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

assessment of heavy metals concentrations with emphasis on arsenic in the tabriz plain aquifers iran the tabriz area is one of the most industrialized areas in northwest of iran the heavy industrialization and the increasing urbanization are responsible for the rapidly increasing stress on the groundwater of the area the objective of this study was to evaluate heavy metals such as fe mn al zn as and cr in groundwater and their spatial distribution in tabriz plain aquifer the concentrations of fe cr mn as and al in some of the groundwater samples exceed the maximum admissible concentration mac correlation matrix cm and principal components analysis pca methods were employed to identify source apportionment of contamination parameters in groundwater there are two types of aquifers with different quality of water in the plain an unconfined aquifer with saline water and a confined aquifer with fresh water quality arsenic concentrations in the unconfined aquifer and in the recharge areas of the plain boundary are low with an average of 25 8 g l while in the confined aquifer and deep wells the concentrations are high with an average of 122 5 g l the arsenic occurring in groundwater resources of the area originates from geological formations such as alluvial tuffs of sahand mountain and its concentration is highly dependent on hydrogeological and environmental reducing conditions residence time of water and depth of the sampling wells

stratigraphic evidence of human disturbance in an estuary abstract prior to european settlement oligohaline and mesohaline sections of chesapeake bay draining piedmont saprolite supported diverse and abundant diatom and macrophyte populations compositional changes in diatoms and macrophytes in oligohaline sections correspond with 17th and 19th century deforestation and increased siltation while effects on downstream populations were less notable after deforestation previously sparse diatom populations in a mesohaline estuary draining sandy coastal plain soils became more abundant fertilization of cultivated land was accompanied by increased production of both attached and free floating diatoms after the discharge of sewage diatom populations increased enormously in the affected areas followed by a dramatic decrease the decrease suggests silica limitation after intense phosphorus enrichment the loss of macrophytes and increase in planktonic diatoms in oligohaline areas in recent years resemble the historical sequences observed in lakes undergoing eutrophication however in the estuary similar declines have also occurred in macrophyte populations in mesohaline areas where eutrophication is much less severe but where chlorine and herbicide toxicity during the past 20 yr is similar to upstream areas

compositions of biotite amphibole apatite and silicate melt inclusions from the tongchang mine dexing porphyry deposit se china implications for the behavior of halogens in mineralized porphyry systems abstract the dexing deposit located in the circum pacific ore belt is the largest porphyry copper deposit in eastern china it is composed of 3 separate plutons which host three mines tongchang fujiawu and zhushahong mines the porphyritic granodiorite samples studied in this investigation were collected from the tongchang ore forming pluton of this giant deposit this paper presents electron microprobe analyses of biotite apatite amphibole plagioclase potassium feldspar and rehomogenized glassy melt inclusions from the tongchang porphyritic granodiorites petrographic observations of the samples are consistent with portions of the granodioritic magma represented by our samples being overprinted by potassic hydrothermal fluid which variably altered these minerals all of the studied micas are mg rich biotites the biotites are separated into altered magmatic and secondary types based on their petrographic and geochemical characteristics the phlogopite components of the secondary biotites are typically higher than those of the altered magmatic biotites and the x mg values of all biotites correlate negatively with cl contents consistent with the mg cl avoidance principle the x mg values also correlate negatively with k 2 o na 2 o bao feo and tio 2 for both generations of biotites the calculated log f h 2 o f hcl values for 690 k of the coexisting potassic fluids which are determined from the altered magmatic biotite compositions range from 4 43 to 4 67 and are very similar to those of other major porphyry deposits however the log f h 2 o f hf and log f hf f hcl values for the same batch of hydrothermal fluids are significant higher and lower than those of these other porphyry deposits respectively the cl concentrations of amphiboles and melt inclusions range from 0 18 to 0 32 wt and 0 15 to 0 44 wt respectively most apatites trapped in biotite and plagioclase phenocrysts display a bimodal cl distribution 0 19 to 1 35 wt and 1 48 to 3 73 wt similarly the s contents of the apatite also show a distinct bimodal distribution reflecting the effects of variable anhydrite saturation during evolution of the tongchang melt and variable dissolution of anhydrite by saline aqueous fluids the cl contents of the apatites from the tongchang system are typically higher than those of other studied porphyry deposits furthermore the cl contents of the melt inclusions are at or very near the cl saturation levels 0 36 to 0 46 wt at 850 c and 50 mpa and 0 42 to 0 54 wt at 850 c and 200 mpa for these melt compositions at shallow crustal pressures these findings suggest that the area of the granodioritic magma represented by our samples and perhaps the bulk of the tongchang granodioritic magma was rich in cl the melt inclusion compositions are consistent with a high salinity hydrosaline liquid being exsolved directly from the granodioritic melt directly this high salinity hydrosaline liquid was likely very efficient at dissolving transporting and precipitating ore metals in the mineralizing magmatic hydrothermal system

petrogenesis and tectonic significance of late jurassic early cretaceous volcanic intrusive complex in the tianhuashan basin south china abstract the late mesozoic geological framework of south china is characterized by voluminous volcanic rocks and their intrusive counterparts however the ages petrogenesis and tectonic implications of the late mesozoic magmatism in south china especially those in the qinhang zone are poorly constrained the tianhuashan basin is one of the important volcanic basins along the southern margin of the qinhang zone and is mainly composed of the daguding and ehuling formations and their intrusive counterparts laser ablation inductively coupled plasma mass spectrometry la icpms u pb zircon data presented here in conjunction with our previously published data suggest that there are two distinct pulses of magmatism within the tianhuashan basin the granite porphyry was emplaced at 158 157 ma whereas large scale volcanic intrusive rocks were formed at 144 137 ma rather than in the late jurassic as previously regarded the tianhuashan volcanic intrusive rocks have similar whole rock element geochemical and sr nd and zircon hf isotopic compositions suggesting that they were probably derived from similar source regions these rocks exhibit clearly negative and variable bulk rock end t values in a range of 12 07 to 8 69 and low zircon ehf t values from 12 25 to 2 31 with paleo and mesoproterozoic two stage model ages for both nd and hf isotopes 1639 1915 ma and 1051 1970 ma respectively suggesting their derivation dominantly through partial melting of ancient crustal materials with involvement of a mantle derived component in variable proportions and followed by differential assimilation of upper crust during magma ascent an extensional setting associated with the roll back of the paleo pacific slab is favored to explain the petrogenesis of the tianhuashan volcanic intrusive complex the ehf t of zircon increases from late jurassic granite porphyry to early cretaceous magmatic rocks suggesting progressive crust mantle interaction in generating the episodic intermediate felsic magma eruption during late mesozoic our results suggest that the continental extension along the qinhang zone was weak during late jurassic and large scale lithospheric extension did not take place until early cretaceous with ongoing development of slab roll back

a study of the hydrogeological environment of the lishan landslide area using resistivity image profiling and borehole data abstract resistivity image profiling rip surveys was used to develop a lithological and hydrogeological model of the subsurface in the southeastern part of lishan landslide area of central taiwan the bedrock consists of slate in the study area based on rip and rock samples collected from boreholes results three electrical strata are recognized colluvium the shear zone composed of shear gouges and shattered slate and the undisturbed slate formation the steep shear zone with resistivity ranging between 100 260 m plays a crucial role in the local hydrogeological environment because it forms a natural barrier which blocks and retains groundwater flowing down the slope groundwater will brim over the barrier when the water level is high thus the inclined groundwater table remains stable from long term monitoring it strongly indicates that the groundwater recharge is greater than that of discharge therefore the shear zone can provide information about the optimum locations for draining the excess groundwater in situ for slope stability consideration the curved basal surface of the colluvium and the weathered slate can also be discerned from the resistivity variations and boreholes data a series of circular patterns may associate with the main slope failure which migrated upwards from the lower slope

metallogenesis in tibetan collisional orogenic belt i mineralization in main collisional orogenic setting metallogenesis of continents is an important research frontier in the present regional metallogeny and its theoretic framework might be built up by deepening the understanding of metallogenesis in the collisional orogenic belt however metallogenesis in the collisional orogenic belt is rather poorly understood in comparison with metallogenesis in the plate tectonic setting the himalayan tibetan orogenic belt which is characterized by the existence of large scale intense and young mineralizations as well as various kinds of large size and weakly reformed deposits is regarded as an ideal field for understanding the ore forming processes in the collisional orogenic belt based on three years systematical work on metallogeny in the tibetan collisional orogenic belt the authors have summarized the main ore forming events and their temporal spatial distribution analyzed four important metallogenic belts and representative deposits as well as their plutonic processes and tectonic control factors and on such a basis set up a metallogenic model in the main collisional orogenic setting the main collisional event lasted about 25 ma from 65 ma to 41 ma resulting in the formation of the principal part of the tibetan plateau orogenic belt characterized by the south tibet foreland thrust belt the gangdese main collisional tectonic magmatic belt and the north tibet fold thrust belt in company with the collisional orogenic event many important magmatic events were developed as evidenced by the existence of the crust derived muscovite granite potassic calc alkaline granite assemblage 66 50 ma the positive e nd granite gabbro assemblage 52 47 ma and the mantle derived basaltic subvolcanics diabase assemblage as well as widespread and thick linzizong volcanics 64 43 ma the development of above magmatic activities suggests that the deep part of tibetan plateau experienced in turn continental collision 65 52 ma breakoff of continental plate 52 42 ma and low angle underthrust of continental plate 40 ma at least four important ore forming events occurred during the main collisional orogenic epoch which included the sn and rare metal event related to crust derived granite forming the tengchong sn and rare metal ore concentration area in east tibetan plateau the copper gold molybdenum event related to crust mantle derived granite forming a cu au ore belt 100 km long in south gangdese the shear zone gold event related to collisional orogeny forming the potential au belt along the yarlung zangbo suture zone and the copper gold event related to crust uplift forming porphyry epithermal transitional type cu au deposits represented by the xiongcun cu au deposit

squaw peak arizona paleoproterozoic precursor to the laramide porphyry copper province re os dating of two molybdenite samples from the squaw peak porphyry copper molybdenum prospect in central arizona returned essentially identical ages of 1 729 7 and 1 738 7 ma therefore the prospect is not a component of the laramide late cretaceous early tertiary porphyry copper province of southwestern north america as previously presumed these paleoproterozoic ages are similar to that of 1 740 15 ma for the i type magnetite series cherry batholith within which the squaw peak porphyry stock and associated mineralization are located squaw peak cannot be more than a few million years younger than volcanogenic massive sulfide vms copper deposits in the nearby jerome district which are part of the yavapai supergroup host to the cherry batholith these volcanic and intrusive rocks and their associated copper mineralization were formed in a juvenile island arc setting and are now part of the yavapai province which was assembled and accreted to the archean nucleus of north america by 1 68 ga the paleoproterozoic age for squaw peak in conjunction with the existence of the slightly older vms deposits shows that the laramide province of southwestern north america first developed its copper metallogenic signature 1 700 m y ago the presence of this paleoproterozoic copper mineralization may be taken as further support for recently proposed metasomatism of the mantle lithosphere during paleoproterozoic subduction as a precursor to formation of at least part of the laramide porphyry copper province similar spatial associations between inferred metal sources in proterozoic mantle lithosphere and lowermost crust relatively minor copper and or molybdenum mineralization in proterozoic magmatic arcs and important post paleozoic porphyry copper and or molybdenum provinces have recently been documented elsewhere particularly in eastern china and could prove to be of more general exploration significance

accounting for the marine reservoir effect in radiocarbon calibration abstract the radiocarbon dating method is supported by highly refined calibration data empirically obtained from environmental archives nevertheless marine calibration remains problematic due to the spatiotemporally variable marine reservoir effect mre the currently accepted curve for radiocarbon calibration in the ocean is a global curve partly derived by numerical modelling from its atmospheric counterpart as such this curve cannot account for the effects of local phenomena strongly correlated with 14c signatures in seawater e g ocean dynamics and continental input although the radiocarbon community has suggested the use of regional calibration curves that would better represent the heterogeneous ocean reservoir a reasonable method for their construction has not yet been proposed we directly address this longstanding issue in radiocarbon research by exploring the output of a model for the temporal evolution of the mre the limitations of this model are inherited by our method and this hinders the use of the regional curves derived here in many regions of the world ocean nevertheless the approach described in this paper remains valid regardless of the chosen model and our preliminary results show that with the future development of accurate and highly resolved models for the mre this method may be a promising alternative to the use of r values in the process of marine calibration

insights into barrier island stability derived from transgressive regressive state changes of parramore island virginia abstract barrier islands and their associated backbarrier ecosystems front much of the u s atlantic and gulf coasts yet threshold conditions associated with their relative stability i e state changes between progradation erosion and landward migration in the face of sea level rise remain poorly understood the barrier islands along virginia s eastern shore are among the largest undeveloped barrier systems in the u s providing an ideal natural laboratory to explore the sensitivity of barrier islands to environmental change details about the developmental history of parramore island one of the longest 12 km and widest 1 0 1 9 km of these islands provide insight into the timescales and processes of barrier island formation and evolution along this mixed energy coast synthesis of new stratigraphic vibra auger and direct push cores geospatial historical maps aerial imagery t sheets lidar and chronologic optically stimulated luminescence radiocarbon analyses reveals that parramore has alternated between periods of landward migration erosion and seaward progradation during the past several thousand years new chronology from backbarrier and barrier island facies reveals that parramore island has existed in some form for nearly 5000 years following a period of rapid overwash driven retrogradation and coinciding with a period of slow relative sea level rise 1 mm yr parramore stabilized 1000 years ago in partial response to pinning by and sediment delivery from erosion of a pleistocene aged antecedent high following pinning parramore built seaward through development of successive progradational beach and dune ridges morphological and historical evidence suggests that these processes were interrupted by inlet formation possibly associated with an interval of enhanced storminess at least three times during this period following inlet closure in the early 1800s island progradation was rapid with parramore island reaching its maximum width ca 150 years ago it has since switched states again undergoing accelerating erosion 12 m yr since 1980 the relative youth of parramore island is in contrast to many east coast barrier islands which generally reached their present positions about 3500 2000 years ago moreover these results demonstrate that the apparent robustness and stability of parramore are ephemeral features of an island that has undergone multiple state changes within the last 1000 years finally they refine current knowledge of the roles of antecedent topography sediment delivery rates storms and sea level rise in barrier island stability and resilience to future climate change

adakitic signature formed by fractional crystallization an interpretation for the neo proterozoic meta plagiogranites of the ne jiangxi ophiolitic melange belt south china article i nfo the low temperature high pressure metamorphic rocks which are exposed as exotic blocks within the serpentinite matrix of the ne jiangxi ophiolitic melange belt consist of enclave bearing and free meta plagiogranites both rock types are characterized by a metamorphic mineral assemblage consisting of ab rich plagioclase quartz clinopyroxene amphibole while rutile titanite and zircon occur as accessories the former primary magmatic mineral parageneses for the meta mafic enclaves and the meta plagiogranites are similar and consist of an rich plagioclase hornblende ilmenite monazite apatite however the ab rich plagioclase abundance of the meta mafic enclave is much lower and the hornblende and accessory mineral abundances are higher compared with those of the meta plagiogranite host rocks meta plagiogranites with mafic enclaves have a chemical composition similar to that of typical adakites with elevated al2o3 15 86 wt mg 53 5 and sr contents 485 ppm and a positive eu anomaly the rare earth element patterns are highly fractionated with la yb nn12 and low y b4 ppm and yb b0 4 ppm the mafic enclave has a basaltic composition with a negative eu anomaly and has ca 10 times higher hree and y concentrations than the plagiogranite host rocks enclave free meta plagiogranites also have high al2o3 16 08 wt na2o 8 88 wt and mg 52 3 values without obvious eu enrichment or depletion the yand yb concentrations 13 and 1 33 ppm respectively are higher than those of the enclave bearing meta plagiogranites and slightly lower than those of the mafic enclave zircon of the enclave bearing meta plagiogranites gives a weighted mean 206 pb 238 u crystallization age of 970 21 ma these meta plagiogranites have low 87

late triassic melting of a thickened crust in southeastern china evidence for flat slab subduction of the paleo pacific plate abstract the dashuang complex in zhejiang province of southeast china is composed of two distinct lithologies syenite in the west and quartz monzonite in the east they record similar zircon u pb ages of 224 3 ma syenite and 226 2 ma and 227 1 ma quartz monzonite respectively but are notably different in petrography magnetic susceptibility whole rock chemistry zircon hf isotope and zircon trace element characteristics the west dashuang syenitic pluton the west body has high modal alkali feldspar high zircon saturation temperatures high whole rock and zircon mree hree ratios low fe mg ti contents and is depleted in ba sr and eu it also has low magnetic susceptibilities belongs to the ilmenite series and is a peraluminous and ferroan granitoid the east dashuang quartz monzonitic pluton the east body has abundant k feldspar megacrysts with hornblende titanite and biotite being the major ferromagnesian minerals in contrast to the west body the east body has lower zircon saturation temperatures lower whole rock and zircon mree hree ratios higher fe mg ti contents and shows no depletion in ba sr or eu the east body has higher magnetite contents high magnetic susceptibilities and belongs to the magnetite series it is a metaluminous and magnesian granitoid of arc affinity zircon hf isotopic data reveal that both bodies were derived from partial melting of paleoproterozoic igneous protoliths in the lower crust but the east body possibly incorporated subducted terrigenous sediments both bodies have higher melting temperatures and pressures than adjacent cretaceous granitoids reflecting their origin in a thickened hotter lower crust the most feasible model to explain their differences is variations in water content during crustal melting resulting in different melting and crystallization behaviors such melting in a triassic thickened crust with variable water involvement followed by cretaceous magmatism in an extensional setting is consistent with the flat slab subduction model proposed for south china the model involves crustal thickening and partial melting with mantle and lower crustal metasomatism during flat slab propagation in the triassic early jurassic and crustal thinning and extension from the mid jurassic to the cretaceous

zircon u pb and hf o isotopes trace the architecture of polymetallic deposits a case study of the jurassic ore forming porphyries in the qin hang metallogenic belt china abstract the qin hang intra continental porphyry skarn cu polymetallic belt qhmb is among the economically important metallogenic belts in south china the significant differences in the size and metal assemblage of the jurassic magmatic hydrothermal ore deposits in this belt remain as an enigma here we employ zircon u pb and hf o isotopes of the tongshanling and baoshan cu pb zn deposits in the central part of the qhmb to investigate the contrasting metallogenic architecture our sims zircon u pb data indicate that the tongshanling and baoshan granodiorite formed at 160 ma these rocks show high mg values and negative zircon e hf t and high 18 o values suggesting that the magmas of the granodiorite porphyries were mainly generated through the anatexis of older crustal components triggered by the input of mantle derived magma the minor content of amphibole phenocrysts low sr y ratios negative eu anomaly and low zircon ce 4 ce 3 ratios indicate that the porphyries are relatively less oxidized with less water content compared with the ore bearing porphyries in the dexing and yuanzhuding porphyry cu deposits in the northern and southern part of the qhmb suggesting that high magmatic water content and oxidation state are important prerequisites for the formation of large size porphyry skarn copper deposits in the qhmb the positive correlation between zircon e hf t values with the cu reserves as well as zircon 18 o values with the cu cu pb zn ratios of the deposits indicate that the magmatic sources exerted a first order control on the volume and metal assemblage of deposits in the qhmb the hf and nd isotope contour maps indicate that the central part of the qhmb has high potential for pb zn dominated magmatic hydrothermal deposits whereas the northern and southern part of the qhmb are prospective for large cu deposits our results have important implications in formulating regional exploration strategies for jurassic porphyry skarn cu pb zn deposits in the qin hang belt

porphyry cu mo au deposits related to melting of thickened mafic lower crust examples from the eastern tethyan metallogenic domain abstract most porphyry cu deposits in the world occur in magmatic arc settings and are formed in association with calc alkaline arc magmas related to subduction of oceanic lithosphere this contribution reviews a number of significant porphyry cu deposits in the eastern tethyan metallogenic domain they widely occur in a variety of non arc settings varying from post late collisional transpressional and extensional environments to intracontinental extensional environments related to orogenic and anorogenic processes their spatial temporal localization is controlled by strike slip faults orogen transverse normal faults lineaments and their intersections in these non arc settings these deposits are dominated by porphyry cu mo deposits with minor porphyry cu au and epithermal au deposits and exhibit a broad similarity with those in magmatic arcs the associated magmas are generally hydrous relatively high fo2 high k calc alkaline and shoshonitic and show geochemical affinity with adakites they are distinguished from arc magmas and or oceanic slab derived adakites by their occurrence as isolated complexes high k2o contents 1 2 8 5 and much wider range of end t values 10 to 3 and positive ehf t values 4 6 to 6 9 these potassic magmas are most likely formed by partial melting of thickened juvenile mafic lower crust or delaminated lower crust but also involving various amounts of asthenospheric mantle components key factors that generate hydrous fertile magmas are most likely crust mantle interaction processes at the base of thickened lower crust in non arc settings rather than oceanic slab dehydration as in arc settings breakdown of amphibole in thickened lower crust e g amphibole eclogite and garnet amphibolite during melting is considered to release fluids into the fertile magmas leading to an elevated oxidation state and higher h2o content necessary for development of porphyry cu mo au systems copper and au in hydrous magmas are likely derived from mantle derived components and or melts which either previously underplated and infiltrated at the base of the thickened lower crust or were input into the primitive magmas by melt mantle interaction in contrast mo and part of the s in the fertile magmas are probably supplied by old crust during melting and subsequent ascent

geology geochemistry and tectonic settings of the molybdenum deposits in south china a review abstract south china block scb is the area including the yangtze craton and the huanan orogen where scattered precambrian terranes are usually regarded as segments of cathaysia land it is the third most important molybdenum metallogenic province in china next to the qinling dabie area and northeast china containing 29 mo only or mo dominated 9 w mo sn bi and 8 cu mo deposits these 46 deposits are located mainly in 1 the lower yangtze river belt of the northeastern yangtze craton 2 the northern jiangnan orogenic belt that is generally considered a meso neoproterozoic magmatic arc complex accreted onto the southeastern margin of the yangtze craton 3 the wuyi yunkai orogenic belt characterized by local exposures of proterozoic metamorphic terranes and the more widespread sinian uppermost proterozoic to triassic sedimentary sequences and 4 the southeast coastal volcanic belt characterized by yanshanian andesitic to felsic volcanic rocks their genetic types are dominated by porphyry and skarn mineral systems with only a few quartz vein systems the orebodies form veins lens cylindrical shapes pipes or irregular in shape usually controlled by faults at various scales and volcanic subvolcanic complexes the host rocks are variable in lithologies including granites porphyries volcanic breccias and tuffs clastic sediments and carbonate rocks but the high grade orebodies are usually hosted in carbonate shale sequences hydrothermal mineralization processes can be generally divided into four stages from early to late they are 1 k feldspar quartz veins or veinlets 2 quartz molybdenite stockworks 3 quartz polymetallic sulfide stockworks and 4 quartz carbonate fluorite veinlets fluid rock interaction as exemplified by wallrock alteration evolved from k silicate alteration k feldspar quartz mica through phyllic quartz sericite chlorite epidote to propylitic or argillic alteration with skarn alteration typically occurring in skarn type mineral systems hydrothermal mineral assemblages vary between two end members namely the dry system formed by co2 rich fluids and marked by quartz k feldspar fluorite carbonate and epidote and the wet system mainly originated from co2 poor fluids and composed of biotite sericite and chlorite the ore forming fluids are magmatic in origin and show high temperature and high salinity the melt fluid systems forming cu mo deposits are more oxidizing than those forming the w mo or mo deposits as suggested by accessory minerals in granitoids and daughter minerals in fluid inclusions the cu mo deposits are related to the i type granitic rocks adakite like whereas the w mo and mo only systems are related to granitic rocks of s or a types although all of them show high k contents available isotope ages show that the mo and mo bearing deposits were predominantly formed in the early yanshanian orogeny 170 134 ma followed by the late yanshanian orogeny 110 92 ma and the caledonian orogeny 450 410 ma the caledonian mo mineralization has been observed only in the wuyi yunkai orogenic belt and related to the collision between the yangtze craton and the pre devonian huanan orogen or terranes separated from the cathaysia land linked to the assembly of the gondwana supercontinent the early yanshanian mineralization affected the entire huanan orogen and the eastern yangtze craton and resulted from the syn to post collisional tectonism following the closure of eastern paleo tethys the late yanshanian mo deposits mainly occur in the southeast coastal volcanic belt and the southeastern margin of the wuyi yunkai orogenic belt and are related to the westward subduction of the paleo pacific plate the skarn type mineral systems generally show lower re contents than the porphyry type deposits in a same tectonic unit suggesting that carbonate host rocks have lower re contents than the causative porphyries the re contents in molybdenites from porphyry or porphyry skarn cu mo systems are 50 ppm mainly 100 ppm suggesting a source significantly contributed by the mantle whereas the re contents in molybdenites from the mo only or w mo dominated deposits are

marine radiocarbon reservoir corrections r for chesapeake bay and the middle atlantic coast of north america abstract radiocarbon dates from known age pre bomb eastern oyster crassostrea virginica shells provide local marine reservoir corrections r for chesapeake bay and the middle atlantic coastal area of eastern north america these data suggest subregional variability in r ranging from 148 46 14 c yr on the potomac river to 109 38 14 c yr at swan point maryland the r weighted mean for the chesapeake s western shore 129 22 14 c yr is substantially higher than the eastern shore 88 23 14 c yr with outer atlantic coast samples falling between these values 106 46 and 2 46 14 c yr these differences may result from a combination of factors including 14 c depleted freshwater that enters the bay from some if its drainages 14 c depleted seawater that enters the bay at its mouth and or biological carbon recycling we advocate using different subregional r corrections when calibrating 14 c dates on aquatic specimens from the chesapeake bay and coastal middle atlantic region of north america

climatic variability in the eastern united states over the past millennium from chesapeake bay sediments salinity oscillations caused by multidecadal climatic variability had major impacts on the chesapeake bay estuarine ecosystem during the past 1000 yr microfossils from sediments dated by radiometry 14 c 137 cs 210 pb and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10 15 ppt during periods of extreme drought low fresh water discharge and wet climate high discharge during the past 500 yr 14 wet dry cycles occurred including sixteenth and early seventeenth century megadroughts that exceeded twentieth century droughts in their severity these droughts correspond to extremely dry climate also recorded in north american tree ring records and by early colonists wet periods occurred every 60 70 yr began abruptly lasted 20 yr and had mean annual rainfall 25 30 and fresh water discharge 40 50 greater than during droughts a shift toward wetter regional climate occurred in the early nineteenth century lowering salinity and compounding the effects of agricultural land clearance on bay ecosystems

subduction of the nazca ridge and the inca plateau insights into the formation of ore deposits in peru a large number of ore deposits that formed in the peruvian andes during the miocene 15 5 ma are related to the subduction of the nazea plate beneath the south american plate here we show that the spatial and temporal distribution of these deposits correspond with the arrival of relatively buoyant topographic anomalies namely the nazca ridge in central peru and the now consumed inca plateau in northern peru at the subduction zone plate reconstruction shows a rapid metallogenic response to the arrival of the topographic anomalies at the subduction trench this is indicated by clusters of ore deposits situated within the proximity of the laterally migrating zones of ridge subduction it is accordingly suggested that tectonic changes associated with impingement of the aseismic ridge into the subduction zone may trigger the formation of ore deposits in metallogenically fertile suprasubduction environments c 2005 elsevier b v all rights reserved

evidence for temporal fluctuations in marine radiocarbon reservoir ages in the santa barbara channel southern california abstract differences in the 14 c ages of closely associated marine shell and carbonized plant material from stratified archaeological deposits on san miguel island california suggest holocene 10 000 present fluctuations in marine 14 c reservoir ages these fluctuations coincide with 18 o and 13 c shifts measured in mytilus californianus shells from the same stratigraphic contexts and general atmospheric oceanic circulation models for the region based on these data we make three primary observations 1 significant changes appear to have occurred in the radiocarbon reservoir during the holocene 2 these fluctuations appear to correlate with regional oceanographic changes and 3 high resolution 14 c dating of marine shells may require different r values for different periods of time

comparisons of 210pb and pollen methods for determining rates of estuarine sediment accumulation abstract comparisons of sedimentation rates obtained by 210 pb and pollen analyses of 1 m cores collected throughout the potomac estuary show good agreement in the majority of cores that can be analyzed by both methods most of the discrepancy between the methods can be explained by the analytical precision of the 210 pb method and by the exactness with which time horizons can be identified and dated for the pollen method x radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and or mixing of sediments differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods i e 210 pb trends and or possible horizon assignments both methods show the same relative rates with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth the results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures preferably by x radiography to evaluate the extent of mixing of the sediments time horizons whether paleontologic or isotopic are generally blurred where mixing has occurred precluding precise identification whenever possible two methods should be used for dating sediments because a rate albeit erroneous can be obtained isotopically in sediments that are mixed accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon where the historical record does not provide a precise date for the pollen horizon or where scouring has removed some of the sediment above a dated pollen horizon

shrimp zircon u pb geochronological and whole rock geochemical evidence for an early neoproterozoic sibaoan magmatic arc along the southeastern margin of the yangtze block abstract it has been generally accepted that the south china block was formed through amalgamation of the yangtze and cathaysia blocks during the proterozoic sibaoan orogenesis but the timing and kinematics of the sibao orogeny are still not well constrained we report here shrimp u pb zircon geochronological and geochemical data for the taohong and xiqiu tonalite granodiorite stocks from northeastern zhejiang southeastern margin of the yangtze block our data demonstrate that these rocks dated at 913 15 ma and 905 14 ma are typical amphibole rich calc alkaline granitoids formed in an active continental margin combined with previously reported isotopic dates for the 1 0 ga ophiolites and 0 97 ga adakitic rocks from northeastern jiangxi the timing of the sibao orogenesis is thus believed to be between 1 0 and 0 9 ga in its eastern segment it is noted that the sibao orogeny in south china is in general contemporaneous with some other early neoproterozoic 1 0 0 9 ga orogenic belts such as the eastern ghats belt of india and the rayner province in east antarctica indicating that the assembly of rodinia was not finally completed until 0 9 ga

magmatism along the southeast margin of the yangtze block precambrian collision of the yangtze and cathysia blocks of china the time and the environment of formation of igneous rocks along the southern margin of the yangtze continental block in southern anhui province and northeastern jiangxi province china are discussed sm nd dating for samples from two ophiolite suites give ages of about 1 ga late proterozoic granodiorites in the study area have ages of about 0 9 ga and have normal intrusive relations against banxi group metamorphic country rocks trace element abundances and initial nd isotope ratios for ophiolite and proterozoic granodiorites are consistent with formation in an island arc environment in contrast sr and nd isotopes for mesozoic granitoids of the region suggest that they are products of remelting of crustal sources similar to the basement of the yangtze block these relations do not support a recently proposed mesozoic overthrust tectonic model for southeast china but rather favor a late precambrian collision history for the yangtze and cathysia blocks

geological history of chesapeake bay usa abstract chesapeake bay began to form as a partially enclosed coastal water body separated from the open ocean in the late pliocene and developed through the pleistocene and into the holocene in response to coastal marine processes and major cycles of sea level rise and fall during times of emergence and low sea level the rivers excavated channels in the broad coastal plain and subaerial processes eroded and modified existing landforms during periods of high sea level the delmarva peninsula lengthened as a major barrier spit progressively enclosing what was to become chesapeake bay and nearshore deposits of sediment accumulated along the western shore enlarging the inter river peninsulas highstands of sea level also resulted in the carving of regional scarps that mark the maximum shorelines as the sea cycled back and forth across the coastal plain and continental shelf a series of thin strata were deposited then modified the bay as it exists today may be at an end stage in the progression as the bay mouth has begun to function as a tidal inlet

porphyry cu deposits in collisional orogen setting a preliminary genetic model porphyry cu deposits pcds as the primary source of copper are usually thought to be formed in a magmatic arc setting they can also occur in collisional orogen or intraplate settings the classic pcds model proposed by lowell and guilbert 1970 has been widely accepted by economic geologists because of its practical value in the exploration of pcds in the arc setting especially in the circum pacific belt however lowell and guilbert s model fails to give a reasonable explanation of the pcds in the collisional orogen setting the authors therefore give a detailed description of geological setting tectonic control magma source general characteristics of the ore deposit source and enrichment mechanism of metals fluid source and evolutionary path of pcds in the qinghai tibetan collisional orogen setting and propose a preliminary genetic model several points are emphasized in this model mineralization related porphyry intrusions in the collisional orogen setting are geochemically adakitic rocks which originaue from the newly formed lower crust and are triggered by the upwelling of asthenosphere and or the transition of structure mechanism from extrusion to extension the enrichment of cu and other metals in the adakitic magmas results from the relatively high oxidation state of the source in which the bulk of the sulfur is dissolved in the sulfate form with the result that sulfide compatible elements such as cu and au can also behave as incompatible elements and will be retained in the evolving magmas the ascent of the adakitic magmas is usually constrained by large sized strike slip fault systems triggered by oblique collision or by large sized normal faults induced by lithosphere removal whereas the emplacement of the adakitc magmas is generally controlled by mine scale structures the magma chamber usually exists below large sized and especially giant deposits in these deposits cu s and magmatic fluids which are essential for the formation of porphyry cu deposits generally originate directly from the magma chamber the deposits reinforce most of the generalized characteristics of porphyry cu deposits in continental arc settings except for the fact that they show relatively strong k silicate alteration due to high k h value in the high k adakitic magma dominated ore forming fluid sulfide precipitation mainly occurs during k silicate alteration usually in response to the change of temperature pressure salinity f o2 and ph value especially to the change of temperature and pressure

anthropogenically induced changes in sediment and biogenic silica fluxes in chesapeake bay sediment cores as long as 20 m dated by 1 4 c 2 1 0 pb and 1 3 7 cs methods and pollen stratigraphy provide a history of diatom productivity and sediment accumulation rates in chesapeake bay we calculated the flux of biogenic silica and total sediment for the past 1500 yr for two high sedimentation rate sites in the mesohaline section of the bay the data show that biogenic silica flux to sediments an index of diatom productivity in the bay as well as its variability were relatively low before european settlement of the chesapeake bay watershed in the succeeding 300 400 yr the flux of biogenic silica has increased by a factor of 4 to 5 biogenic silica fluxes still appear to be increasing despite recent nutrient reduction efforts the increase in diatom produced biogenic silica has been partly masked in concentration terms by a similar increase in total sediment flux this history suggests the magnitude of anthropogenic disturbance of the estuary and indicates that significant changes had occurred long before the twentieth century

geochronology geochemistry and sr nd hf s pb isotopes of the early cretaceous taoxihu sn deposit and related granitoids se china abstract the taoxihu deposit eastern guangdong se china is a newly discovered sn polymetallic deposit zircon u pb dating yielded 141 8 1 0 ma for the sn bearing granite porphyry and 145 5 1 6 ma for the biotite granite batholith it intruded the age of the granite porphyry is consistent within error with the molybdenite re os isochron age 139 0 1 1 ma of the sn mineralization indicating a temporal link between the two geochemical data show that the granite porphyry is weakly peraluminous contain high si na and k low fe mg ca and p and relatively high rb sr and low k rb values the rocks are enriched in rb th u k and pb and depleted in ba sr ti and eu resembling highly fractionated i type granites they contain bulk rock initial 87 sr 87 sr of 0 707371 0 707730 and end t of 5 17 to 4 67 and zircon ehf t values from 6 67 to 2 32 with late mesoproterozoic t dm2 ages for both nd and hf isotopes this suggests that the granite porphyry was likely formed by the partial melting of the crustal basement of mesoproterozoic overall residence age with minor mantle input 34 s cdt values of the taoxihu chalcopyrite and pyrite range from 0 1 to 2 1 average 0 9 implying a dominantly magmatic sulfur source the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios of the taoxihu sulfide ores are 18 497 18 669 15 642 15 673 and 38 764 38 934 respectively indicating a mainly upper continental crustal lead source with minor mantle contribution the highly fractionated and reduced low calculated zircon ce 4 ce 3 and eu n eu n values nature of the ore forming granitic magma may have facilitated the sn enrichment and played a key role in the sn mineralization we propose that the ore forming fluids at taoxihu were of magmatic hydrothermal origin derived from the granite porphyry and that both the granite porphyry and the sn mineralization were likely formed in an extensional setting possibly related to the subduction slab rollback of the paleo pacific plate

stability in the south pacific surface marine 14c reservoir over the last 750 years evidence from american samoa the southern cook islands and the marquesas abstract although minor climatic and sea level changes have been documented for the south pacific during the late holocene our understanding of the consequent impact of these changes on the marine 14 c reservoir and therefore the 14 c content of shellfish is limited ultimately this has implications for documenting the chronology of human movement and adaptation in this region in this paper we compare marine reservoir r data obtained from tightly controlled archaeological proveniences with known age pre ad 1950 shells from the southern cook islands american samoa and marquesas islands results indicate that there has been no significant change in the near shore marine reservoir in these three locations over the last ca 750 years furthermore known age pre ad 1950 shell samples provide more precise r values for use in sample calibration than archaeological paired shell charcoal samples this is attributed in part to the limitations of assigning provenance and age to material from archaeological sites on the basis of these results we conclude that the known age pre ad 1950 shell derived r values can be used to calibrate shell 14 c results from deposits of late holocene age

mesozoic large scale magmatism and mineralization in south china preface abstract south china is famous for its polymetallic deposits with more than 50 of the world s w and sb reserves and 20 of the sn reserves as well as abundant cu mo pb zn au ag ta nb hree and u this special issue reports recent progress on the tectonic evolution magmatism and ore deposits of south china which leads to a more comprehensive understanding of the mesozoic large scale magmatism and mineralization events 1 south china has been located in backarc settings during multiple subductions since the paleozoic which may have contributed to pre enrichments of the ore forming materials 2 the pacific plate subduction was a principle factor that controlled the late mesozoic large scale magmatism and mineralization in south china through flat subduction ridge subduction slab tearing and slab rollbacks

implications of a freshwater radiocarbon reservoir correction for the timing of late holocene settlement of the elk hills kern county california abstract uncertainties regarding the magnitude of freshwater radiocarbon reservoir effects can introduce random errors into dates on archaeological freshwater carbonates as a result many archaeologists avoid dating freshwater shells unless no other datable materials are available the chronology of prehistoric occupation of the former naval petroleum reserve no 1 npr 1 at elk hills kern county has been established with 50 radiocarbon dates on freshwater mussels gonidea and anodonta sp characterization of any freshwater radiocarbon reservoir effect is crucial for the accurate interpretation of inferred settlement and subsistence changes on the elk hills paired charcoal and freshwater mussels sampled from closely associated contexts were dated to identify a freshwater reservoir effect paired anodonta and gonidea sp shells were dated to investigate interspecific differences in fractionation results indicate that a 340 20 14 c yr correction should be applied to conventional 14 c dates on freshwater carbonates in the buena vista basin before calendar calibration evidence of interspecific differences is inconclusive dates recalibrated with the reservoir correction indicate that widespread occupation of the elk hills is correlated with increasing precipitation towards the end of the medieval climatic anomaly and during the little ice age suggesting that slough resource exploitation may have been driven by regional population pressure rather than drought related declines in aquatic productivity

geochronology and petrogenesis of the qibaoshan cu polymetallic deposit northeastern hunan province implications for the metal source and metallogenic evolution of the intracontinental qinhang cu polymetallic belt south china abstract the recently recognized qinhang metallogenic belt qhmb is an economically important intracontinental mesozoic porphyry skarn cu polymetallic metallogenic belt in south china however the origin of the ore bearing magma and the major factors controlling the different metal assemblages in the qhmb are still unclear the qibaoshan deposit is a large cu au pb zn ag fe deposit located at the juncture between the northern and central parts of the qhmb in this study new zircon u pb ages hf o isotopic data molybdenite re os ages and whole rock geochemical data are combined to constrain the timing of the mineralization and the origin and petrogenesis of the ore bearing porphyry in the qibaoshan deposit the ages obtained from both zircon u pb and molybdenite re os dating fall in the late jurassic between 152 7 and 148 3 ma revealing that this deposit is significantly younger than previously estimated 227 184 ma the qibaoshan ore bearing quartz porphyry shows variable negative zircon ehf t values 14 8 to 5 5 high 18o values 8 4 to 10 8 and high mg values 69 1 to 73 0 indicating that it formed via the partial melting of ancient crust triggered by the injection of mantle derived magma zircon hf o isotopic modeling of the mixing of two extreme endmembers indicates that the magmatic source comprised 70 80 reworked ancient crustal components and 20 30 depleted mantle components based on comparisons with other ore bearing porphyries in the qhmb a magmatic source dominated by crust derived material and relatively low oxygen fugacities fmq 1 8 to fmq 0 8 was responsible for the high pb zn cu ratio in the qibaoshan deposit and the pb zn and ag were mainly derived from the reworked ancient crust although four analyses of inherited neoproterozoic zircons 800 ma have variable positive ehf t values 0 72 to 11 21 indicating that neoproterozoic juvenile crust was involved in the formation of the qibaoshan ore bearing quartz porphyry the relatively low oxygen fugacities fmq 1 2 to fmq 0 4 of the parent magma of these inherited zircons suggest that this parent magma could not have provided significant metallic cu for mineralization in the qibaoshan cu polymetallic deposit therefore the metallic cu in the qibaoshan cu polymetallic deposit was probably provided by the injection of the mantle derived magma because ore forming magmas with relatively low oxygen fugacities have low au solubility the large au mineralization in the qibaoshan deposit may be related to high background values of au in this area our data integrated with regional petrogeochemical data indicate that the magmatic source exerted a first order control on the different metal assemblages in the deposits in the qhmb

epithermal deposits in south china geology geochemistry geochronology and tectonic setting abstract south china block scb is the broad area including the yangtze craton in the northwest and huanan orogen in the southeast it is an important epithermal metallogenic province in china containing at least 1 high sulfidation hs and 42 low sulfidation ls au ag cu pb zn sb epithermal deposits porphyry type mineralization was recognized in four of the ls deposits and thus they were regarded as ls p type these 43 deposits are mainly located in 1 the lower yangtze river belt and 2 the northeastern jiangnan orogenic belt in the yangtze craton 3 the wuyi yunkai orogenic belt and 4 the southeast coastal volcanic belt in the huanan orogen they are mostly located in mesozoic volcanic basins especially where the regional faults and their subsidiaries occurred the host rocks include jurassic cretaceous volcanic sedimentary rocks coeval or slightly older subvolcanic granitoids and breccias and metamorphic basement rocks the alteration of the hs epithermal deposit zijinshan cu au zoned from silicic vuggy quartz through alunite to dickite and phyllic alteration zones from the ore veins outwards the alteration of the ls deposits is zoned from adularia chalcedony bladed calcite or quartz pseudomorphs after bladed calcite in ore veins to distal illite sericite chlorite kaolinite assemblages for those ls p systems besides the dominated ls alteration assemblages phyllic and potassium silicate alteration related to porphyry mineralization were identified acid leaching textures and vein stockwork and breccia structures are common in hs deposit while the ls epithermal deposits are characterized by open space filling crustifications colloform banding and comb structures the ore forming fluids are low temperature low salinity meteoric water dominated in most epithermal deposits in scb with variable input of magmatic water the ore components were derived from both the deep magma and host rocks and transported upwards or laterally and precipitated in the fracture systems by fluid boiling mixing and cooling most of the epithermal deposits are formed at depth of

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

radiocarbon age calibration at archaeological sites of coastal massachusetts and vicinity abstract radiocarbon ages of 15 paired marine and terrestrial archaeological samples along with 10 marine samples of known historic age from massachusetts maine connecticut and new york provide data for studying the reservoir effect on these coasts the marine calibration method of stuiver pearson braziunas 1986 proves effective at correcting the ages of shells from boston harbor cape cod and nan ucket island massachusetts and several samples from maine and long island sounc however some shells from long island sound and the lower hudson and merrimack rivers exhibit very large reservoir ages fluvial discharges carrying old terrestrial carbon can explain these large variations although oceanic upwelling cannot be ruled out

cooling and exhumation of the mid jurassic porphyry copper systems in dexing city se china insights from geo and thermochronology the dexing porphyry copper and yinshan polymetallic deposits in dexing city southeastern china are both giant porphyry ore systems located 15 km apart they formed synchronously and share a similar magma source and metallogenic evolution but their metal endowment dominant rock types and alteration assemblages differ significantly in this contribution we investigate the cause of these distinctions through new molybdenite re os ages and zircon and apatite u th he thermochronology data dexing has a molybdenite re os age of 170 3 ma zircon u th he zhe ages of 110 to 120 ma and apatite u th he ahe ages of 7 to 9 ma in contrast yinshan has older zhe ages of 128 to 140 ma and an ahe age of 30 ma viewed in combination with previously published data we conclude that the apparently slow cooling experienced by these bodies is primarily a reflection of their experiencing multiple episodes of thermal disturbance we tentatively infer that both deposits were exposed in the late miocene or more recent time with the dexing deposit more deeply exhumed than yinshan our study has exploration implications for deeper porphyry style ores at yinshan and for porphyry deposits in non arc intraplate settings in general

determination of mechanisms and hydrogeological environments of gangxianlane landslides using geoelectrical and geological data in central taiwan electrical resistivity tomography ert single point resistance logging with time lapse and geological and groundwater level data are utilized to determine the mechanism of and a hydrogeological model of the gangxianlane landslide in the west central part of taiwan the rock surface and geometry of the colluviums were found by integrating ert and borehole data the iso resistivity line in the bedrock broadly followed the bedding plane indicating that the contribution of lithology to resistivity exceeds that of groundwater the results of single point resistance logging with time lapse and borehole data reveal that the bedrock has low permeability which is associated with poorly developed joints and fractures the fine grain content part including the clayey layer almost parallel to the bedding plane of the bedrock and between the colluvium and the bedrock in the upper part of the landslide served as the slip surface and is believed to have been recently produced it can block and retain water in the colluviums accordingly this slip surface has the potential to re slip in the future another slope failure involved rock collapse by a well developed open release joint close to the huoshaoping terrace it is also related to groundwater flow over a large gradient from the huoshaoping terrace it is a key to determining whether this landslide will expand in the future

estuarine processes and their stratigraphic record paleosalinity and sedimentation changes in the hudson estuary north america paleosalinity estimates and rates of sedimentation inferred from core samples from the hudson estuary for the interval between 6 4 and 1 3 ka indicate a possible role for the estuarine turbidity maximum etm in influencing patterns of estuarine sedimentation at centennial to millennial time scales currently in the estuary sedimentation is localized via sediment trapping particularly in the vicinity of the etm 13 26 km upstream from battery park fbp at the southern tip of manhattan in water depths greater than 4 m and on the western side of the estuary data presented in this paper are from cores located within the segment of the estuary 29 50 km fbp age constraints are provided by c 14 dating paleoenvironmental interpretations are based upon paleosalinity estimates grain size variability and sedimentary structures paleosalinity was inferred on the basis of foraminiferal biofacies analysis and a new method for estimating summertime paleosalinity using oxygen isotope measurements in bivalve shell material the isotopic analysis of a narrow size fraction 1 0 1 7 mm representing summer growth of a single bivalve species gemma gemma reduces the uncertainty related to annual changes in temperature data from f45 km fbp indicate a gradual decrease in summertime paleosalinity between 6 4 and 2 0 ka from 25 20x to 15 10x the latter is similar to present day values these results are consistent with the conclusion of an earlier low resolution study sedimentation rates are generally low and are similar to the rate of sea level rise in the hudson river lowest sedimentation rates are noted in short 2 3 to f1 3 ka we hypothesize that the observed pattern in sediment accumulation relates to a location for the etm some 20 km upstream of its present position at 3 ka downstream migration of the etm since 3 ka is ascribed to shoaling of the estuary effectively squeezing the marine saltwater wedge in the same direction and off marginal flats into the channel such shoaling would have enhanced the role of waves in mixing marine and fresher surface water and reduced the effect of the etm in

radiocarbon dating chronologic framework and changes in accumulation rates of holocene estuarine sediments from chesapeake bay abstract rapidly accumulating holocene sediments in estuaries commonly are difficult to sample and date in chesapeake bay we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of holocene sediment accumulation in the bay carbon in these sediments is a complex mixture of materials from a variety of sources analyses of different components of the sediments show that total organic carbon ages are largely unreliable because much of the carbon including coal has been transported to the bay from upstream sources and is older than sediments in which it was deposited mollusk shells clams oysters and foraminifera appear to give reliable results although reworking and burrowing are potential problems analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower chesapeake bay the biogenic carbonate radiocarbon ages are compatible with 210pb and 137cs data and pollen stratigraphy from the same sites post settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries including the chesapeake our data show that large variations in sediment mass accumulation rates occur among sites at shallow water sites local factors seem to control changes in accumulation rates with time our two relatively deep water sites in the axial channel of the bay have different long term average accumulation rates but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay mass accumulation rates at the two deep water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the chesapeake watershed

patterns of recent sediment accumulation in chesapeake bay virginia maryland u s a tributaries abstract sediment accumulation rates obtained from 39 cores in 10 tributaries of the western shore of chesapeake bay average 0 30 cm yr 1 since european settlement compared with pre settlement rates in three tributaries of 0 14 cm yr 1 drainage areas of six of the tributaries extend from the coastal plain into the piedmont and four are restricted to the coastal plain rates are highly variable but higher in the upper parts of the tributaries and lower at the mouths during the period of early agriculture when pre settlement rates are based on unpublished reports of 14c dates ranging from 670 to 5330 yr b p of peat layers from three western shore tributaries where sediment deposition is believed to have been continuous post settlement rates are average rates calculated between a maximum of five pollen horizons the pollen horizons represent historically documented changes in the regional vegetation and include initial land clearance 1634 1650 1720 and 1730 depending on the tributary shift to intensive agriculture 1780 and 1840 beginning of the chestnut blight 1910 demise of chestnut 1930 and the beginning of large scale urbanization 1960

spatial temporal framework for the closure of the junggar ocean in central asia new sims zircon u pb ages of the ophiolitic melange and collisional igneous rocks in the zhifang area east junggar abstract the closure time of the junggar ocean is one of the hottest topics surrounding the tectonic evolution of the central asian orogenic belt caob this paper reports sims zircon u pb ages of the ophiolitic melange and collisional igneous rocks in the zhifang area east junggar our new results reveal the following evidence 1 the west hill ophiolitic melange in the zhifang area contains segments of the 371 ma morb type layered rocks and 363 ma oceanic islands which were intruded by the 348 ma syn collisional quartz diorites 2 the ophiolitic melange and 348 ma syn collisional quartz diorites are overlain by the 342 ma andesitic tuffs and 3 the 342 ma andesitic tuffs and successive 332 ma granodiorites gabbro were formed at late collisional setting whereas the 314 ma granitic porphyry at post collisional setting we suggest that the junggar ocean in the zhifang area was opened before 371 ma and 363 ma and possibly closed before 348 ma by combining the published u pb ages of the mayile tangbale darbute kalamaili zhifang daheishan mtdkzd ophiolite belt early carboniferous volcanic rocks unconformably overlying the mtdkzd ophiolite belt bimodal volcanic rocks and granitoids within and adjacent to the mtdkzd ophiolite belt it is suggested that the junggar ocean was possibly opened scissors like from the neoproterozoic ordovician mayile tangbale ocean eastwards through the silurian devonian darbute karamay ocean finally to the devonian early carboniferous kalamaili zhifang ocean and closed scissors like from the zhifang kalamaili area in the eastern segment westwards to the darbute karamay area in the western segment tectonic collage between the yemaquan xiemisitai arc and junggar block occurred at approximately 343 348 ma the junggar orogenic belt went through late collisional stage at 343 330 ma post collisional period after 330 ma and post collisional extensional regime after 320 ma with an intensive stage at around 303 ma

application of electrical resistivity tomography technique for investigation of landslides a case from turkey electrical resistivity imaging is a widely used tool in near surface geophysical surveys for investigation of various geological environmental and engineering problems including landslide in this study an electrical resistivity tomography ert survey was conducted in a landslide area located in the soke district of aydin turkey in 2003 the neogene aged units on the slope next to a newly built school building became unstable due to an excavation work and moved after a heavy rainfall the resulting landslide partly covered the school the authors carried out a 2 d resistivity survey along three profiles over the landslide mass using a wenner configuration it yielded useful information about the geometry and characteristics of the landslide in addition a 2 d synthetic resistivity modelling study was carried out to understand the response of the resistivity method to a landslide problem before the field surveys eight boreholes were also drilled in the landslide area both the drilling and resistivity results indicated the presence of a fault in the site also the resistivity data from the line measured along the axis of the landslide revealed the surface of rupture

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

sea level changes and geoarchaeology between the bay of capo malfatano and piscinni bay sw sardinia in the last 4 kys abstract the bay of malfatano cape is the berthing home to one of the most important maritime structures from the punic roman times in the mediterranean two opposing monumental structures have been preserved between 7 and 2 m due to rising sea level recent studies have identified the paleo sea level relating the eustatic component to the glacio hydroisostatic deformations this paper through stratigraphic palaeontological and geochronological data aims to trace the bay of capo malfatano s evolution in relation to the sea level rise during the last 4 kys based on data derived from geophysical surveys paleoshore lines have been redrawn and compared with data derived from coring in the inner part of the creek finally we evaluated the relationship between changes in palaeogeography and human settlements from the bronze age the breakwaters have been surveyed in detail using d gps techniques correlated to the geodesic 0 level through this data the shape of the breakwaters has been reconsidered and consequently the palaeo sea level has been re evaluated

sulfides associated with podiform bodies of chromite at tsangli eretria greece small bodies of pyrrhotite chalcopyrite minor pentlandite and magnetite occur at the peripheries of podiform bodies of chromite in ultramafic ophiolitic rocks at tsangli eretria central greece banding of magnetite and sulfide within the bodies is reminiscent of magmatic banding a magmatic origin has been proposed for similar sulfide masses in the troodos ophiolite panayiotou 1980 the compositions of the host rocks chromite and of the sulfides have been investigated on average the sulfide mineralization recalculated to metal content in 100 sulfide contains 0 55 ni 5 15 cu 0 29 co 9 ppb pd 179 ppb pt 16 ppb rh 112 ppb ru 31 ppb ir 58 ppb os and 212 ppb au these metal contents particularly the high cu cu ni ratio of 0 78 and the pt pd pt ratio of 0 95 are inconsistent with the sulfides having reached equilibrium with their ni rich host rocks at magmatic temperatures and accordingly it is concluded that they are not of magmatic origin the average 34s value of the sulfide bodies is 2 while that of a sample of pyrite from country rock schist is 15 6 these values are inconclusive as to the origin of the sulfur it is suggested that the sulfides have been precipitated by hydrothermal fluids possibly those responsible for the serpentinization of the host rocks the source of the metals may have been the host rocks themselves

petrogenesis of adakitic porphyries in an extensional tectonic setting dexing south china implications for the genesis of porphyry copper mineralization the dexing adakitic porphyries quartz diorite granodiorite porphyries associated with giant porphyry cu deposits are located in the interior of a continent south china they exhibit relatively high mgo cr ni and sr contents high la yb and sr y ratios but low yb and y contents similar to adakites produced by slab melting associated with subduction however they are characterized by bulk earth like nd sr isotope compositions end t 1 14 to 1 80 and 87 sr 86 sr i 0 7044 0 7047 and high th 12 6 27 2ppm contents and th ce 0 19 0 94 ratios which are different from those of cenozoic slab derived adakites sensitive high resolution ion microprobe shrimp geochronology studies of zircons reveal that the dexing adakitic porphyries have a crystallization age of 171 3ma this age is contemporaneous with middle jurassic extension within the shi han rift zone and within plate magmatism elsewhere in south china indicating that the dexing adakitic porphyries were probably formed in an extensional tectonic regime in the interior of the continent rather than in an arc setting their high th contents and th ce ratios and middle jurassic age argue against an origin from a neoproterozoic 1000ma stalled slab in the mantle taking into account available data for the regional metamorphic magmatic rocks and the present day crustal thickness 31km in the area we suggest that the dexing adakitic porphyries were most probably generated by partial melting of delaminated lower crust which was possibly triggered by upwelling of the asthenospheric mantle due to the activity of the shi hang rift zone moreover the dexing adakitic magmas must have interacted with the surrounding mantle peridotite during their ascent which elevated not only their mgo cr and ni contents but also the oxygen fugacity fo2 of the mantle the high fo2 could have induced oxidation of metallic sulfides in the mantle and mobilization of chalcophile elements which are required to produce associated cu mineralization therefore the cu metallogenesis associated with the dexing adakitic porphyries is probably related to partial melting of delaminated lower crust similar to the metallogenesis accompanying slab melting

groundwater flow after heavy rain in landslide slope area from 2 d inversion of resistivity monitoring data in the interest of monitoring the flow of groundwater from heavy rains we conducted surface resistivity tomography through the vadose zone over several days the measured data were modeled by 2 d inversion a laboratory experiment was carried out to estimate the difference in geological characteristics we measured the effects of groundwater fluctuation using two tank models one using sand and one using bricks which represent unconsolidated sediments and jointed rocks respectively in the sand model we succeeded in monitoring water level fluctuation as the change in resistivity over time in the brick model the water level did not appear as a distinct boundary field experiments were carried out in an area in which the near surface conditions consisted of heavily weathered rocks with an extensive shear zone several tens of meters thick measurements were performed over 42 days during which we observed changes in resistivity associated with heavy rainfall it became clear that resistivity decreases of up to 8 were present in highly porous zones in heavily weathered layers this result suggests a connection between a decrease in resistivity and the infiltration of rainwater in particular a pronounced zone of minimum resistivity may indicate infiltration of rainwater into the vadose zone the relationship between resistivity changes and rainfall was inferred to depend on the permeability of geological structure

resistivity and induced polarization surveys for slope instability studies in the swiss alps a geoelectrical investigation has been carried out in the swiss alps near the dent de nendaz within the southern part of the rhone valley in the swiss alps to delineate groundwater circulation within an unstable slope this unstable zone is characterized by a landslide area with clear scarps and hummocky ground at the bottom of the slope large scale apparent resistivity mapping provided information on the main pathways for water transport within the slope subsequently 2d resistivity and induced polarization imaging supplied details on the region of instability located at the bottom of the slope polarizable units identified in the region of instability could be linked to a clay rich unit or to local enrichment of graphite within the bedrock our results illustrate how low permeability clay graphite units and permeable water bearing units could be distinguished using a combined interpretation of resistivity and ip data in slope instability studies

well logging methods in groundwater surveys of complicated aquifer systems bohemian cretaceous basin geophysical well logging methods including borehole flow logging can significantly contribute to a detailed understanding of hydrogeological conditions in basins with complicated sedimentary structure in studies undertaken to make optimal use of water sources or to protect those resources from contamination it is a common practice to delineate geological and hydrogeologic conditions at the scale used in geological maps and surface surveys however there is a need for more detailed descriptions of basin structure for many tasks related to water resources management and hydrologic research this paper presents four specific examples of boreholes in complex hydrogeologic settings where useful information was provided by geophysical logging 1 identification of large scale upward cross flow between aquifer horizons in an open borehole 2 confirmation of continuous permeability throughout a long borehole interval 3 identification of leakage into a test well via a defective casing joint 4 evidence for downward flow in open boreholes and 5 identification of permeable beds associated with water inflows during aquifer tests these borehole geophysical measurements provide important information about the detailed lithological profiles of aquifers especially in the absence of core enabling the optimization of groundwater monitoring resource use and wellhead protection activities

reconnaissance geophysical methods in landslide investigations abstract landslides are a natural hazard in many countries and often affect civil engineering structures and projects three aspects in particular require examination in a geotechnical appraisal of a landslide s stability in engineering terms 1 the definition of its three dimensional shape with particular reference to shear surfaces and failure planes 2 the definition of the hydrogeological regime with regard to water input to the landslide and its distribution within the slip mass 3 the detection of movement by or within the slip mass and the characterisation of such movements the site investigation costs may be very high since landslides may be extremely large structurally complex and topographically severe it is therefore advantageous in suitable circumstances to carry out reconnaissance geophysical surveys to define the structure and to guide optimum siting of boreholes and pits and ultimately the installation of piezometers inclinometers etc standard surface geophysical techniques including the seismic electrical resistivity acoustic emission and borehole methods have all been applied with varying success to look at a landslide before a major site investigation commences in recent years electromagnetic methods have been the subject of considerable research in this field and significant advances have been made in this paper the application of the above geophysical methods at the reconnaissance stage in a landslide investigation has been reviewed and illustrated with several case histories taken from different geological settings

radiocarbon dating and the old wood problem the case of the hohokam chronology abstract many archaeological chronologies including that of the hohokam in southern arizona are based on a series of radiocarbon dates on wood this paper argues that because of variability in rates of wood decay processes in the environment and in systemic context such archaeological chronologies are potentially biased towards excessive antiquity by an old wood problem and must be reassessed following the theoretical insights of dean 1978 this paper sets forth principles and procedures for relating radiocarbon dates to cultural events emphasis is placed on identifying and taking into account the formation processes of 1 the dated specimens and 2 the deposits that yielded them this methodological framework is applied to hohokam radiocarbon dates and a chronology much shorter than the original gladwin haury formulation is supported

molybdenum and boron isotopic compositions of porphyry cu mineralization related adakitic rocks in central eastern china new insights into their petrogenesis and crust mantle interaction

the analysis of rainfall induced slope failures at iva valley area of enugu state nigeria this paper analyses the dominant mechanisms of slope failures and identifies potential obstacles to landslide hazard reduction at the iva valley area enugu nigeria the landscape is replete with landslide scars and gullies of varied sizes and the slope deposits comprise unconsolidated friable sands inter bedded with thin units of montmorillonitic claystone forty three landslide events were identified in the study area with most being shallow short run out movements with slip surface depth 2 m the study found the landslides mainly occur in the beginning of rainy season characterized by short duration high intensity rainfall an integrated approach comprising field mapping laboratory tests and numerical analyses reveals that the barren nature of the slopes prior to the outset of rainy season high rainfall intensity erosion overgrazing soil characteristics and the site s unique lithologic sequence are the main causes of instability shearing tests under several conditions showed that the soils strongly strain soften until low steady state strength is achieved a computer code based on this strength reduction technique used input parameters obtained from the field and laboratory studies to simulate a landslide with similar structure travel distance and distribution area it is noted that urbanization has gradually increased the vulnerability of the society s poor to landslide hazards as they now erect unplanned residence tents and blocks on the slopes this work is part of a regional study aimed at finding ways of protecting the vulnerable by generating data that could be used to build future landslide susceptibility map

element redistribution during hydrothermal alteration of rhyolite in an active geothermal system yellowstone drill cores y 7 and y 8 abstract hydrothermal alteration of the 0 54 ma biscuit basin rhyolite flow in yellowstone drill cores y 7 and y 8 has involved significant changes in ti normalized whole rock concentrations of li mg ca na k mn rb sr sb cs ba and u whereas such changes have generally not occurred for al fe sc co y zr ree hf ta and th the relatively mobile elements have been redistributed over distances from 2 5 cm to more than 10 100 m and are associated mainly with zeolites and clays in thoroughly altered samples average whole rock changes in ti normalized mass range from about 0 5 17 g kg 9 49 for major elements and 0 1 280 mg kg 19 4260 for minor and trace elements compositional changes correlate with hydrothermal mineralogy the relatively immobile elements have been redistributed over a distance of at least 10 100 m but less than 2 5 cm and are associated mainly with clays in thoroughly altered samples addition of sio2 ranges from 110 890 g kg in samples where porosity has been thoroughly sealed by silica deposition thermal water is not in oxygen isotopic equilibrium with any primary or secondary phases analyzed except calcite modest depletions of 18o 1 2 due to exchange with thermal water apparently have occurred in y 8 plagioclase and obsidian oxygen isotope ratios in obsidian replacing smectite and in veinlet celadonite and cristobalite suggest that these phases precipitated from water locally enriched in 18o up to 8 heavier than present thermal water the minimum integrated water rock mass ratio in y 7 and y 8 is 103 104 assuming advective transport

differences in radiocarbon age between shell and charcoal from a holocene shellmound in northern california abstract the west berkeley shellmound the oldest well dated archaeological site in the san francisco bay region contains shell and charcoal ranging in age from ca 1200 to 5700 cal yr b p radiocarbon ages of marine shell and charcoal collected from fifteen stratigraphic levels in the west berkeley shellmound suggest changes in the 14 c content of san francisco bay surface waters relative to the atmosphere the oceanic reservoir age over the past 5000 yr the reservoir age of san francisco bay waters fluctuated between 870 and 170 14 c yr over the past 5000 yr with the lowest values occurring 2900 to 3800 cal yr b p and the highest values between 1200 and 2000 cal yr b p changes in the radiocarbon reservoir age may be due to changes in the strength of seasonal wind driven upwelling off coastal california where upwelling brings 14 c depleted waters to the surface the period of lowest r values at 3500 to 3900 cal yr b p is coincident with relatively low salinity in san francisco bay indicating high freshwater inflow and wet climate in california based on lake level records the period of high r values 1200 2000 cal yr b p is coincident with one of the driest periods in california during the late holocene these data suggest a link between coastal upwelling and precipitation over central california the age of the top of west berkeley mound and several other mounds in the san francisco bay region 1100 to 1300 cal yr b p coincides with a prolonged dry period in california and low river inflow to san francisco bay perhaps the sites were abandoned because of the drought

tectonic and magmatic responses to the subduction of high bathymetric relief subduction of high bathymetric relief such as aseismic ridges and magmatic plateaus is considered to be responsible for dramatic changes in the dynamics and kinematics of the subduction zone for example the buoyancy of high bathymetric relief is thought to flatten the dip of the subducting slab modifying the structural and magmatic evolution of the overriding plate and terminating arc volcanism in addition the effect of ridge subduction in retreating plate boundaries can inhibit subduction rollback a process that could locally pin the subduction hinge and lead to the development of cusps and slab tearing here we discuss the tectonic response to subduction of high bathymetric relief using examples from the circum pacific subduction systems we demonstrate that flattening of the subduction dip angle is only significant in the eastern pacific where the average slab dip angle is relatively shallow in the western pacific in contrast the average subduction dip angle is steeper and there is no significant flattening of the dip angle in areas of ridge subduction subduction of high bathymetric relief in the circum pacific is commonly associated with reduced arc volcanism and in many cases the area of ridge subduction coincides with a volcanic gap in the overriding plate ridge subduction is associated with pronounced changes in the style of deformation involving uplift reactivation of basement thrusts development of orogen perpendicular tear faults and block rotations leading to oroclinal bending the discussed characteristic patterns associated with ridge subduction provide important guidelines for reconstructing past plate tectonic processes and could help constraining the geodynamics of ancient subduction systems

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

the influence of wind forcing on the chesapeake bay buoyant coastal current observations of the buoyant coastal current that flows southward from chesapeake bay are used to describe how the thickness width and propagation speed vary in response to changes in the along shelf wind stress three basic regimes were observed depending on the strength of the wind for weak wind stresses from 0 02 to 0 02 pa the buoyant coastal current was relatively thin the front slope was not steep and the width was variable 1 20 km for moderate downwelling southward wind stresses 0 02 0 07 pa wind driven cross shelf advection steepened the front causing the plume to narrow and thicken for stronger downwelling wind stresses greater than 0 07 pa vertical mixing dominated bulk richardson numbers were approximately 0 25 isopycnals were nearly vertical and the plume front widened but the plume width did not change plume thickness and width were normalized by the theoretical plume scales in the absence of wind forcing normalized plume thickness increased linearly from 1 to 2 as downwelling wind stresses increased from 0 to 0 2 pa normalized plume widths were approximately 1 for downwelling wind stresses from 0 02 to 0 2 pa the observed along shelf propagation speed of the plume was roughly equal to the sum of the theoretical propagation speed and the wind driven along shelf flow

origin of mesozoic adakitic intrusive rocks in the ningzhen area of east china partial melting of delaminated lower continental crust to the best of our knowledge modern adakites have not been documented in a nonarc environment we report geochemical and isotopic data for early cretaceous anjishan adakitic intrusive rocks that are in a continental setting unrelated to subduction the anjishan adakitic intrusive rocks which are exposed in the ningzhen area of east china have high sr y and la yb ratios coupled with low yb and y as well as relatively high mgo contents and mg numbers mg 0 4 0 6 similar to products from slab melting however low n d t values 6 8 to 9 7 and high 8 7 sr 8 6 sr i 0 7053 0 7066 are inconsistent with an origin by slab melting the tectonics and geochemistry lead us to conclude that adakitic magmas were most likely derived from partial melting of mafic material at the base of the continental crust high sr y and la yb ratios of the adakitic intrusive rocks suggest that garnet was stable as a residual phase during partial melting implying that the crustal thickness exceeded 40 km in the early cretaceous the present thickness of the crust in the ningzhen area is only 30 km and therefore the crust appears to have been thinned by at least 10 km since the early cretaceous the relatively high mgo contents and mg of the anjishan intrusive rocks suggest that adakitic magmas interacted with mantle rocks possibly coinciding with lower crustal delamination which would also account for the observed thinning

postsubduction porphyry cu au and epithermal au deposits products of remelting of subduction modified lithosphere porphyry cu mo au and some epithermal au deposits are formed from hydrothermal fluids exsolved from cooling water rich calc alkaline magmas emplaced in volcanoplutonic arcs above subduction zones these magmas originate by partial melting of the metasomatized asthenospheric mantle wedge however there is increasing evidence for the existence of a suite of porphyry cu au and epithermal au deposits related to magmas generated after subduction beneath the arc has ceased associated magmas tend to be mildly alkaline relatively sulfur poor and emplaced as isolated complexes rather than in voluminous volcanoplutonic arcs they are likely formed by remelting of previously subduction modified arc lithosphere triggered by postsubduction lithospheric thickening lithospheric extension or mantle lithosphere delamination metasomatized mantle lithosphere or hydrous lower crustal cumulates residual from first stage arc magmatism contain small amounts of chalcophile and siderophile element rich sulfides and constitute a fertile source for hydrous au rich but relatively sulfur poor magmas during later remelting the recognition that porphyry cu au and related epithermal au systems can also form in postsubduction and collisional tectonic settings expands the range of geological environments and geographical terranes that are prospective for such deposits

giant versus small porphyry copper deposits of cenozoic age in northern chile adakitic versus normal calc alkaline magmatism cenozoic magmatic activity in northern chile led to the formation of two contrasting porphyry copper belts 1 a paleocene early eocene belt comprising small porphyry copper deposits e g lomas bayas of normal calc alkaline affinity and 2 a late eocene early oligocene belt hosting huge porphyry copper deposits e g chuquicamata of adakitic affinity although the first belt comprises both volcanic and plutonic rocks andesitic basaltic and rhyolitic lavas and tuffs and associated sub volcanic porphyries and felsic stocks the latter only includes intrusions mostly granodioritic types including porphyry copper deposits we suggest that the late eocene early oligocene belt formed when fast and oblique convergence between the south america and farallon plates led to flat subduction and direct melting of the subducting plate hence giving rise to plutonic rocks of adakitic affinity the absence of volcanism under prevailing compressional conditions prevented the escape of so2 from the adakitic sulfur rich highly oxidized magmas closed porphyry system which allowed formation of huge mineral deposits on the contrary coeval volcanic activity during formation of the paleocene early eocene calc alkaline porphyries allowed development of open systems hence to outgassing and therefore to small mineral deposits

geochronology and geochemistry of granitoids related to the giant dahutang tungsten deposit middle yangtze river region china implications for petrogenesis geodynamic setting and mineralization abstract porphyry and skarn deposits in the middle yangtze valley within the northern yangtze craton have a combined tungsten resource of 3 million tonnes mt and represent one of the most important tungsten regions in the world the dahutang porphyry tungsten deposit with reserves of 1 mt is one of the largest deposits uranium pb analyses for the ore related granitoids yield ages of 147 4 0 58 ma 148 3 1 9 ma for porphyritic biotite granite 144 7 0 47 ma 146 1 0 64 ma for fine grained granite and 143 0 0 76 ma 143 1 1 2 ma for granite porphyry a progressive youngling of ages that is consistent with field observations geochemical data show that the three types of granite are characterized by enrichments in rb pb and u and depletion in ba nb p and ti with asi molar al 2 o 3 cao na 2 o k 2 o 1 1 that is characteristic of a peraluminous melt the p 2 o 5 contents of the granites are 0 13 0 37 and have a positive correlation with sio 2 and they are thus s type intrusions they exhibit initial 87 sr 86 sr of 0 721 to 0 731 and e nd t of 5 06 to 7 99 for porphyritic biotite granite 0 7196 to 0 7289 and 6 29 to 6 74 for fine grained granite and 0 7153 to 0 7365 and 5 09 to 7 64 for granite porphyry chondrite normalized rare earth element ree patterns for the granites are characterized by enrichment in the light ree and a strong negative eu anomaly indicating that they were derived from the proterozoic pelitic and psammitic basement strata and experienced strong fractional crystallization of plagioclase our ca 150 140 ma age for the dahutang s type magmatism and w mineralization is identical to that of the i type magmatism related to cu au mo fe bearing porphyry and skarn deposits along the middle to lower yangtze river valley we propose that the latest jurassic to earliest cretaceous granitoids and ores formed during a tearing of the subducting izanagi slab which caused the upwelling of asthenosphere and resulting mantle crust interaction the s type granitoids and related w ore systems resulted from the re melting of the proterozoic crust whereas the i type granitic rocks and related ores are attributed to the partial melting of the subducted slab

2d electrical resistivity imaging of some complex landslides in lucanian apennine chain southern italy we use high resolution electrical resistivity imaging to delineate the geometry of complex landslides in the lucanian apennine chain of southern italy to identify the discontinuity between the landslide material and bedrock and to locate possible surfaces of reactivation the lucanian apennine chain is characterized by high hydrogeological hazard and shows a complete panorama of mass movements in this area all typologies of landslides markedly predisposed and tightly controlled by the geostructural characteristics are found rotational and translational slides rototranslational slides earth and mudflows as well as deep seated gravitational slope phenomena with a predominance of rototranslational slides evolving as earthflow slides three test sites characterized by complex geology and a high hydrogeologic hazard are studied the giarrossa and varco izzo earthflow slides are located to the west and east of the town of potenza whereas the latronico slide is located close to the town of latronico

petrogenesis and oxidation state of granodiorite porphyry in the jurassic chuankeng skarn cu deposit south china implications for the cu fertility and mineralization potential abstract large scale jurassic porphyry skarn cu mineralization in the qin hang metallogenic belt of south china has attracted much attention but comparative studies of porphyries in large and small scale deposits are lacking in this paper we present new zircon u pb ages trace element composition and hf isotopic composition as well as whole rock geochemical and sr nd isotopic compositions for the porphyries associated with mineralization in the small scale chuankeng cu deposit drawing on our data for the chuankeng deposit and existing data for the nearby giant dexing cu deposit we aim to identify factors controlling the mineralization potential of both deposits granodiorite porphyries of chuankeng deposit were emplaced at ca 161 158 ma they have moderate sio2 contents of 61 9 66 1 wt and high sr y 59 135 and la yb n 4 14 ratios their high mgo contents 0 2 2 9 wt lack of negative eu anomaly depletion in y and yb relatively high initial 86sr 87sr ratios 0 7076 0 7078 and low end t values 4 5 to 4 9 indicating that the chuankeng porphyries were derived from partial melting of delaminated lower crust the middle late jurassic chuankeng porphyries are considered to have been formed in a localized intra continental extension environment along the jiangshao fault in response to far field stress from paleo pacific plate subduction although no middle late jurassic magmatic arc rocks have been found in the study area the chuankeng porphyries display similar characteristics to arc rocks on the basis of their zircon ehf t values 2 6 to 0 9 two stage hf model ages 1 4 1 1 ga and regional geological history we infer that magma source of chuankeng porphyries were mainly neoproterozoic juvenile crust with the involvement of paleoproterozoic ancient crust thus their arc like features were inherited from the neoproterozoic juvenile crust that formed by subduction of oceanic crust during the jiangnan orogeny chuankeng porphyries have lower zircon ce4 ce3 and higher ti in zircon temperatures and lower whole rock end and zircon ehf values than the dexing porphyries indicating they are less oxidized and less hydrous and with more involvement of the ancient crustal material in the magma source which could explain the relatively small scale cu mineralization in chuankeng this study highlights the values of integrated studies of whole rock nd and zircon trace element and hf isotopic compositions in assessing the potential for cu mineralization

remelting of neoproterozoic relict volcanic arcs in the middle jurassic implication for the formation of the dexing porphyry copper deposit southeastern china article i nfo the dexing copper deposit in southeastern china is a typical non arc porphyry deposit the origin of which has been a topic of debate for several decades here we present new results from u pb geochronology whole rock chemistry and sr nd hf o isotopic investigations on the ore forming granodioritic porphyry la icpms zircon u pb data suggest that the granodioritic porphyry was formed in the middle jurassic ca 172 5 ma probably associated with lithospheric thinning driven by either sub continental lithospheric mantle delami nation or asthenospheric upwelling the porphyry displays both arc like and adakitic trace element signa tures the adakitic features suggest that hree heavy rare earth elements rich minerals such as garnet and hornblende in the absence of plagioclase resided in the source region the arc like signatures are broadly comparable with those of the proximal neoproterozoic island arc rocks including the keratophyre from shuangxiwu group and associated granitoids indicating a potential genetic relationship the porphyry has chondritic end t of 0 28 to 0 25 and radiogenic ehf t of 2 to 7 and correspondingly uniform two stage depleted mantle nd model ages of 940 980 ma and hf model ages of 800 1100 ma mean 920 ma on nd and hf isotopic evolution diagrams these values are markedly similar to those of the adjacent neoproterozoic arc rocks when calculated forward to the mid jurassic zircons of the porphyry show mantle like oxygen isotope characters with 18 o values clustering in the range of 4 7 5 9 similar to the values for the neoproterozoic arc rocks mentioned above the geochemical and isotopic features recorded in our study suggest mantle derived magmas with no significant supracrustal input for the source of the por phyry with regard to the source of the cu ore we consider a model involving the remelting of sulfide bearing arc related lower crustal source furthermore the occurrence of a neoproterozoic vms volcanic massive sulfide type copper deposit the pingshui cu deposit in the shuangxiwu group might suggest that the lower crustal rocks related to a neoproterozoic relict island arc provided the source for copper during a second stage melting event we propose a new geodynamic model for the dexing porphyry cu deposit which envis ages that the sulfide bearing arc lower crustal rocks were generated during oceanic slab subduction in the early neoproterozoic the remnants of which were preserved at the crust mantle boundary subsequently in the middle jurassic these rocks were heated by asthenospheric upwelling and remelted to produce fertile magmas the magmas ascended along the northeast jiangxi fault and intruded into the jiuling terrane where cu precipitation occurred upon subsequent magma cooling and fluid exsolution

multiproxy evidence of holocene climate variability from estuarine sediments eastern north america water temperature estimated from ostracode mg ca ratios the results indicate a much drier early holocene in which mean paleosalinity was 28 ppt in the northern bay falling 25 to 20 ppt during the late holocene early holocene mg ca derived temperatures varied in a relatively narrow range of 13 to 16 c with a mean temperature of 14 2 c and excursions above 16 c the late holocene was on average cooler mean temperature of 12 8 c in addition to the large contrast between early and late holocene regional climate conditions multidecadal 20 40 years salinity and temperature variability is an inherent part of the region s climate during both the early and late holocene including the medieval warm period and little ice age these patterns are similar to those observed during the twentieth century caused by nao related processes comparison of the midlatitude chesapeake bay salinity record with tropical climate records of intertropical convergence zone fluctuations inferred from the cariaco basin titanium record suggests an anticorrelation between precipitation in the two regions at both millennial and centennial timescales

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

cretaceous granitic intrusions in fujian province cathaysia block implications for slab rollback and break off of the paleo pacific plate abstract the geodynamic transformation of the cathaysia block and its relationship with the cretaceous granitic intrusions have been controversial in recent decades in this study petrology zircon u pb ages lu hf isotopic composition whole rock geochemistry and sr nd isotopes were carried on cretaceous granites that were collected from the fujian province se china combining previously published ages with the new ages obtained in this study indicates that the magmatism in the study area occurred in three distinct stages at 145 137 ma 136 118 ma and 107 86 ma the first stage i type granites were intruded at 137 1 ma and 145 1 ma which are characterized by low end t values of 7 3 to 6 8 and ehf t values of 12 5 to 2 5 it was formed by partial melting of mesoproterozoic medium to high k basaltic rocks in the thickened crust of 40 km without significant hybridization of mantle derived magmas and fractional crystallization the second stage highly differentiated i type granites yield zircon u pb ages of 125 1 ma and 128 1 ma which contain slightly negative end t values of 5 4 to 5 3 and ehf t values of 8 4 to 3 2 it was generated by partial melting of the mesoproterozoic basement at the depth of 30 40 km triggered by underplating of a small amount of mantle derived magma with primary crustal melts undergoing plagioclase dominated fractionation crystallization the third stage i type granites yield zircon u pb ages of 104 1 ma and 105 1 ma which contain end t values of 1 7 to 7 3 and ehf t values of 6 0 to 0 5 it was derived from partial melting of mesoproterozoic basaltic source at a depth of 30 km besides a mass of mantle derived magma was mixed into the crustal melts accompanied with plagioclase dominated fractionation crystallization combining previously published data and those obtained in this study provides significant information for the tectonic evolution of paleo pacific in stage 1 145 137 ma the existence of i type granites and adakitic rocks suggests that the dip angle subduction of the paleo pacific plate led to the partial melting of the thickened lower crust under the compressional environment in stage 2 136 118 ma the generation of i type and a type granitic magmas imply the thinning of the lithospheric crust under the extensional environment and the upwelling of the asthenospheric mantle which are caused by slab rollback of paleo pacific in stage 3 107 86 ma the appearance of much more i type and a type granites indicates that the break off of the paleo pacific plate led to much stronger crust mantle interactions under the extensional environment

the palaeogeography of mesolithic settlement subsistence and shell midden formation in the muge valley lower tagus basin portugal this paper reports the first detailed palaeogeographical analysis of the environmental context of late mesolithic shell midden sites in the lower tagus area and focuses on the lower muge valley which contains an internationally significant mesolithic record the lower muge valley fill comprises buried estuarine and fluvial environments contemporary with mesolithic settlement holocene environmental and palaeogeographic changes influenced mesolithic settlement subsistence and midden accumulation the sudden appearance of large late mesolithic shell middens throughout portugal represents a process of increased visibility and preferential preservation of the archaeological record prior to 6100 cal bc aggrading valley floor environments did not occupy the entire width of the present lower tagus floodplain and any sites located in the early holocene valley are currently deeply buried shell midden occupation on terrace levels followed the establishment of aggrading estuarine environments containing produ

the medieval climate anomaly and little ice age in chesapeake bay and the north atlantic ocean abstract a new 2400 year paleoclimate reconstruction from chesapeake bay cb eastern us was compared to other paleoclimate records in the north atlantic region to evaluate climate variability during the medieval climate anomaly mca and little ice age lia using mg ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation driven estuarine hydrography results show that warmest temperatures in cb reached 16 17 c between 600 and 950 ce common era centuries before the classic european medieval warm period 950 1100 ce and peak warming in the nordic seas 1000 1400 ce a series of centennial warm cool cycles began about 1000 ce with temperature minima of 8 to 9 c about 1150 1350 and 1650 1800 ce and intervening warm periods 14 15 c centered at 1200 1400 1500 and 1600 ce precipitation variability in the eastern us included multiple dry intervals from 600 to 1200 ce which contrasts with wet medieval conditions in the caribbean the eastern us experienced a wet lia between 1650 and 1800 ce when the caribbean was relatively dry comparison of the cb record with other records shows that the mca and lia were characterized by regionally asynchronous warming and complex spatial patterns of precipitation possibly related to ocean atmosphere processes

monitoring landslides with geophysical and geodetic observations the objective of this study was to evaluate and predict land movement by integrating geodetic geophysical and meteorological data in a landslide area specifically electrical resistivity tomography surveying global navigation satellite system and terrestrial laser scanning techniques were integrated to monitor a landslide the study area lies to the southeast of the town of taskent in southern turkey close to balcilar in the central taurus mountain chain landslides result in considerable damage to structures farmland and the environment in this area therefore it is important to characterise the size extent and timing of past land movements in order to mitigate damage from future landslides analysis presented in this paper shows that the greatest land movements in the region occur in spring when average motions can be up to 1 5 m per month it is demonstrated that integrated techniques provide a better means for monitoring landslide processes and gathering data for predictions of future movements mapping landslide movements by integrating geophysical and geodetic observations can provide a meaningful evaluation of a landslide and its dynamics

molybdenite re os dating zircon u pb age and geochemistry of granitoids in the yangchuling porphyry w mo deposit jiangnan tungsten ore belt china implications for petrogenesis mineralization and geodynamic setting abstract the yangchuling w mo deposit located in the jiangnan porphyry skarn jnb tungsten ore belt is the first recognized typical porphyry w mo deposit in china in the 1980 s stockworks and disseminated w mo mineralization occur in the roof pendant of a 0 3 km 2 monzogranitic porphyry stock that intruded into a granodiorite stock hosted by neoproterozoic phyllite and slate la icpms zircon u pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143 8 0 5 ma and 149 8 0 6 ma respectively six molybdenite samples yielded a re os weighted mean age of 146 4 1 0 ma geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements lile relative to high field strength elements hfse indicating a peraluminous nature a cnk 1 01 1 08 two granitoids are characterized by a negative slope with significant light ree heavy ree fractionation la yb n 8 38 23 20 and negative eu anomalies eu eu 0 69 0 76 the p 2 o 5 contents of the yangchuling granitoids range from 0 12 to 0 17 and exhibit a negative correlation with sio 2 reflecting that they are highly fractionated i type they have high initial 87 sr 86 sr ratios 0 7104 0 7116 low negative e nd t 5 05 to 5 67 and homogeneous e hf t between 1 39 and 2 17 indicating similar sources additionally two stage nd model ages t dm2 of 1 3 1 4 ga and two stage hf model ages t dm2 of 1 2 1 3 ga are consistent indicating that neoproterozoic crustal rocks of the shuangqiaoshan group could have contributed to form the yangchuling magmas considering the two groups of parallel late mesozoic ore belts namely the jiangnan porphyry skarn tungsten belt jnb in the south and the middle lower yangtze river porphyry skarn cu au mo fe ore belt yrb in the north the nanling granite related w sn ore belt nlb in the south the neighboring qin hang porphyry skarn cu mo hydrothermal pb zn ag ore belt qhb in the north as well as the southeastern coast porphyry skarn cu mo au ore belt scb recognized in south china in this paper we propose that the latest jurassic to earliest cretaceous granitoids and associated ores were formed during a tearing of the subducting izanagi slab this tearing of the subduction slab caused the upwelling of asthenosphere and the resulting mantle crust interaction the granitoid related w ore systems in jnb resulted from the remelting of the proterozoic crust the mafic ultramafic volcanic rocks of the shuangqiaoshan group intercalated with phyllite and slate ophiolitic melange and magmatic arc rocks mainly comprising i type granite basalt andesite rhyolite pyroclastics together with subduction related metasomatized lithospheric mantle would have provided additional mantle material in this case the partial melting of rocks of the shuangqiaoshan group can produce s i and transitional type granitoids after strong differentiation it formed tungsten bearing granitoids characterized by enrichment of high alkali silicon and volatile components in the yangchuling mine area the small monzogranitic porphyry stock has stronger fractionation volatile content and ore forming components than the older granodiorite resulting in the development of the porphyry w mo ore system

trends in chesapeake bay sedimentation rates during the late holocene abstract trends are discernible in the estimates of late holocene rates of sedimentation and sea level rise for the chesapeake bay during most of the holocene epoch sedimentation rates and relative sea level rise were equal within the limits of measurement at approximately 1 mm yr 1 sedimentation rates measured over the past century however are nearly an order of magnitude higher while the rate of relative sea level rise for the chesapeake bay now averages 3 3 mm yr 1 as measured on long term tide gauge records when the acceleration in these rates occurred is uncertain but it appears to have been confined to the past millennium and probably to the past few centuries the rapid sedimentation rates recorded during historic time may be a temporary disequilibrium that has resulted from a recent acceleration in the rate of relative sea level rise

copperore potential of adakitic intrusives in gangdese porphyry copper belt constrains from rock phase and deep melting process the gangdese porphyry cu mo system in southern tibet 13 6 16 9 ma was generated during the post collision crustal extension the pre ore porphyries mainly consist of granodiorite porphyries with ages older than 17 ma whereas the porphyries of the ore forming stage are mostly composed of monzonitic granite and adamellite porphyries with zircon shrimp ages ranging between 14 5 and 17 6 ma the post ore porphyries are comprised of granite porphyries with a young ar ar age of 11 2 ma geochemical studies indicate that these porphyries are of shoshonitic and high k calc alkaline series and show geochemical affinity with adakites derived from partial melting of a thickened basaltic lower crust the pre ore porphyries have the lowest contents of ree 27 10 6 45 10 6 y 2 9 10 6 3 4 10 6 and the lowest sm yb ratio 3 0 4 9 coupled with the highest zr sm ratio 50 118 the post ore porphyries have the highest contents of ree 122 10 6 197 10 6 and y 8 2 10 6 and intermediate ratios of sm yb 5 9 6 2 and zr sm 34 44 the porphyries of the ore forming stage are transitional between the pre and post ore porphyries in terms of y content and sm yb and zr sm ratios but their sr nd isotopic signature is similar to that of the adakitic rocks from cordillera blanca major trace elements and sr nd geochemistry of these adakitic porphyries indicates that partial melting of a thickened lower crust beneath southern tibet involves input of materials derived from the depleted mantle which provides necessary heat and metals cu au for the generation of cu bearing adakitic melts upward migration of the melt zone from basal amphibole eclogite to upper garnet amphibolite proceeds gradually with time but the transition of residual phase from amphibole bearing to garnet bearing assemblages in the garnet amphibolite source during melting is the fundamental and important process for the formation of the fertile adakite and porphyry cu systems in southern tibet

multi stage fluid boiling and formation of the giant fujiawu porphyry cu mo deposit in south china abstract the fujiawu cu mo deposit is located in the southeastern part of south china mineralization and alteration at fujiawu include stage 1 barren quartz k feldspar biotite veins and stage 2 quartz molybdenite veins with potassic alteration stage 3 quartz pyrite chalcopyrite veins with phyllic alteration and stage 4 barren quartz pyrite calcite chlorite epidote veins with propylitization two phase liquid rich type i two phase gas rich type ii and halite bearing type iii aqueous inclusions were identified at fujiawu the last two types of fluid inclusions are absent in stages 1 and 4 type i inclusions in stage 1 veins demonstrate homogenization temperatures th of 409 to 556 c with salinities of 7 8 14 4 wt nacl equivalent type iii inclusions that homogenize by vapor bubble disappearance type iii a and coexisting type ii inclusions in stage 2 veins have th of 370 460 c and 374 505 c with salinities of 37 9 52 7 and 3 1 8 2 wt nacl equivalent respectively type iiia inclusions that homogenize by vapor bubble disappearance and coexisting type ii inclusions in stage 3 veins yield th 277 454 c and 323 450 c with salinities of 33 5 49 8 and 1 5 7 9 wt nacl equivalent respectively type i inclusions in stage 4 have th of 146 to 279 c with salinities lower than 4 9 wt nacl equivalent type iii inclusions that homogenize by halite disappearance type iii b in stages 2 and 3 of veins were not formed during fluid boiling processes and could yield extremely high trapping pressures the abundant presence of boiling fluid inclusion assemblages at fujiawu suggests that extensive multi stage boiling events promoted the large scale cu mo mineralization type iiib inclusions cannot be regard as the end member of boiling inclusion assemblages and cannot be used to calculate trapping conditions the estimated trapping pressures estimated by type iiia inclusions are 132 to 284 bars and 44 to 264 bars in stages 2 and 3 respectively re os dating of molybdenite gives a weighted average 187 re 187 os model age of 172 1 ma in response to a localized extensional environment due to a far field stress at the south china plate margin resulting from the initial paleo pacific plate northwestward subduction the high re contents in molybdenite in combination of previously reported high mgo contents of ore related porphyries and regional history indicate that ancient subduction modified lithospheric mantle was crucial for the fujiawu cu mo deposit