil layer not well classified as a rendoll in the extreme south of europe a d1b zone where the airborne dust simply provided a silty admixture to soil systems across middle europe and a northern zone d1c where the dust is a fugitive cloud but very occasionally forms noticeable deposits two particle formation methods can be noted particle control in sahelian dust is via the sedimentation in the original lake this gives an open structure which can be modelled using a simple monte carlo approach the open structure ensures that only small particles are produced size control is via particle packing a chipping mechanism can produce fine quartz particles from sandy deserts the aeolian energy is by and large not sufficient to cause major impact fracturing but small mineral chips can be produced in the small dust size fine and very fine silt which go into high level suspension and travel to europe and beyond the saharan material can have a wider more variable size distribution than the sahelian material the canary islands loess is largely sahelian material the cape verde islands deposits from the nearby sandy regions are saharan deposits large dust has fallen on europe and produced widespread loess deposits large dust is essentially an in continent deposit small dust comes from outside from africa

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

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

in situ la mc icp ms and id tims u pb geochronology of cassiterite in the giant furong tin deposit hunan province south china new constraints on the timing of tin polymetallic mineralization abstract the furong deposit located in southern hunan province china is a newly discovered giant tin deposit spatially associated with the a type qitianling granite the petrogenetic link between the giant furong tin deposit and the qitianling granite batholith remains controversial because of the lack of precise dating for the tin polymetallic mineralization here we report for the first time in situ u pb data on cassiterite obtained by la mc icp ms and the results are compared to id tims data the in situ la mc icp ms analyses of the cassiterites provide a reliable age constraint for tin polymetallic mineralization in the furong deposit yielding an isochron age of 159 9 1 9 ma at 95 confidence level mswd 18 which is indistinguishable from the id tims 206 pb 238 u weighted mean age of 158 2 0 4 ma the in situ u pb ages corroborate the ar ar dates published for the furong tin deposit which indicate that the mineralization is coeval with the emplacement of the qitianling granite batholith these results provide further evidence of a close temporal link between the pluton s emplacement and tin mineralization in the furong area the data obtained clearly demonstrate that in situ la mc icp ms u pb dating of cassiterite is a robust geochronometer for direct dating of tin polymetallic mineralization

end permian to mid triassic termination of the accretionary processes of the southern altaids implications for the geodynamic evolution phanerozoic continental growth and metallogeny of central asia the altaids is one of the largest accretionary orogenic collages in the world with the highest rate of phanerozoic continental growth and significant metallogenic importance it is widely accepted that subduction related orogenesis of the altaids started in the late precambrian and gradually migrated southward present coordinates however it is uncertain when and how the building of the altaids was finally completed based on structural geology geochemical geochronological and paleomagnetic data this paper presents late paleozoic to early mesozoic accretionary tectonics of two key areas north xinjiang in the west and inner mongolia in the east together with neighboring mongolia the late paleozoic tectonics of north xinjiang and adjacent areas were characterized by continuous southward accretion along the wide southern active margin of siberia and its final amalgamation with the passive margin of tarim which may have lasted to the end permian to early mid triassic in contrast in inner mongolia and adjacent areas two wide accretionary wedges developed along the southern active margin of siberia and the northern active margin of the north china craton which may have lasted to the mid triassic the final products of the long lived accretionary processes in the southern altaids include late paleozoic to permian arcs late paleozoic to mid triassic accretionary wedges composed of radiolarian cherts pillow lavas and ophiolitic fragments and high pressure ultrahigh pressure metamorphic rocks permian alaskan type zoned mafic ultramafic complexes intruded along some major faults of the tien shan we define a new tarim suture zone immediately north of the tarim craton that is probably now buried below the tien shan as a result of northward subduction of the tarim block in the cenozoic the docking of the tarim and north china cratons against the southern active margin of siberia in the end permian to mid triassic resulted in the final closure of the paleoasian ocean and terminated the accretionary orogenesis of the southern altaids in this part of central asia this complex geodynamic evolution led to formation of giant metal deposits in central asia and to substantial continental growth

suspended particulate matter and nepheloid layers over the southern margin of the cretan sea n e mediterranean seasonal distribution and dynamics seawater along the southern margin of the cretan sea may 1994 september 1995 has been found to have light transmission values ranging from 79 to 94 corresponding to spm values ranging from 1 5 mg l 1 to 0 2 mg l 1 the highest spm concentrations mostly of terrigenous origin were found close to the sea bed over the shelf break and upper slope the origins of spm in the surface waters 150 m is principally biogenic the occurrence of nepheloid layers at intermediate depths within the upper water column is mostly a result of density stratification the dynamics of spm distributions are governed by the 2 gyre system which induces a general onslope flow and so inhibits the seaward dispersion of the relatively more turbid coastal shelf waters this is in agreement with the virtual absence of suspensates of terrigenous origin offshore of the shelf break near bottom nepheloid layers bnl and detached intermediate nepheloid layers occur in the vicinity of the shelf break and over upper slope region these may be explained by resuspension induced by near bed current activity and breaking of internal waves high concentrations of spm near the seabed may be caused by anthropogenic trawling activity occasionally the formation of bnl may result from local seismic activity resulting in gravity driven mass movements

the remarkable re os chronometer in molybdenite how and why it works the re os rhenium osmium chronometer applied to molybdenite mos2 is now demonstrated to be remarkably robust surviving intense deformation and high grade thermal metamorphism successful dating of molybdenite is dependent on proper preparation of the mineral separate and analysis of a critical quantity of molybdenite unique to each sample such that recognized spatial decoupling of 187re parent and 187os daughter within individual molybdenite crystals is overcome highly precise accurate and reproducible age results are derived through isotope dilution and negative thermal ion mass spectrometry id ntims spatial decoupling of parent daughter precludes use of the laser ablation icp ms microanalytical technique for re os dating of molybdenite the use of a reference or control sample is necessary to establish laboratory credibility and for interlaboratory comparisons the rb sr k ar and 40ar 39ar chronometers are susceptible to chemical and thermal disturbance particularly in terranes that have experienced subsequent episodes of hydrothermal magmatic activity and therefore should not be used as a basis for establishing accuracy in re os dating of molybdenite as has been done in the past re os ages for molybdenite are almost always in agreement with observed geological relationships and when available with zircon and titanite u pb ages for terranes experiencing multiple episodes of metamorphism and deformation molybdenite is not complicated by overgrowths as is common for some minerals used in u pb dating e g zircon monazite xenotime nor are re and os mobilized beyond the margins of individual crystals during solid state recrystallization moreover inheritance of older molybdenite cores incorporation of common os and radiogenic os loss are exceedingly rare whereas inheritance common pb and pb loss are common complications in u pb dating techniques therefore molybdenite ages may serve as point in time markers for age comparisons

la icp ms zircon u pb and molybdenite re os isotope ages and metallogenic geodynamic setting of banlashan mo deposit inner mongolia located in the southern part of the da hinggan mountains the newly discovered banlashan mo deposit in ar horqin banner of inner mongolia is a medium size explosive breccia type mo deposit the rhyolite host rocks and post ore granite porphyry dikes yield la icp ms zircon u pb ages of 157 5 3 3 ma and 126 3 2 1 ma respectively five re os isotopic analyses of molybdenite separates yield an isochron age of 136 1 6 6 ma mswd 0 42 these ages show that both the rhyolite rocks and the granite porphyry dikes have no genetic relation with the mo mineralization which has been proved by field investigation and that the mineralization related intrusion that resulted in hydraulic brecciation of the rhyolite was possibly seated in the depth these new data together with the published isotope ages for the mineralizations and their related intrusions in southern da hinggan mountains suggest that the majority of the intrusion related mineral systems comprising porphyry skarn and veins were formed in the period of 150 130 ma i e the transition from late jurassic to early cretaceous this major metallogenic event occurred in a back arc extensional regime related to pacific plate subduction following paleozoic subduction related accretion and triassic jurassic collision related crustal thickening of the central asian orogenic belt the definition of the banlashan explosive breccia type molybdenum deposit indicates that a porphyry type mo mineralization possibly exists below the breccia type mo mineral ization which is of significance for future exploration in the banlashan mo deposit

reconstructing saharan dust transport to the eastern mediterranean sea during the last 180 ka using endmember modelling of grain size data endmember modelling on the terrigenous silt fraction of nine marine sediment cores spanning up to 180 000 years reveals the influx of north african dust into the eastern mediterranean sea the dust grain size modes decrease with transport distance from 50 m off the african coast to ca 30 m in the aegean sea the dust signal is strongly influenced by hydrological changes in northern africa changes from arid to humid periods are documented in the grain size data of all cores the climatic signal gets weaker with growing distance from the source and close to large fluvial sediment sources such as the nile frequency and wavelet analyses show a strong orbital precession signal that is known to trigger the migration of the monsoonal rain belt in northern africa the influence of climate changes on suborbital time scales on dust influx is less distinct but dansgaard oeschger interstadials and heinrich like events are documented in some cores in the sediment core closest to the source three endmembers represent one or more dust sources in northern africa with growing distance from the source the three modes cannot be separated anymore and appear as one multimodal dust endmember

characterization and origin of aluminous a type granites from the lachlan fold belt southeastern australia the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are a distinctive group of igneous rocks on the basis of chemical and mineralogical criteria those granites that contain 65 72 sio2 can be distinguished from other types on the basis of higher abundances of fetotal fetotal mg high field strength elements trivalent rare earth elements ga and zn mineralogically they contain fe rich hydrous mafic minerals and primary ilmenite and hence are reduced relative to the ni nio buffer however the extremely felsic a type granites sio2 72 have the same chemical and mineralogical characteristics as felsic fractionated i type granites recent analyses indicate that the lachlan fold belt a type granites have sc f alkali element trace transition element and h2o contents similar to those of other unfractionated i type granites rb sr and nd sm isotopic compositions are highly variable probably reflecting source region heterogeneity the metaluminous to weakly peraluminous a type granites of the lachlan fold belt are distinct from peralkaline rocks in terms of chemical composition petrography and field associations although these rocks have been grouped together as a single type in current classification schemes we propose that the metaluminous to weakly peraluminous a type granites such as those of the lachlan fold belt should be defined as aluminous a type granites and should not be grouped with peralkaline granites the lachlan fold belt aluminous a type granites have relatively high calculated zircon saturation temperatures we suggest that these granites were produced by high temperature partial melting of a felsic infracrustal source

nd isotopic variation of paleozoic mesozoic granitoids from the da hinggan mountains and adjacent areas ne asia implications for the architecture and growth of continental crust abstract there is a long standing controversy regarding the tectonic division composition and structure of the continental crust in the da hinggan mountains and adjacent areas which are mainly part of the southeastern central asian orogenic belt caob this paper approaches these issues via neodymium isotopic mapping of paleozoic mesozoic 480 to 100 ma granitoids on the basis of 943 published and 8 new whole rock nd isotopic data the study area can be divided into four nd isotopic provinces i ii iii and iv province i the youngest crust nd model ages tdm 0 8 0 2 ga is a remarkable region of phanerozoic crustal growth which may reflect a major zone for closures of the paleo asian ocean province ii slightly juvenile crust tdm 1 0 0 8 ga the largest nd isotopic province in the southeastern caob is considered to reflect the recycling of the initial crustal material produced during the early stage early neoproterozoic evolution of the paleo asian ocean province iii slightly old crust tdm 1 6 1 1 ga is characterized by ancient crustal blocks such as the central mongolian erguna dariganga and hutag uul xilinhot blocks which represent micro continents and precambrian basements in the southeastern caob several parts of province iii are located along the northern margin of the north china craton ncc which is interpreted as a destroyed cratonic margin during the paleozoic and mesozoic province iv the oldest crust tdm 2 9 1 6 ga mainly occurs within the ncc and reflects its typical precambrian nature these mapping results indicate that the boundary between provinces ii and iii the northern margin of the ncc along the solonker xar moron fault can be regarded as the lithospheric boundary between the caob and ncc provinces i and ii account for 20 and 44 of the area of the southeastern caob respectively and therefore the ratio of continental growth is 64 from the neoproterozoic to the mesozoic which is typical for this part of the caob and distinguishes the caob from other phanerozoic orogens in the world

himalayan cu mo au mineralization in the eastern indo asian collision zone constraints from re os dating of molybdenite we present new re os molybdenite age data on three porphyry cu mo au deposits yulong machangqing and xifanping these deposits are associated with the himalayan adakitic magmatism that occurred in a continental collision environment controlled by large scale cenozoic strike slip faults in the eastern indo asian collision zone three distinct episodes of cu mo au mineralization are recognized at yulong re os isotopic data of four molybdenite samples from sulfide quartz veins in the quartz sericite alteration zone yield an isochron with an age of 40 1 1 8 ma 2 coincident to a zircon sensitive high mass resolution ion microprobe shrimp age of 40 9 0 1 ma for the host monzogranite the molybdenite re os dates together with k ar rb sr u pb and 40ar 39ar dates on the pre and intra ore porphyries suggest that cu mo au mineralization formed during the late stage 40 ma of regional porphyry magmatism but hydrothermal activity probably lasted to at least 36 ma at machangqing molybdenite re os data from the k silicate and quartz sericite alteration zones yield an isochron with an age of 35 8 1 6 ma 2 which is identical to the zircon shrimp and bulk rock rb sr ages 35 36 ma of the host granite but older than bulk rock k ar dates 31 32 ma for associated au bearing quartz syenite with advanced argillic alteration at xifanping five molybdenite samples from the k silicate alteration zone yield the youngest re os isochron age in the area at 32 1 1 6 ma 2 the re os molybdenite dates here are younger than k ar ages 33 5 34 6 for hydrothermal biotite and actinolite there is a positive correlation between the absolute age of the deposits and their cu and au reserves in the eastern indo asian collisional zone episodic stress relaxation probably caused multiple magmatic intrusions which most likely resulted in three episodes of cu mo au mineralization in the eastern indo asian collision zone

metallogenic regularity and minerogenetic series of ore deposits in inner mongolia and adjacent areas in the discipline of ore deposits minerogenetic series is a kind of academic thought of studying regional metallogeny it advocates using system theory and activity theory to study ore forming process and ore deposit association that have been developed in various stages of geological history and in specific tectonic environment in this study based on the new understanding of tectonic evolution of inner mongolia the new progresses in geosciences of its adjacent areas especially a large number of precise mineralization ages data and the new understanding of the sources of rock forming and ore forming materials the authors divided the ore deposits in inner mongolia into 11 metallogenic series the archaean anshan type metamorphic sedimentary iron deposit metallogenic series consisting of the middle archaean and the late archaean series the middle proterozoic submarine exhalative type lead zinc copper sulfur deposit metallogenic series the mesoproterozoic bayan obo ree fe nb deposit metallogenic series the ordovician silurian porphyry copper deposit metallogenic series the devonian ophiolite related chromite deposit metallogenic series the late permian triassic granite related molybdenum gold polymetallic deposit metallogenic series the triassic middle jurassic porphyry copper deposit metallogenic series the late jurassic early cretaceous granite related epithermal type lead zinc polymetallic deposit metallogenic series in de erbugan area the late jurassic early cretaceous granite related lead zinc tin molybdenum gold polymetallic deposit metallogenic series in the da hinggan mountains and adjacent areas the cenozoic lacustrine sedimentary evaporation related salt deposit metallogenic series furthermore on the basis of such division the ore deposit metallogenic series distribution map was drawn up with a brief discussion on their ore forming geological background mineralization characteristics ore deposits association and spatia l temporal distribution patterns the metallogenic series division in this study emphasizes the importance of tectonic events and highlights the coupling between the major tectonic events and the large scale m i neralization with the purpose of recognizing the geological background of the mineralization episode on a larger scale for example the authors set the two coeval deposits of duobaoshan and bainaimiao as a metallogenic series though it is not clear whether they belonged to the same intermittent arc chain or whether they were split by later tectonic movement it is worth noting that a lot of minerogenetic series in inner mongolia show signif i cant diachronism for example the metallogenic events related to the closure of paleo pacifc ocean lasted from late carboniferous through permian to triassic and those related to the subduction of mongo l okhotsk ocean lasted from triassic to middle jurassic

regressive and transgressive sequences in a raised holocene gravelly beach southwestern crete both a modern and a raised late holocene gravelly beach have been studied along the cliffed coast near the village of chora sfakion in southwestern crete greece the holocene beach shows the record of regional well documented relative sea level changes in the form of regressive and transgressive sequences the texture fabric and depositional architecture of these sequences are described and compared with those of the modern microtidal beach there the depositional history of the raised beach is discussed in terms of the sediment transport processes and relative sea level changes the regressive sequences of both the modern and the holocene beach resemble those of the mesotidal beaches in the sker district of southwest wales described by bluck 1967 the transgressive sequence of the holocene beach resembles the mesotidal beach sequence near newton southwest wales recognized by bluck as another type of progradational regressive beach therefore transgressive beach sequences in the stratigraphic record might easily be overlooked or misinterpreted as regressive the stratigraphic depositional patterns of gravelly beach systems are apparently still poorly understood

geochronology and isotopic geochemistry of the a type granites from the huanggang sn fe deposit southern great hinggan range ne china implication for their origin and tectonic setting abstract the huanggang sn fe deposit inner mongolia is located in southern great hinggan range metallogenic belt la icp ms zircon u pb dating show that the k feldspar granite and granite porphyry in the huanggang mine were formed at 136 7 1 1 ma and 136 8 0 57 ma respectively sr nd pb isotope of the rocks and in situ zircon hf isotopic systematics show that 87 sr 86 sr i values range from 0 70211 to 0 70729 close to the 87 sr 86 sr i of oceanic basalts and lower than those of continental crust the e nd t values and nd model ages t dm vary from 0 8 to 0 9 and 855 to 993 ma respectively the pb isotopic compositions are also variable with 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of 18 974 26 107 15 554 15 914 and 38 894 39 890 respectively suggesting that the lead is derived from a mixed source the 176 hf 177 hf values range from 0 282744 to 0 282922 with corresponding e hf t values ranging from 1 9 to 18 3 and two stage hf model ages t dm2 of between 561 and 888 ma the isotope composition shows that huanggang granites were derived from partial melting of juvenile lower crust that originated from depleted mantle perhaps contaminated by small amounts of ancient continental crust younger nd hf isotope model ages imply that an important crustal growth event took place in this area during the neoproterozoic integrating our data with previously published results and the late mesozoic regional tectonic setting we conclude that the huanggang granites were generated in an intraplate tectonic magmatic setting asthenospheric mantle upwelling due to lithospheric delamination and magma underplating caused the partial melting of a mantle wedge metasomatized by the fluids released from subducted oceanic crust or by decompression of depleted mantle this resulted in remelting differentiation and a continued evolution of the mafic juvenile crust producing a large quantity of granitic magma the tectonic setting for these processes may be linked to the nnw subduction of the pacific plate izanagi in the mesozoic which affected most of eastern china

the provenance of sediments in the gulf of lions western mediterranean sea in this study we undertook a reconnaissance study of sediments provenance in the gulf of lions focusing over the last 16 ka we used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing sediments samples were selected both onshore and offshore from the western eastern and central part of the gulf of lions we analyzed bulk sediments coarse and fine silt and clay fractions elemental and nd isotope compositions appeared to differ from one grain size fraction to another one these are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the nd isotope compositions our results indicate that sediments in the gulf of lions mainly originated from the rhone river watershed although a contribution of saharan dust is seen in one sample influence of pyrenean small rivers is minor in these samples some sr isotope compositions shifts are interpreted as reflecting variable amounts of chemical weathering that are consistent with published paleoclimatic reconstructions

constraints on the timing of uplift of the yanshan fold and thrust belt north china this paper reports in situ u pb ages and hf isotopic data on detrital zircons from paleozoic to late mesozoic strata in the xishan area near beijing that provide important constraints on the evolution and paleogeography of the northern part of the north china craton ncc zircons from carboniferous to late mesozoic sandstones are characterized by three major groups of u pb ages 2 5 2 3 ga 1 9 1 7 ga and late phanerozoic ages the neoarchean and paleoproterozoic zircons and some phanerozoic zircons have negative ehf t values similar to igneous zircons from intrusive rocks known from the ncc indicating that the source of the sandstones was locally derived however late triassic to late jurassic 205 158 ma sandstones contain a group of phanerozoic zircons with positive ehf t values distinct from known igneous zircons in the ncc suggesting an exotic source the nearest potential source is the xing meng orogenic belt xmob to the north of the ncc where considerable amounts of juvenile crustal materials exist it is concluded that there are two sudden shifts in source provenances of the xishan sediments from the ncc before the late triassic to a mixed source from the ncc and xmob during the late triassic to late jurassic and then from the ncc again during the late jurassic 158 ma the first shift in source resulted from the exhumation and denudation of rocks due to uplift of the xmob which coincided with post collisional extension in the late triassic and intraplate extension of the ncc in the middle to late jurassic the second source shift resulted from the uplift of the yanshan fold and thrust belt thus constraining the timing of this to the late jurassic

high sr y magmas reflect arc maturity high magmatic water content and porphyry cu mo au potential examples from the tethyan arcs of central and eastern iran and western pakistan the temporal and geochemical evolution of arc magmatism that culminated in porphyry cu mo au deposit formation has been studied in three separate neo tethyan arc systems in central and eastern iran and western pakistan porphyry cu au deposits in the lut block of eastern iran formed in the middle eocene at the end of a period of extensive paleocene eocene volcanism porphyry cu mo deposits in the kerman belt of central iran formed in the middle miocene at the end of a period of voluminous eocene oligocene volcanism and porphyry cu au deposits in the chagai belt of western pakistan formed in four pulses during the eocene early miocene middle late miocene and late miocene pliocene after a prolonged period of arc magmatism that began in the late cretaceous and is still active in each region the late porphyry related magmas are more geochemically evolved and more hydrous as evidenced by the presence of hornblende phenocrysts than the preceding volcanic rocks we suggest that this reflects maturation of the arc magmatic system over a period of tens of millions of years leading to the generation of more evolved volatile rich magmas at later stages of the arc s history high magmatic water contents are a prerequisite for the shallow crustal emplacement of arc magmas and the subsequent generation of potentially ore forming subvolcanic magmatic hydrothermal systems it is thus suggested that the fertility of arc magmas within a given arc terrane can be assessed by observing the relative timing of plutonic suites later suites are more prospective noting the common presence of hornblende or biotite phenocrysts indicating high magmatic water contents and through lithogeochemical fingerprinting of magmatic fractionation processes relatively high sr y and la yb ratios and eun eu ratios 1 indicating abundant early hornblende fractionation and suppression of plagioclase crystallization in hydrous magmas

mesozoic metallogeny in east china and corresponding geodynamic settings an introduction to the special issue abstract the giant east china mesozoic metallogenic province hosts some of the world s largest resources of tungsten tin molybdenum antimony and bismuth ores of gold silver mercury lead zinc copper uranium and iron are also of major importance the province and its constituent metallogenic belts or regions south china middle lower yangtze river valley east qinling dabie interior of north china craton yan liao and north east china are the products of several pulses of igneous activity and mineralisation between 240 and 80 ma each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the mesozoic this geodynamic evolution is linked to a complex series of tectonic events involving far field subduction plate collisions crustal thickening post collision collapse and rifting

dust transport and the question of desert loess formation although contemporary dust storms are frequent in arid and semi arid areas desert loess deposits are poorly developed much of the world s loess occurs in mid latitude areas which experienced glaciation during the pleistocene ocean core evidence indicates that dust transport from sub tropical deserts increased during cold stages of the pleistocene but loess formed only on certain desert margins for reasons which have not been fully explained this paper re examines the mechanisms of dust transport and deposition and the circumstances leading to the accumulation of thick loess typical loess is composed mainly of medium silt grains which are transported in short term suspension a few metres above the ground significant thicknesses of loess form only when dust is trapped within a limited area often relatively close to the source dust particles finer than 20 m are transported mainly in long term suspension over a greater height range and may be widely dispersed the availability of silt and the frequency magnitude and direction of dust transporting winds are important factors governing the potential for loess formation but the existence of a suitable dust trap is particularly important traps may be formed by topographic obstacles areas of moist ground or vegetated surfaces vegetation adjacent to glacial outwash plains and braided meltwater streams trapped dust in mid latitudes during the pleistocene dust blown during glacial periods from certain deserts notably in sinai soviet central asia and china accumulated as loess in neighbouring semi arid regions on the margins of other deserts loess formation was inhibited partly by the absence of vegetation traps during most of the holocene net dust deposition rates in all desert marginal areas have been too low for significant loess accumulation this is mainly due to a reduction in silt availability and a tendency towards landscape stability reported dust storm frequencies during the past 50 years over estimate the longer term holocene dust flux due to the effects of human activities much modern dust owes its origin to erosion of cultivated soils in semi arid areas and is finer than typical loess

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

relative importance of dust inputs and aquatic biological production as sources of lake sediments in an oligotrophic lake in a semi arid area the dustfall df and mass sedimentation rate msr in lake alchichica central mexico were studied from june 2006 to june 2008 df ranged between 0 11 0 93 g m 2 d 1 in the warm and rainy season and 0 54 1 21 g m 2 d 1 in the cold and dry season msr varied from 0 52 2 40 g m 2 d 1 in the stratification season to 1 14 5 07 g m 2 d 1 in the circulation season the timing of the highest fluxes of df and msr is most likely a product of several factors coinciding during the cold and dry season a availability of dust sources and the presence of strong winds 7 5 m s 1 in the df case and b the circulation period of the lake and the availability of nutrients in the msr case as expected the df in alchichica was high and similar to that found in other arid and semi arid areas however the msr was higher than that reported for other oligotrophic lakes particles captured in the aerial traps consisted mainly of detrital minerals in contrast particles found in the water traps were mostly biogenic and to a lesser extent detrital minerals the msr was one to seven times higher than the df in spite of the oligotrophic status of lake alchichica the large size of the settled phytoplankton autochthonous waterborne is what leads to the high msr which surpasses the df allochthonous airborne derived from whirlwinds originating in easily eroded terrains that are characteristic of arid semi arid areas our results indicate that caution must be taken in considering that the df amount measured through df collectors located at the lake shore does actually represent the df entering into the lake copyright 2010 john wiley sons ltd

geochronology and geochemistry of early middle triassic magmatism in the erguna massif ne china constraints on the tectonic evolution of the mongol okhotsk ocean abstract in this paper we present new zircon u pb dating hf isotope major and trace elements and sr nd isotope data for early middle triassic intrusive rocks in the erguna massif of ne china in the eastern segment of the central asian orogenic belt caob our aim is to elucidate the tectonic evolution of the mongol okhotsk ocean and its influence on ne china zircons from five representative intrusions in the erguna massif are euhedral subhedral in shape display oscillatory growth zoning in cl images and have th u ratios of 0 17 1 54 and in combination these features indicate that the zircons are of igneous origin zircon u pb dating results demonstrate that the early middle triassic magmatism in the erguna massif took place between 241 and 247 ma the early middle triassic rocks are composed mainly of a suite of diorites quartz diorites granodiorites monzogranites and syenogranites they have sio 2 57 71 72 86 wt mg 19 52 al 2 o 3 14 27 17 23 wt and na 2 o k 2 o 0 67 1 59 chemically they are metaluminous to peraluminous and belong to the high k calc alkaline series moreover they are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field strength elements e g nb ta and ti the whole rock e nd t and zircon e hf t values of these samples range from 4 68 to 3 42 and from 2 0 to 6 6 respectively indicative of formation from primary magmas generated by partial melting of juvenile crustal material with a contribution from mantle derived mafic magmas these magmas subsequently underwent fractional crystallization contamination and magma mixing geochemically these early middle triassic intrusive rocks have affinities with intrusive rocks from active continental margin settings we conclude therefore that the early middle triassic magmatism in the erguna massif was generated within an active continental margin setting related to the southwards subduction of the mongol okhotsk oceanic plate beneath the erguna massif this conclusion is supported by the occurrence of early mesozoic porphyry and skarn deposits along the southeastern side of the mongol okhotsk suture belt

loess in italy genesis characteristics and occurrence abstract there is currently a renewed interest in loess genesis and occurrence in italy well known loess profiles in northern italy have been re examined and previously unknown loess deposits in central and southern italy have been reported this work combines a meta analysis of published data with new data presented here for the first time to provide the state of the art on the spatial distribution characteristics genesis and deposition ages of loess in italy a database of 98 soil horizons from 91 soil profiles was created and made available it stores information on soils formed from loess or containing layers that show admixture of loess soil data include the source of information the topographic geomorphological and geological setting kind of parent material and land use main soil horizon properties as described in the field soil classification particle size distribution and chemical data loess is reported from almost all regions of italy it is generally pedogenized throughout the entire loess body and forms the parent material of deep and complex soil profiles the thickness of the loess deposits varies from a few decimeters to a few meters pedogenesis and local reworking partially change the original loess characteristics in this study we propose a set of parameters that help recognizing loess in soils particle size distribution and sorting geomorphological setting pedostratigraphic position shape of the grains under optical and scanning electron microscope sem and soil micromorphological characteristics the ages of the loess deposits range between 70 ka bp and 18 ka bp there are also a number of samples that have been dated to the holocene the meta analysis suggests that climate is not the only driver of loess deposition in italy geomorphological instability and human disturbance as well as the influence of saharan dust most likely played major roles too this study demonstrates that loess is much more widespread in italy than previously estimated yet further research on the spatial and temporal distribution of loess deposition across the mediterranean region is needed to better understand its genesis sources and trajectories periods of enhanced loess formation and the role of loess deposits in ecosystem functioning and resilience

a novel mineralogical approach for provenance analysis of late quaternary marine sediments the case of myrtoon basin and cretan sea aegean greece abstract sediments from two deep sea bottom cores from the myrtoon basin in the sw aegean sea and eastern cretan sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and climatic conditions and palaeo environmental control on sediment deposition both cores contain calcareous muds and silts with dark olive grey organic rich intervals corresponding to the regional sapropel s1 horizon the presence of a few tephra layers documents volcanic activity in the southern part of the aegean sea the bulk sediments contain abundant carbonate minerals mainly calcite and mg calcite and clay minerals mainly illite and smectite and accessory serpentine talc and hornblende which attest to contributions from ultrabasic sources there is a sharp decrease of the mg calcite content and the mg ca ratio of the carbonate fraction in sapropelic sediments followed by an increase of the average grain size a well expressed negative relationship between illite and smectite was observed in the clay fraction in full accordance with previous studies however this trend is absent from the bulk sediments because smectite is significantly overestimated in the oriented clay fractions clay mineral distribution is controlled mainly by sediment sorting with deposition in the sapropelic sediments being also affected by climatic changes the different types of smectite in the cores and the presence of smectite with high dehydroxylation temperature in the se aegean suggests that the sediment supply from se mediterranean sources should be limited

magma mixing recharge and eruption histories recorded in plagioclase phenocrysts from el chichon volcano mexico operative throughout the 200 ky history of the el chichon magma consistent core to rim decreases of sr sr ratios and coincident system increases in sr concentrations in plagioclase phenocrysts of varying size 1 cm to 2 mm are reported from samples of the 1982 and pre 1982 200 ka eruptions of el chichon volcano maximum sr sr ratios of 0 7054 significantly higher than the wholerock isotopic ratios 0 7040 0 7045 are found in the cores

sm nd dating and ree composition of scheelite for the honghuaerji scheelite deposit inner mongolia northeast china abstract sm nd analyses of seven scheelite samples from scheelite quartz veins in the honghuaerji scheelite deposit produce a well defined linear array on an isochron diagram with a mean square weighted deviation mswd of 0 87 corresponding to an age of 178 4 2 9 ma with end t 1 50 this age is interpreted to represent the age of scheelite mineralization the scheelite sm nd age is in good agreement with u pb ages obtained from a mineralization related granite 179 4 178 6 ma indicating that there is no apparent age gap between granite crystallization and ore formation rare earth element ree abundances in the scheelite were determined by in situ laser ablation inductively coupled plasma mass spectrometry la icp ms and the scheelite samples contain elevated ree concentrations with total ree y contents in the range of 3339 to 6321 ppm the chondrite normalized ree distribution patterns of all scheelites are middle ree mree enriched with strong negative eu anomalies eu eu 0 09 0 23 the ree characteristics of the honghuaerji scheelite suggest that ree 3 substituted into the ca site along with na and nb dominated by na whereas eu is predominantly present as eu 2 in the scheelite and may have crystallized from relatively reduced fluids all sulfur isotope data 34 s for sulfide separates range from 2 0 to 3 8 with an average of 3 2 measured 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios vary from 18 243 to 18 451 15 494 to 15 574 and 37 933 to 38 340 respectively on the basis of common sr nd pb hf isotopic characteristics between the scheelite and the host granite and the positive initial nd isotope ratios 1 46 1 52 low 87 sr 86 sr ratios 0 704983 0 705297 in the scheelites it is inferred that the hydrothermal fluids responsible for tungsten mineralization at honghuaerji were of magmatic origin with a mantle derived signature based on the regional geology tectonic evolution and geochemical evidence the honghuaerji granite is thought to have been derived from the partial melting of thickened lower crust produced during post collisional orogenic events associated with the closure of the mongol okhotsk ocean

the potential influence of dust flux and chemical weathering on hillslope morphology convex soil mantled carbonate hillslopes in the eastern mediterranean abstract convex soil covered hillslopes are ubiquitous in various tectonic and climatic settings and their morphologic characteristics can be significantly altered by dust flux and chemical weathering carbonate hillslopes across the eastern mediterranean display a classic convex morphology despite high rates of dust deposition which are apparently similar in magnitude to denudation rates and despite a highly soluble bedrock lithology these high rates of dust flux and bedrock dissolution result in soil composition which is strikingly different from the underlying bedrock in this study we apply a modified regolith mass balance equation which includes dust input and chemical depletion and utilize a combination of field work and geochemical methods immobile and major elements xrd to estimate the fraction of dust derived materials in the soil and the fraction of the soil that was lost via dissolution soil and bedrock were sampled at 7 eastern mediterranean study sites across a prominent north to south gradient in both precipitation 250 to 900 mm yr 1 and dust flux 150 to 40 g m 2 yr 1 and compared with dust composition our results indicate that the dust fraction in the soil correlates with modern measurements of dust deposition rates and decrease from nearly 100 of the 2 mm indicating that mechanical weathering of the underlying bedrock contributes to regolith formation and plays a role in shaping carbonate hillslopes using a commonly used soil transport model we show that the observed dust fraction and chemical weathering can potentially account for a 50 change in hillslope curvature furthermore the predicted steady state hilltop curvature based on our results fits well the observed curvature based on high resolution lidar derived topographic data our results highlight the potential importance of dust and chemical weathering in soil production formulations and hillslope evolution models and we propose that these contributors to soil mass balance could also be relevant for silicate terrain in addition we also demonstrate that the source material of mediterranean soils varies with environmental factors such as rainfall dust deposition rates and bedrock mechanical properties

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

geochronological and geochemical constraints on the genesis of the huanren skarn cu zn deposit northeast china abstract the huanren skarn cu zn deposit is located in southeastern liaoning on the eastern edge of the north china craton ncc in this paper we present a study on the geochronologic geochemical and sr nd hf and s isotopic data for the magmatic rocks and sulfide minerals exposed in the deposit laser ablation inductively coupled plasma mass spectrometry la icp ms dating of zircon grains from two mining pits in the monzodiorite yields ages of 128 2 1 1 ma and 128 6 1 5 ma these results indicate that the magmatism in the huanren cu zn deposit might have occurred in the early cretaceous geochemically the huanren monzodiorite belongs to the high k calc alkaline and shoshonitic series is enriched in rb ba and k and is depleted in nb ta and ti the rocks also have relatively high 87sr 86sr i 0 7091 0 7099 and low end t 13 2 to 10 3 and ehf t values 14 3 to 7 8 the sr nd hf isotopic data for the monzodiorite indicate that the magma may be derived from mixed sources of the crust and mantle the 34s values of chalcopyrite galena and pyrite range from 4 4 to 5 8 with an average of 5 1 indicating that the sulfur in the deposit was mainly derived from a magmatic source the huanren cu zn deposit resulted from the magmatism and mineralization induced by the rollback of the paleo pacific plate

the role of african dust in the formation of quaternary soils on mallorca spain and implications for the genesis of red mediterranean soils abstract african dust additions explain the origin of terra rossa soils that are common on the carbonate platform island of mallorca spain mineralogical and geochemical analyses indicate that quaternary carbonate eolianites on mallorca have a very high purity usually composed of more than 90 carbonate minerals calcite dolomite and aragonite in contrast terra rossa soils developed on these eolianites have lower carbonate contents and contain higher concentrations of quartz and other silicates analyses of immobile trace elements indicate that the non carbonate fractions of the eolianites have distinctive zr hf la yb cr sc and th ta values that differ from the superjacent terra rossa soils these observations indicate that even if sufficient dissolution of the eolianite had taken place to create the soils by residual accumulation immobile element ratios in the soils require an external source however zr hf la yb cr sc and th ta values in the soils fall within the range of values for these element ratios in african dust collected on barbados and mainland spain we conclude that the silicate fractions of terra rossa soils on mallorca are derived mainly though not wholly from far traveled african dust and this process may explain the origin of other terra rossa soils found in southern europe

eolian dust deposition on the giara di gesturi basalt plateau sardinia mineralogical study of samples from depression fills on an isolated basalt plateau in central sardinia showed that although the basalt is free of quartz and mica fair amounts of these minerals occur in the finer fractions results from x ray analyses of silt fractions and morphoscopical analyses of sand fractions indicate that the bulk of the quartz and mica is of eolian origin the eolian quartz is predominantly of medium and coarse silt size and in the upper 10 cm of the depression fills constitutes about 20 per cent of the soil mass approx 20 kg m2 eolian mica is present in smaller amounts and is of medium silt or smaller size the provenance of the eolian material could not be established with certainty although a local origin can be excluded

an extended episode of early mesoproterozoic metamorphic fluid flow in the reynolds range central australia the products of metamorphic fluid flow are preserved in zones within the marbles and metamorphosed semipelites of the upper calcsilicate unit in the granulite portion of the late palaeoproterozoic reynolds range group northern arunta block central australia the zones of retrogression characterized by minerals such as wollastonite grossular and clinohumite local resetting of oxygen isotopic compositions and local major element metasomatism were channelways for water rich fluids derived from granulite facies metapelites u th pb isotopic ages measured by the shrimp ion microprobe on zircon and monazite from a granulite facies semipelite an early semiconcordant aluminous quartz rich fluid flow segregation and a late discordant quartz rich segregation record some of the extended thermal history of the area zircon cores from the semipelite show its likely protolith to be an igneous rock 1812 11 ma old itself derived from a source containing zircon as old as 2 2 ga low th u overgrowths on the zircon grew during granulite facies metamorphism at 1594 6 ma monazite cooled to its blocking temperature at 1576 8 ma zircon cores from the semiconcordant segregation are dominantly 2 3 ga old indicating that the source of the fluids was not the particular metamorphosed semipelite studied two generations of low th u overgrowths on the zircon give indistinguishable ages for the older and younger of 1589 8 and 1582 8 ma respectively the monazite age is the same 1576 12 ma zircon from the late discordant segregation gave 1568 4 ma fluid flow occurred for at least 18 3 ma and ended 26 3 ma after the peak of metamorphism suggesting a very slow cooling rate of 3 c ma 1 the last regional high grade metamorphism in the reynolds range occurred at 1 6 ga not 1 78 ga as previously thought the high grade event at 1 78 ga is a separate event that affected only the basement to the reynolds range group

petrogenesis of archaean trondhjemites tonalites and granodiorites from eastern finland major and trace element geochemistry

tephra in caves distal deposits of the minoan santorini eruption and the campanian super eruption abstract tephra deposits in caves are not only significant as stratigraphic markers the comparatively sheltered position of cave environments protected from rainfall may preserve original distal tephra deposition features unlikely to have survived in the open landscape most reported findings of tephra in caves are from the campanian super eruption which originated in the area of naples italy these findings facilitate evaluation in different caves of facies variability and modes of tephra deposition derived from the same eruption the campanian volcanic event about 40 000 years ago was the largest eruption in europe and the mediterranean region during the late pleistocene another major volcanic event during the quaternary was the more recent santorini eruption in the eastern mediterranean aegean sea during the late minoan cultural period approximately 3600 years ago this was the largest holocene eruption in the region but tephra deposits in caves from this event appear to be very rare we present here the first ever finding of a visible tephra layer from the minoan santorini eruption in a cave the pure tephra situated in the pelekita cave in eastern crete near kato zakros has a thickness of up to 9 cm geochemistry analyses of major elements by electron probe micro analysis epma and trace elements by laser ablation inductively coupled plasma mass spectrometry la icp ms prove the tephra to be derived from the minoan santorini eruption radiocarbon dating also fits the time frame of this eruption our findings indicate that the tephra layer in the pelekita cave is an air fall deposit the lower boundary of the tephra layer is sharp and wavy draping over the underlying irregular cave surface particle size distribution of the tephra is bimodal and typical for suspended aeolian transport the consistently smaller size of heavier feldspar particles adjacent to larger but lighter volcanic glass particles in thin sections of undisturbed samples corroborate emplacement of the tephra inside the pelekita cave from high altitude fallout

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

computing earthquake probabilities on global scales large devastating events in systems such as earthquakes typhoons market crashes electricity grid blackouts floods droughts wars and conflicts and landslides can be unexpected and devastating events in many of these systems display frequency size statistics that are power laws previously we presented a new method for calculating probabilities for large events in systems such as these this method counts the number of small events since the last large event and then converts this count into a probability by using a weibull probability law we applied this method to the calculation of large earthquake probabilities in california nevada usa in that study we considered a fixed geographic region and assumed that all earthquakes within that region large magnitudes as well as small were perfectly correlated in the present article we extend this model to systems in which the events have a finite correlation length we modify our previous results by employing the correlation function for near mean field systems having long range interactions an example of which is earthquakes and elastic interactions we then construct an application of the method and show examples of computed earthquake probabilities

early jurassic porphyry copper mineralization in ne china a case study of the yanghuidongzi deposit abstract the yanghuidongzi cu deposit is located in the southeastern part of heilongjiang province in ne china and represents one of the few known early jurassic porphyry cu deposits within the eastern edge of the xing an mongolia orogenic belt here we present new whole rock major and trace element and sr nd isotopic data zircon u pb and hf isotopic data and molybdenite re os data for units associated with the deposit laser ablation inductively coupled plasma mass spectrometry la icp ms dating of zircons from the granodiorite porphyry in the study area yielded ages of 191 0 1 1 and 191 2 1 0 ma that are interpreted to be the emplacement age of this intrusion the molybdenite re os dating undertaken during this study yielded model ages of 192 7 187 0 ma an isochron age of 188 2 3 8 ma and a weighted mean model age of 190 2 2 6 ma representing the timing of formation of the cu mineralization in this area the yanghuidongzi granodiorite porphyry contains relatively high concentrations of sio 2 68 88 72 49 wt al 2 o 3 15 37 16 31 wt and sr 230 479 ppm but relatively low concentrations of y 7 97 9 87 ppm and yb 0 72 0 85 ppm suggesting that this intrusion has an adakitic affinity combining this with the positive end t 0 7 1 1 and ehf t values 4 0 6 9 low mg values 41 50 and the low concentrations of mgo 0 86 1 22 wt cr 3 17 4 37 ppm and ni 2 11 4 20 ppm within this intrusion suggests it formed from a magma generated by the partial melting of juvenile lower crustal material during the early jurassic subduction of the paleo pacific plate

a luminescence dating study of open air palaeolithic sites in western epirus greece we report results of a preliminary luminescence dating study of middle to late pleistocene red beds and early holocene dune deposits from prehistoric sites in northwest greece the wide range in age estimates contradicts the impression that all the red sediments of the region are as old as the pliocene or early pleistocene and that artefacts found in them are late intrusions and hence worthless in a stratigraphic context our data provide support for a recently proposed chronological framework of the palaeolithic in the region tl irsl comparisons confirm the irsl as a more appropriate means for dating water laid deposits while both methods appear to be equally useful for aeolian sediments the study cautions that the effect of various laboratory procedures used to obtain tl or irsl dates in a context of complex depositional histories precludes a simple prima facie interpretation of the ages a proper evaluation of luminescence dates requires a full account of the laboratory procedures employed and an understanding of the depositional history of the sediments

dust transportation and deposition in a superhumid environment west coast south island new zealand contemporary rates of dust deposition monitored along a 300 km section of the superhumid west coast of new zealand s south island are presented in this setting dust is entrained primarily from the dry channels of braided glaciofluvial rivers that drain the western slopes of the southern alps measured dust deposition ranged between 0 21 and 118 9 kg 1 ha 1 month 1 which is similar to dust deposition rates monitored in arid and semiarid environments however these are not considered to be sufficient for present day loess genesis dust deposition was highest in summer because of the greater frequency of favourable dust transporting winds and the effect of rainfall was secondary dust transportation occurred mainly during the passage of nonprecipitating cold fronts or postfrontal southwesterlies transportation also occurred during prefrontal conditions and in winter fohn southeasterlies were the predominant dust transporting winds to affect the west coast

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

geochronology and geochemistry constraints of the early cretaceous taibudai porphyry cu deposit northeast china and its tectonic significance abstract the southern great xing an range sgxr located in the southeastern part of inner mongolia china shows intense mesozoic tectono magmatic activity and hosts economically important polymetallic cu pb zn sn fe ag au mo mineralization here we present new zircon u pb ages whole rock geochemical data nd sr hf isotopic data and re os ages for the taibudai deposit in the sgxr the taibudai granitoids show high sio2 70 62 72 13 wt and alkali na2o k2o 7 04 8 60 wt concentrations low mgo 0 89 1 37 wt and al2o3 14 wt asi ratios

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

distribution of clay minerals in surface sediments of the aegean sea a compilation extensive published data sets and some new data on the clay mineral composition of surface sediments in the aegean sea northeastern mediterranean sea have been compiled in order to map the distribution patterns of clay mineral assemblages and to decipher source areas and transport paths we distinguished six provinces a northwest aegean province a marmara dardanelles province a west turkey province a southeast aegean province a kithira province and a central aegean province the clay mineral assemblages in the coastal and shelf areas carry the signature of the riverine sediment discharge from southeast europe and turkey respectively the southern aegean sea is probably influenced by the river nile discharge and transport of clay minerals by surface currents the clay minerals in the central aegean sea form a mixed assemblage comprising components of the other assemblages a dispersion and dilution of clay minerals by surface currents is obvious

re os isotopic dating of molybdenites in the xiaoliugou w mo deposit in the northern qilian mountains and its geological significance abstract the xiaoliugou is a large scale w mo deposit newly explored in the northern qilian mountains caledonian fold belt northwestern china it is a vein and skarn type deposit genetically associated with the xiaoliugou caledonian granodiorite stock re os isotopic dating for the molybdenite in the deposit yields an isochron age of 462 13 ma 2 and model ages of 436 to 496 ma these results suggest that w mo mineralization occurred before the collision of plates and mineralized substances mainly originated from the crust

controls on different mineralization styles of the dongbulage mo and taibudai cu mo porphyry deposits in the great xing an range ne china abstract the dongbulage porphyry mo dominant and taibudai cu mo deposits are located in the central southern great xing an range inner mongolia northeastern china and are associated with granite porphyry and monzogranite intrusions respectively re os isotope data for five molybdenite samples from the dongbulage mo deposit give a weighted mean model age of 164 3 1 2 ma which is in accordance with a zircon u pb age of 164 5 1 7 ma for the host granite porphyry indicating that the deposit formed at the end of the middle jurassic the zircon u pb age of the taibudai ore bearing monzogranite is 137 9 1 7 ma indicating that the deposit formed in the early cretaceous whole rock geochemical data indicate that the dongbulage granite porphyry and the taibudai monzogranite are high k calc alkaline and have ree patterned light rare earth elements lrees enriched and heavy rare earth elements hrees depleted both plutons show ba nb and ti depletions on normalized trace element diagrams and the dongbulage granite porphyry shows strongly negative eu anomalies which are absent in the taibudai intrusion the geochemical differences between the two intrusions suggest that the dongbulage granite porphyry is the result of more advanced fractional crystallization which led to the formation of a mo dominant deposit whereas the lesser degree of crystal fractionation in the taibudai monzogranitic magma resulted in the formation of a cu deposit the relatively listric shaped ree patterns of taibudai rocks suggest more hydrous parental magmas than that of dongbulage rocks therefore fractional crystallization and magma water content exert a significant control on the styles of mineralization mo versus cu dominant in the central southern great xing an range

aeolian dust transport and deposition over crete and adjacent parts of the mediterranean sea monitoring of dust deposition at several stations on crete over a three year period has shown that the present day depositional flux is of the order of 10 100 gm 2 yr 1 most of the dust deposition takes place during a few annual dust events which typically last for 1 3 days dust haze episodes are usually associated with southerly or southwesterly winds which transport fine sediment from north africa dust is raised by a wide variety of meteorological conditions which generate strong near surface winds in the source areas but major long range transport events are often associated with cold fronts linked to the passage of deep mid latitude depressions during winter and spring dust haze frequency and deposition rates are highest in western crete and decrease towards the east suggesting that transport from tunisia and neighbouring parts of north africa is particularly important the measured rate of dust deposition is well below the minimum level required for loess formation deposits which have previously been identified as loess are shown to be uncemented marine marls of tertiary age laboratory analysis of red soils surface sediments and bedrock samples has confirmed that many of the soils contain an important aeolian dust component but it is concluded that a more important source of soil parent material is provided by weathering of local rocks many of the soils contain significant amounts of quartz sand which cannot have been transported across the sea from north africa reworking of weathered material and deposited dust is extensive and is accomplished by both aeolian and fluvial processes tectonically controlled depressions in the mountains and parts of the coastal lowlands have acted as long term sinks in which a thickness of several metres of sediment and soil has accumulated during the quaternary

mineralogy chemistry and palaeoenvironmental significance of an early tertiary terra rossa from northern ireland a preliminary review abstract early tertiary basalts of the antrim plateau have preserved palaeosols developed on late cretaceous limestone these palaeosols include dark red clays and clays with flints that are rich in silica and contain a complex clay mineral assemblage of 2 1 lattice clays kaolinite and sepiolite they occur in infilled solution hollows and joints can be associated with a rudimentary tower karst and are similar in appearance and composition to present day mediterranean terra rossa soils elsewhere grey flint rich clay sized material dominated by silica and kaolinite developed on an undulating landscape sometimes now capped by a lignite horizon deposits and the palaeolandscape suggest a humid tropical to sub tropical environment contrary to previous published inferences of arid conditions but corresponding to humid tropical conditions proposed for the formation of overlying inter basaltic soils

crustal block movements from holocene shorelines crete and antikythira greece abstract marks of several shorelines left by sea level stands during the last 4000 yrs occur along the coasts of the islands of crete and antikythira in this area recent movements of the earth s crust were identified by using a systematic survey based on multidisciplinary analyses strengthened by 60 radiometric datings between 4000 and 1700 yr b p a block of lithosphere a about 150 km long fig 10 which included antikythira and the levka mountains in crete underwent a series of ten rapid subsidences from 10 to 25 cm each time without noticeable tilting these movements ended about 1 530 40 yr b p a further block of lithosphere b approximately 200 km long was then uplifted about 10 m and inclined northeastwards in a single event block b includes block a and extends 50 km further eastwards beyond the ida mountains as far as the iraklion sedimentary basin the tectonic movements were preceded by vertically reversed displacements of short duration on at least three occasions if the a block subsidences can be ascribed to gravitational forces then the b block uplift suggests a cause that originated at depth crustal consumption and elastic rebound to the east of the ierapetra graben the sitian peninsula appears to belong to a block of lithosphere c affected by a northeast tilting and separated by an active fault from the crustal block of khrisi koufonisi

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

recycling of orogenic arc crust triggers porphyry cu mineralization in kerman cenozoic arc rocks southeastern iran pre collisional eocene oligocene arc diorites quartzdiorites granodiorites and volcanic equivalents in the kerman arc segment in central iran lack porphyry cu mineralization and ore deposits whereas collisional middle late miocene adakite like porphyritic granodiorites without volcanic equivalents host some of the world s largest cu ore deposits petrological and structural constraints suggest a direct link between orogenic arc crust evolution and the presence of a fertile metallogenic environment ore hosting kuh panj porphyry intrusions exhibit high sr 400 ppm low y 20 no negative eu anomalies eu eu 1 and relatively non radiogenic sr isotope signatures 87sr 86sr 0 7042 0 7047 relative to eocene oligocene granitoids mainly sr 12 la yb 15 eu eu 1 87sr 86sr 0 7053 0 7068 trace element modeling indicates peridotite melting for the barren eocene oligocene intrusions and a hydrous garnet bearing amphibolite source for middle late miocene ore hosting intrusions the presence of garnet implies collisional arc crustal thickening by shortening and basaltic underplating from about 30 35 to 40 45 km or 12 kbar the changes in residual mineralogy in the source of eocene to miocene rocks in the kerman arc segment reflect probing of a thickening arc crust by recycling melting of the arc crustal keel underplating of cu and sulfur rich melts from fertile peridotite generated a fertile metallogenic reservoir at or near the crust mantle boundary and dehydration melting under oxidizing conditions produced syn and post collisional ore hosting intrusions while the lack of post collisional volcanism prevented the venting of volatiles to the atmosphere from sulfur rich and oxidized adakitic magmas

characterization of aerosols in marine environments mediterranean red sea and indian ocean a study of the aerosol in different marine environments was performed during a scientific cruise on the vessel salermum from the mediterranean sea to the indian ocean january 1 to february 27 1979 the aerosol particles were sampled on membrane filters and in a single stage impactor the particles on the filters were analyzed for soluble mg ca k na for mineral aerosol mass concentration and for chloride particles an elemental analysis using the microprobe attached to the scanning electron microscope sem was carried out the aerosol particle size distribution was determined from the photographs of the filter surface taken by the sem the concentration of the ice forming nuclei was measured by developing the filters in a static diffusion chamber chloride particles were also independently detected on the single stage impactor slides the data also discussed in association with the atmospheric turbidity measurements taken during the same cruise give a clear picture of the aerosol characteristics which reflect in a detailed and sensitive way the origin of the air mass in which they were sampled

age tectonic setting and metallogenic implication of phanerozoic granitic magmatism at the eastern margin of the xing an mongolian orogenic belt ne china abstract the eastern margin of the xing an mongolian orogenic belt is characterised by widespread phanerozoic granitic magmatism some of which is closely related to significant ore mineralisation this paper presents new geochronological petrogenetic and tectonic data for selected intrusions zircon u pb geochronology for five granitoid plutons indicates they were emplaced during the middle late permian 264 255 ma and cretaceous 106 94 ma and thus granitic magmatism occurred throughout the phanerozoic permian 268 252 ma early middle triassic 248 240 ma early jurassic 183 ma and cretaceous 112 94 ma the permian granitoids consist of monzogranite granodiorite tonalite and quartz diorite characterised by enrichment in na2o 3 60 4 72 wt depletion in k2o 0 97 2 66 wt and a negative correlation between p2o5 and sio2 together with the presence of hornblende these geochemical features are indicative of an i type affinity the permian granitic magmatism is associated with quartz vein type tungsten deposits 252 ma unpublished sm nd isochron age which formed in an active continental margin setting related to subduction of the palaeo asian ocean the cretaceous quartz diorites have an adakitic affinity having relatively high sr 374 502 ppm low yb 0 51 0 67 ppm and y 8 7 10 7 ppm and high sr y 39 4 46 8 and la yb n values 16 2 34 7 suggesting that they were related to the partial melting of subducted oceanic crust in addition they are associated with porphyry au cu deposits we conclude that the cretaceous granitic rocks and associated porphyry au cu mineralisation occurred in an extensional tectonic setting related to the subduction of the palaeo pacific plate beneath the eurasian plate in addition the large scale early middle triassic syn collisional granite belt at the eastern margin of the xing an mongolian orogenic belt extends from the middle of jilin province to the wangqing hunchun region constraining the timing of the final collision between the north china craton and the jiamusi khanka massif and suggesting that the xra moron river changchun suture likely extends eastward into the eastern hunchun region this collision caused the middle triassic mesothermal lode gold mineralisation

the early cretaceous weilasituo zn cu ag vein deposit in the southern great xing an range northeast china fluid inclusions h o s pb isotope geochemistry and genetic implications abstract the weilasituo vein type deposit hosted in hercynian middle to late paleozoic quartz diorite and palaeozoic gneiss occurs on the western slopes of the southern great xing an range in this paper we present results from fluid inclusion and isotope h o s pb investigations on the weilasituo deposit we identify three stages during the ore formation a barren pre ore stage stage 1 a main ore stage with economic grade cu zn ag mineralization stage 2 and a barren post ore stage stage 3 fluid inclusion and mineral thermometry constrain temperature intervals of approximately 243 to 333 c 192 to 425 c and 141 to 261 c for the three stages respectively fluids in the main ore stage are characterized by complex nacl h 2 o ch 4 co 2 low salinity 3 55 to 8 68 wt nacl equiv with isotopic signatures consistent with a magmatic source these fluids evolved by mixing with local meteoric water 18 o fluid 1 15 to 5 15 d fluid 139 4 to 88 2 measured and calculated sulfur isotope compositions of hydrothermal fluids 34 s fluid 3 0 to 3 4 indicate that the ore sulfur was derived mainly from a magmatic source the lead isotope ratios from the ores show mean values of 18 326 15 553 and 38 242 for 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb respectively indicating a mantle source our study shows that fluid mixing and or dilution played an important role in copper zinc and silver mineralization in the weilasituo deposit the weilasituo and bairendaba deposits represent a linked ore system genetically related to the late mesozoic magmatism the ore forming fluids associated with the early cretaceous mineralization in the southern great xing an range are of magmatic in origin and evolved by mixing with local meteoric water these deposits preserve the signature of a mantle source for lead however the deposits formed at ca 177 160 ma possess a dominantly magmatic signature with less radiogenic lead

dry aeolian dust accumulation in rocky deserts a medium term field experiment based on short term wind tunnel simulations the spatial pattern of medium term a few months dry aeolian dust accumulation in rocky deserts is predicted using short term deposition and erosion experiments in a wind tunnel the predictions are tested in a field experiment set up in the northern negev desert of israel the results show that superimposing wind tunnel deposition and erosion maps usually leads to correct predictions of medium term dust accumulation the predictions are somewhat less confident near the inflection lines of windward hillslopes where small scale irregularities in the local topography make it difficult to locate the exact position of the areas of little accumulation elsewhere in the topography predictions are good and the method works satisfactorily highest accumulation occurs on concave windward slopes and to a lesser extent on slopes parallel to the wind little accumulation occurs on the convex windward slopes and in dust separation bubbles the smallest accumulation rates are observed immediately upwind of the top of pronounced hills and on leeslopes the rate of dry dust accumulation measured during the field experiment varied from 17 to 93 g m 2 a 1 depending on the topographic position of the accumulation plots for most plots it was of the order of 30 60 g m 2 a 1

soil types and eolian dust in high mountainous karst of the northern calcareous alps zugspitzplatt wetterstein mountains germany abstract this study deals with the soil formation on pure limestone in the high mountainous karst of wetterstein mountains northern calcareous alps the study area in detail covers the alpine 2000 to 2350 m and the subnivale zone 2350 to 2600 m of zugspitzplatt a tertiary paleosurface situated next to the highest summit of germany zugspitze 2963 m the formation of autochthonous soils is determined by the following parameters uniform geology and geochemistry of triassic limestone caco3 mgco3 98 variable substrata solid rock debris local moraine hypsometric pattern of vegetation modified by microclimate and aspect variety of micro environments in karst relief in the subnivale zone only leptosols lithic skeletic and regosols calcaric humic occur whereas in the alpine zone different stages of folic histosols and rendzic leptosols prevail due to the diversity of vegetation the purity of limestone prevents a distinct contribution of residues to soil formation instead of expected a b c profiles the residues are mixed with organic matter of folic horizons o ob c only in karst depressions or on local moraines small bt horizons 2 to 5 cm occur they mark a developed stage of folic histosol o ob bt c representing the climax of autochthonous mineral soil genesis in the study area special features are brown deposits mean thickness 30 cm covering large parts of the alpine zone on the basis of mineralogical x ray diffraction heavy minerals and pedological data grain size soil chemistry eolian origin is indicated the resulting soils are classified as loess loam like cambisols ah bw 2 bt 2c and are related to late glacial loess deposition egesen stade of younger dryas the abundance of mica and silt in the surface layers and the grain size distribution of snow dust samples prove that dust influx by southerly winds is still continuing the major sources for both late glacial and present day dust are magmatic and metamorphic rock formations of the central alps additionally local dust transport from adjacent outcrops of jurassic and lower cretaceous sediments is evident

the geochemical characteristics of granitoids in contrasting arcs and comments on magma sources geochemical variations in modern subduction related igneous suites with respect to arc maturity in time and space are illustrated using data for both volcanic suites basalt andesite and dacite and intrusive granitoid suites diorite tonalite granodiorite and granite from circum pacific arcs using trace element data we suggest that two groups of processes control the natural variation in the parental magmas of both suites a subduction zone enrichment of lithospheric mantle locally coupled with crustal assimilation allied with fractional crystallization afc in zones of thickened crust all of which yield magmas with enhanced concentrations of the large ion lithophile lil elements k rb th u lrees etc b with increasing distance from the active trench contributions from within plate sub continental lithosphere producing mantle derived magmas with enhanced levels of high field strength hfs elements among which nb ta hf and y are particularly distinctive thus even for the evolved granitoids of intrusive arc series ratios of hfs lil elements not significantly affected by crystal fractionation such as ta nb k rb la may throw some light on the origin of mafic intermediate precursor magmas in terms of these elements we suggest the following groupings for interpreting the tectonic associations of granitoid suites 1 primitive calcic arc granitoids with low lil and hfs element abundances 2 normal calc alkaline continental arc granitoids with enhanced lil element abundances and low hfs lil ratios 3 mature alkali calcic arc granitoids with high levels of lil and hfs elements and higher hfs lil ratios 4 back arc anorogenic alkaline granitoids with the highest levels of hfs elements

glacial comminution of quartz sand grains and the production of loessic silt a simulation study abstract traditional views have attributed the formation of loess sized quartz silt particles to glacial processes glacial grinding was considered to be the only mechanism capable of producing loessic silt in the quantities necessary for the formation of loess deposits this idea has been strengthened by the apparent close association between present or former glacierised regions and major global loess deposits however some doubts exist as to whether or not glacial grinding is capable of producing sufficient quantities of quartz silt because of the difficulties entailed in the observations and direct measurement of subglacial abrasion and crushing this paper describes and discusses the results of a simulation study designed to examine abrasion and size reduction of quartz grains under grinding conditions analogous to those experienced in a subglacial environment the findings from these experimental runs suggest that although particle breakage and comminution does occur little silt sized material is actually produced the amount of silt produced ranges from approximately 9 of the original sample in one experimental run to less than 1 for the other seven runs it is suggested that the results obtained may show considerably less abrasion and loessic silt production than may be expected to occur within a natural subglacial environment because 1 subglacial grains experience much greater overburden pressures for much longer periods of time 2 the use of sand sized grains may represent a stable component resistant to further size reduction through crushing or abrasion and 3 the use of a monomineralic sample of relatively sound quartz grains although care must be taken when relating results obtained from these experimental runs to silt production within a glacial environment findings from this work do question whether large amounts of quartz silts are produced within subglacial environments the importance of glacial processes in the formation of loess deposits may lie in the reworking of pre existing sediments by ice rather than the actual production of vast quantities of silt this in turn suggests that care should be taken in the interpretation of the provenance of particles comprising loess deposits

an exceptionally thick middle pleistocene tephra layer from epirus greece abstract a newly recognized 2 m thick trachytic volcanic ash deposit from northwestern greece is dated at 374 000 7000 yr and correlated with the middle pleistocene volcanic activity of central italy the deposit represents ash fallout from one of the largest volcanic eruptions in europe of the past 400 000 yr and should provide an important stratigraphic marker within the poorly dated middle pleistocene deposits of italy and greece

modern and late quaternary clay mineral distribution in the area of the se mediterranean sea the present day clay mineral distribution in the southeastern levantine sea and its borderlands reveals a complex pattern of different sources and distribution paths smectite dominates the suspended load of the nile river and of rivers in the near east illite sources are dust bearing winds from the sahara and southwestern europe kaolinite is prevalent in rivers of the sinai in egyptian wadis and in saharan dust a high resolution sediment core from the southeastern levantine sea spanning the last 27 ka shows that all these sources contributed during the late quaternary and that the nile river played a very important role in the supply of clay nile influence was reduced during the glacial period but was higher during the african humid period in contrast to the sharp beginning and end of the african humid period recorded in west african records 15 and 5 5 ka our data show a more transitional pattern and slightly lower nile river discharge rates not starting until 4 ka the similarity of the smectite concentrations with fluctuations in sea surface temperatures of the tropical western indian ocean indicates a close relationship between the indian ocean climate system and the discharge of the nile river

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

petrology of the chilliwack batholith north cascades washington generation of calc alkaline granitoids by melting of mafic lower crust with variable water fugacity calc alkaline granitoid rocks of the oligocene pliocene chilliwack batholith north cascades range from quartz diorites to granites 57 78 sio2 and are coeval with small gabbroic stocks modeling of major element trace element and isotopic data for granitoid and mafic rocks suggests that 1 the granitoids were derived from amphibolitic lower crust having ree rare earth element and sr nd isotopic characteristics of the exposed gabbros 2 lithologic diversity among the granitoids is primarily the result of variable water fugacity during melting the main effect of fh 2 o variation is to change the relative proportions of plagioclase and amphibole in the residuum the ree data for intermediate granitoids quartz diorite granodiorite eu eu 0 84 0 50 are modeled by melting with fh 2 o 1 kbar leaving a plagioclase pyroxene residuum in contrast data for leucocratic granitoids leuco granodiorites and granites eu eu 1 0 0 54 require residual amphibole in the source and are modeled by melting with fh 2 o 2 3 kbar consistent with this model isotopic data for the granitoids show no systematic variation with rock type 87sr 86sri 0 7033 0 7043 end 0 3 3 to 5 5 and overlap significantly with data for the gabbroic rocks 87sr 86sri 0 7034 0 7040 end 0 3 3 to 6 9 the fh 2 o variations during melting may reflect additions of h2o to the lower crust from crystallizing basaltic magmas having a range of h2o contents chillwack gabbros document the existence of such basalts one dimensional conductive heat transfer calculations indicate that underplating of basaltic magmas can provide the heat required for large scale melting of amphibolitic lower crust provided that ambient wallrock temperatures exceed 800 c based on lithologic and geochemical similarities this model may be applicable to other cordilleran batholiths

rethinking the emplacement and evolution of zoned plutons geochronologic evidence for incremental assembly of the tuolumne intrusive suite california new u pb geochronologic data indicate that the tuolumne intrusive suite california was assembled over a period of at least 10 m y between 95 and 85 ma and that the half dome granodiorite intruded over a period approaching 4 m y simple thermal considerations preclude the possibility that a magma chamber the size of the half dome pluton could have existed as a liquid at shallow crustal depths for that long rather field evidence for sheeting along the margins of the suite the range of ages and the regular decrease of ages toward the center of the suite and within individual plutons suggest incremental assembly geochronologic evidence for incremental assembly is consistent with the failure of geophysical methods to detect large magma chambers with more than 20 melt even in active volcanic areas because it is unlikely that the individual plutons composing the tuolumne ever coexisted as liquid rich magmas the chemical evolution of the suite cannot be the result of simple fractionation and or mixing between exposed units but instead must reflect processes occurring during magma generation

porphyry cu au mineralization in the mirkuh ali mirza magmatic complex nw iran abstract the mirkuh ali mirza cu au porphyry system in east azerbaijan province is located on the western part of the cenozoic alborz azerbaijan volcanic belt the belt is also an important cu mo au metallogenic province in northwestern iran the exposed rocks in the study area consist of a volcaniclastic sequence subvolcanic rocks and intermediate to mafic lava flows of neogene age the volcanic rocks show a typical subduction related magmatic arc geological and geochemical signature with low concentration of nb ta and ti mineralization is hosted by neogene dacitic tuff and porphyritic dacite situated at the intersections of northeast and northwest faults field observations alteration zonation geochemical haloes and isotopic data of the mirkuh ali mirza magmatic complex show similarities with typical convergent margin cu au porphyry type deposits the following features confirm the classic model for cu au porphyry systems a close spatial association with high k calcalkaline to shoshonitic rock related to post collision extensional setting b low grade cu 0 57 c stockworks as well as disseminated sulfides c zonality of the alteration patterns from intense phyllic at the center to outward weak phyllic argillic and propylitic d the presence of a pyritic halo e accompanied by sheeted veins and low sulfidation epithermal gold f mineralization spatially associated with intersection of structures g genetically related to diorite porphyry stocks at depth h geochemical zonation of cu au ag bi cu mo bi au pb zn as au mo pb zn as ag sb mn ba pb zn hg hg from center to outwards i the range of sulfur isotopic values is approximately zero interpreted to have magmatic source and similar to other subduction related porphyry cu deposits