complete dynamic modeling calibration for the thurwieser rock avalanche italian central alps abstract few rock avalanches have been witnessed and no exact real time description is available the 2 5 m m 3 punta thurwieser rock avalanche september 2004 italian central alps is a unique event for which many quantitative observations have been gathered this is the first case ever of a natural rock avalanche being recorded on video and for which an almost exact value of the total time duration from initial detachment to final deposition is available the landslide travelled over 2 9 km from its source partially in a glacial environment the initial failure and the time for the complete evacuation of the source area were studied and assessed by a series of photos the mean front velocities along the path have been estimated from the video the final geometry and the characteristics of the deposit have been obtained by gps measurements aerial photos field surveys and laboratory tests a quasi 3d continuum dynamic analysis of the landslide motion has been performed assuming both a voellmy and a frictional rheology in the model dan 3d for the first time the landslide front velocities have been used for back analyses and calibration of the rheological parameters together with the final shape and thickness of the deposit and its developing extension the dynamic flow resistance parameters initially calibrated with dan were adopted and validated in dan 3d showing good consistency they are consistent with the existing database for calibrated landslides of similar type and scale flow velocities on the path segment underlain by glacial deposits up to 55 65 m s 1 are more accurately predicted by adopting a frictional rheology up to 50 55 m s 1 with zero pore pressure and a 26 friction angle than by a voellmy rheology up to 40 45 m s 1 both observations and modelling show that glacial ice plays a substantial role in increasing the rock avalanche mobility

modeling the role of sodic alteration in the genesis of iron oxide copper gold deposits eastern mount isa block australia liberation of iron and potassium by widespread postmetamorphic albitization of country rocks was one of the likely contributing processes in the formation of both barren and mineralized magnetite chalcopyrite biotite gold hematite clinopyroxene actinolite apatite ironstones in the cloncurry district of the proterozoic mount isa block whole rock geochemical data indicate nearly immobile al ga ti zr during transformation of a variety of least altered rocks toward albitite the data indicate that the addition of na from a brine to the rock accompanied the loss of fe k ba rb ca sr co v mn pb and zn from those altered rocks and enrichment in the brine but that cu was not systematically stripped from a variety of wall rocks during albitization conversely the formation of metasomatic ironstones the immediate hosts to some cu au ores involves addition of most of the same elements that were lost during albitization the correlation between intensity of alteration its distribution and timing e g in breccias cored by ca 1530 1500 ma granitoids and convergence of all rock types toward magmatic stable isotope values provides strong evidence for a substantial component of igneous derived fluid simulations of the albitization process were carried out isothermally at 550 c and 350 mpa and polythermally from these conditions down to 400 c and 200 mpa using the gibbs minimization method with hch software and the unitherm database both simple fluid rock mixing models and more complicated reactor style algorithms used a range of input fluids from fluids equilibrated fluid with two feldspar granite through to na k ratios consistent with fluid inclusion results and geochemical data for initially unaltered wall rocks the apparent paradox of widespread albitization resulting from fluid released by two feldspar granites can be explained by relatively small shifts away from the k feldspar albite equilibrium curve and even isothermal model fluids derived from two feldspar granites produce albitites in calc silicate rocks outboard of granite proximal k feldspar clinopyroxene skarns matching field patterns those models with fluid na k ratios similar to those of fluid inclusions produced the most realistic alteration assemblages dominated by albite for both isothermal conditions and decreasing temperature which approximate those observed in the field pixe and microthermometric data on fluid inclusions from quartz in two feldspar quartz monzonite and pegmatite at the top of the mount angelay pluton indicate bulk na k molar ratios in the fluid of between 10 and 20 considerably higher than our thermodynamically calculated values for fluid in equilibrium with two feldspar granite of around 3 at 550 c 350 mpa such shifts may have been attained by admixture of magmatic hydrothermal fluid with small amounts of nacl brines trapped along grain boundaries in scapolite bearing calc silicate wall rocks by fluid immiscibility due to high initial co2 contents in the felsic intrusions by contributions from mafic magmas or from dissolution of salt rich layers into the intrusions prior to crystallization and fluid release with increasing amounts of fluid rock interaction in the models the fluids were enriched in k fe and ca approaching compositions observed in fluid inclusions in the ore deposits these fluids reacted with pelitic rocks which are common ore hosts would produce magnetite clinopyroxene biotite actinolite alteration at high temperature similar to the proximal alteration around ore deposits we infer that precipitation of sulfides in the cu au deposits was the result of mixing of cu bearing brine of ultimately magmatic origin but modified extensively via albitization with sulfur bearing fluids or reaction of the brine with sulfur bearing rocks when cu was absent from the initial magmatic fluid barren ironstones may have been the result

the stable isotope signature of kilometre scale fracturedominated metamorphic fluid pathways mary kathleen australia abstract large calcite veins and pods in the proterozoic corella formation of the mount isa inlier provide evidence for kilometre scale fluid transport during amphibolite facies metamorphism these 10 to 100 m scale podiform veins and their surrounding alteration zones have similar oxygen and carbon isotopic ratios throughout the 200 10 km mary kathleen fold belt despite the isotopic heterogeneity of the surrounding wallrocks the fluids that formed the pods and veins were not in isotopic equilibrium with the immediately adjacent rocks the pods have 13ccalcite values of 2 to 7 and 18ocalcite values of 10 5 to 12 5 away from the pods metadolerite wallrocks have 18owhole rock values of 3 5 to 7 and unaltered banded calc silicate and marble wallrocks have 13ccalcite of 1 6 to 0 6 and 18ocalcite of 18 to 21 in the alteration zones adjacent to the pods the 18o values of both metadolerite and calc silicate rocks approach those of the pods large calcite pods hosted entirely in calc silicates show little difference in isotopic composition from pods hosted entirely in metadolerite thus 100 to 500 m scale isotopic exchange with the surrounding metadolerites and calc silicates does not explain the observation that the 18o values of the pods are intermediate between these two rock types pods hosted in felsic metavolcanics and metasiltstones are also isotopically indistinguishable from those hosted in the dominant metadolerites and calc silicates these data suggest the veins are the product of infiltration of isotopically homogeneous fluids that were not derived from within the corella formation at the presently exposed crustal level although some of the spread in the data may be due to a relatively small contribution from devolatilization reactions in the calc silicates or thermal fluctuations attending deformation and metamorphism the overall l shaped trend of the data on plots of 13c vs 18o is most consistent with mixing of large volumes of externally derived fluids with small volumes of locally derived fluid produced by devolatilization of calc silicate rocks localization of the vein systems in dilatant sites around metadolerite calc silicate boundaries indicates a strong structural control on fluid flow and the stable isotope data suggest fluid migration must have occurred at scales greater than at least 1 km the ultimate source for the external fluid is uncertain but is probably fluid released from crystallizing melts derived from the lower crust or upper mantle intrusion of magmas below the exposed crustal level would also explain the high geothermal gradient calculated for the regional metamorphism

the lightning creek sill complex cloncurry district northwest queensland a source of fluids for fe oxide cu au mineralization and sodic calcic alteration the lightning creek cu au prospect is hosted by a cogenetic suite of plutonic i type granitoids the dominant rock type is a porphyritic quartz monzodiorite that is intruded by more fractionated rocks including monzogranite and alkali feldspar granite a series of flat lying sills are interpreted to be late stage differentiates based on their timing mineralogy and chemistry in parts of the prospect there is pervasive sodic calcic alteration pyroxene after amphibole albite after k feldspar and oligoclase of the plutonic rocks this alteration predates sill emplacement and is unrelated to veining or fracturing of any kind the presence of small amounts of carbonate in the altered rocks suggests that the fluids were co2 bearing quartz and feldspar separates from these altered rocks have oxygen isotope compositions similar to those from fresh quartz monzodiorite suggesting that the fluids were hot and of magmatic composition sodium and ca were added and k fe cl and cu were stripped during what is interpreted as an autometasomatic event the sills display considerable textural and mineralogical complexity and evolved from equigranular quartzofeldspathic rocks aplites with magmatic chemistry to unusual fe rich rocks albite magnetite quartz that exhibit a range of bizarre spherulitic textures some of the albite and magnetite in the sills is secondary albite forms pseudomorphs after k feldspar na fe ca alteration along sill margins and within sills at the contacts between different textural zones halos of disseminated magnetite clinopyroxene fe ca na alteration are developed adjacent to early magnetite veins fluid inclusion studies indicate that these rocks crystallized at temperatures in excess of 500 c and at pressures in excess of 1 5 kbar the range of spherulitic textures is taken to indicate crystallization under hydrous conditions with the episodic release of a fluid phase this magmatic fluid phase was dominated by h2o co2 and chlorine and underwent phase separation into a co2 rich vapor and a hypersaline brine 33 55 wt nacl equiv the hypersaline fluid was enriched in fe 10 wt and cu 1 wt pixe analysis in addition to na k and ca where this fluid was retained within fe rich portions of the sills it caused ca fe na alteration pyroxene albite magnetite growth at the expense of quartz where the fluid was expelled from the sills it produced quartz magnetite clinopyroxene albite veins broadly coeval with the early magnetite veins although rich in cu these granitoid derived magmatic fluids did not generate significant cu au mineralization perhaps because of the high temperatures involved and or a lack of reduced sulfur in the fluids or host rock however the amount of iron present is estimated from the aeromagnetic anomaly to be in excess of 2 000 million tonnes mt a later generation of calcite chlorite pyrite chalcopyrite veins contain traces of cu au mineralization fluid inclusion and stable isotope work indicate that these veins probably crystallized from cooler 200 c more dilute 15 28 wt nacl equiv fluids perhaps generated by the admixture of a meteoric component the conclusions reached in this study have implications for understanding the genesis of fe oxide cu au deposits and related sodic calcic alteration the study indicates the potential for co2 rich granitoid magmas to evolve hypersaline fe and cu rich fluids capable of causing intense magnetite veining and cu au mineralization autometasomatic sodic calcic alteration of the granitoids may be an important precursor to mineralization contributing fe k cu and cl to the magmatic fluids

kiruna type deposits their origin and relationship to intermediate subvolcanic plutons in the great bear magmatic zone northwest canada magnetite apatite actinolite rocks similar to those at kiruna sweden and the st francois mountains missouri are associated with seven epizonal plutons that intrude andesitic stratovolcanoes of a broadly folded early proterozoic continental magmatic arc located in the northwestern canadian shield the plutons mainly medium grained quartz monzonite monzodiorite diorite iugs sheets and laccoliths 5 to 25 km in diameter are spatially temporally and compositionally related to host andesitic stratovolcanoes they were emplaced at 2 to 3 km depth are compositionally heterogeneous metasomatically altered and had plagioclase as the liquidus phase in addition they have kilometer wide alteration halos comprising an inner zone of nearly complete wall rock albitization an intermediate zone of magnetite apatite actinolite veins pods breccias and wall rock replacement and an outer zone of disseminated sulfides one pluton balachey has a halo that is more or less completely outside the body but another rainy lake has a halo that is partly superimposed over it separation of iron phosphate and silicate melts by liquid immiscibility is not supported by 1 the gradual replacement of plagioclase by chessboard albite toward the roof of the rainy lake pluton 2 the chemical trends in the rainy lake intrusion 3 the mineralogical zoning low temperature mineralogy and replacement textures of the magnetite apatite actinolite and 4 the relationship of the magnetite apatite actinolite veins and bodies to the plutons however all available data are compatible with a deuteric origin it is concluded that high temperature low initial water content and shallow level emplacement by intermediate plutons are necessary for the development of kiruna type deposits

debris flow analyst da a debris flow model considering kinematic uncertainties and using a gis platform abstract although the main driving force of debris flows is simply gravity the dynamic processes are very complex kinematic uncertainties during motion make it difficult to exactly simulate debris flows in traditional numerical simulation models of debris flows the kinematic uncertainties are generally not considered in the lagrangian description in addition the challenge of obtaining accurate simulation parameters further suggests the necessity of probabilistic modeling of debris flows in this study a novel statistical debris flow simulation model debris flow analyst model is proposed in the lagrangian description in which the inherent stochasticity in the motion of a debris flow is described by stochastic differential equations sdes in this model the accelerations of moving debris are calculated by newton s second law and their locations are estimated based on monte carlo simulation according to case studies the proposed model provides results close to the analytical solution in a 1 d simulation of dam breaks in the eulerian description and reduces some numerical oscillations additionally the debris flow analyst model can produce reasonable results based on a single phase rheological model in 2 d simulations of a debris flow in tibet and a flow like landslide triggered by storms on 4 5 november 1993 in hong kong from the theoretical perspective our model is equivalent to the total variation diminishing tvd scheme in the eulerian description in addition the statistical model provides a new tool to estimate kinematic uncertainties in the hazard analysis of debris flows on gis platforms

palaeoenvironments palaeogeography and physiography of a large shallow muddy ramp late cenomanian turonian kaskapau formation western canada foreland basin the kaskapau formation spans late cenomanian to middle turonian time and was deposited on a low gradient shallow storm dominated muddy ramp dense well log control coupled with exposure on both proximal and distal margins of the basin allows mapping of sedimentary facies over about 35 000 km2 the studied portion of the kaskapau formation is a mudstone dominated wedge that thins from 700 m in the proximal foredeep to 50 m near the forebulge about 300 km distant regional flooding surfaces permit mapping of 28 allomembers each of which represent an average of ca 125 kyr more than 200 km from shore calcareous silty claystone predominates whereas 100 to 200 km offshore mudstone and siltstone predominate from about 30 to 100 km offshore centimetre bedded very fine sandstone and mudstone record along shelf sse directed storm generated geostrophic flows five to thirty kilometres from shore decimetre bedded hummocky cross stratified fine sandstone and mudstone record strongly oscillatory wave dominated flows whereas some gutter casts indicate shore oblique apparently mostly unidirectional geostrophic flows nearshore facies are dominated by swaley cross stratified or intensely bioturbated clean fine sandstone interpreted as recording respectively areas strongly and weakly affected by discharge from distributary mouths shoreface sandstones grade locally into river mouth conglomerates and sandstones including conglomerate channel fills up to 15 m thick locally brackish lagoonal shelly mudstones are present on the extreme western margin of the basin there is no evidence for clinoform stratification which indicates that the kaskapau sea floor had extremely low relief lacked a shelf slope break and was probably nowhere more than a few tens of metres deep the absence of clinoforms probably indicates a long term balance between rates of accommodation and sediment supply mud is interpreted to have been transported 250 km offshore in a sea bed nepheloid layer repeatedly re suspended by storms fine grained sediment accumulated up to a mud accommodation envelope perhaps only 20 to 40 m deep continuous re working of the sea floor by storms ensured that excess sediment was redistributed away from areas that had filled to the accommodation envelope being deposited in areas of higher accommodation further down the transport path the facies distributions and stratal geometry of the kaskapau shelf strongly suggest that sedimentary facies especially grain size were related to distance from shore not to water depth as a result the 100 to 300 m depth interpreted from calcareous claystone facies for the more central parts of the interior seaway might be a significant overestimate

maccormack tvd finite difference solution for dam break hydraulics over erodible sediment beds abstractcoupled shallow water equations integrated with sediment transport and morphological evolution are presented in this paper the momentum exchange terms that originated from the interaction between flow and sediment which were ignored by several researchers are taken into account the time and space second order maccormack total variation diminishing tvd finite difference method is used to solve these equations a series of numerical simulations compared with laboratory dam break experiments were carried out the simulated results are in good agreement with experimental measured results which demonstrates that the current computational framework is able to determine the dam break hydraulics over erodible sediment

landslide hazard spatial analysis and prediction using gis in the xiaojiang watershed yunnan china abstract the xiaojiang watershed in southwest china has high landslide hazard and has been given the title of the museum of geohazards in china however the available information on landslides in the xiaojiang watershed is still limited we constructed the essential spatial database of landslides using the gis techniques the quantitative relationships between landslides and factors affecting landslides are established by the certainty factor model cf the affecting factors such as lithology structure slope angle slope aspect elevation and off fault distance are recognized by applying cf value integration and landslide zonation the most significant affecting factors are selected the widespread landslide activities in the xiaojiang watershed are caused and triggered by heavy rain a promising approach to modeling the spatial distribution of rainfall triggered landslide is combining the mechanistic infinite slope stability model with a hydrological model a model modified from stability index mapping sinmap is used to prepare the landslide susceptibility maps for different rainfall conditions information on these maps could be useful for explaining the known existing landslide making emergency decisions and relieving the efforts on the avoidance and mitigation of future landslide hazards

ichthyornis aves from the early turonian late cretaceous of alberta an isolated left humerus from the cretaceous toothed bird ichthyornis is described the fossil comes from the vimy member of the kaskapau formation at watino alberta and is early turonian in age the watino specimen is the oldest well authenticated record of ichthyornis and the oldest cretaceous skeletal fossil of a bird from the western hemisphere the wide geographic distribution of ichthyornis within the western interior of north america is in keeping with nomadic habits as inferred from strongly flying modern marine birds

geology chronology fluid inclusions and h o s isotopic compositions of the hongyuntan magnetite deposit eastern tianshan nw china abstract the hongyuntan magnetite deposit which is located in the aqishan yamansu belt of eastern tianshan xinjiang is hosted within carboniferous submarine volcanic sedimentary sequences the deposit is characterized by five metallogenic stages stage i garnet diopside stage ii magnetite tremolite chlorite pyrite stage iii magnetite quartz albite actinolite stage iv pyrite quartz epidote and stage v hematite limonite pyrite associated with magnetite formed during the stage ii has a re os isochron age of 324 31 ma four types of fluid inclusions were observed in the mineral assemblages namely two phase liquid and vapor inclusions multi phase daughter mineral bearing inclusions multi phase co2 bearing inclusions and monophase vapor inclusions microthermometry data reveal that the ore forming fluids evolved from high temperature average 532 5 c and high salinity average 26 9 wt nacleqv fluids to moderate low temperature average 203 6 c and low salinity 5 07 wt nacleqv fluids magnetite precipitation may have been greatly assisted by mixing and boiling in stage ii and stage iii respectively the hydrogen and oxygen isotopic values of stage i garnet dv smow 107 9 to 76 7 18ofluid 6 4 10 7 and stage iii quartz dv smow 85 5 to 83 2 18ofluid 3 8 4 7 indicate that the ore forming fluids were dominated by magmatic water whereas fluid mixing occurred during stage ii dv smow 117 3 to 112 6 18ofluid 3 3 5 7 and stage iv dv smow 115 2 to 58 5 18ofluid 1 3 to 4 5 the variable 34s values of pyrite 3 8 to 4 7 and 18omgt values of magnetite 0 6 to 4 1 suggest that they were not sourced from a single reservoir the hongyuntan magnetite deposit is spatially and temporally associated with volcanism and may be genetically related to it the fluid inclusions and isotopic compositions of this deposit indicate that its ore forming fluid was derived from the exsolution of deep seated magmas and that fluid mixing could have effectively triggered the deposition of ore forming materials multiple periods of volcanic activity could have incorporated additional heat and ore metals into the ore forming system based on our data we conclude that the origin of the hongyuntan magnetite deposit is related to the volcanism in the carboniferous period

the marcona magnetite deposit ica south central peru a product of hydrous iron oxide rich melts marcona the preeminent andean magnetite deposit 1 9 gt 55 4 fe and 0 12 cu is located in the iron oxide copper gold iocg subprovince of littoral south central peru fe oxide and cu zn pb sulfide mineralization was controlled by northeast striking faults transecting a middle jurassic aalenian to oxfordian andesitic shallow marine arc and a succession of contiguous plate boundary parallel late jurassic to mid cretaceous volcanosedimentary basins at marcona hydrothermal activity was initiated in the earliest middle jurassic 161 177 ma by high temperature mg fe metasomatism represented by cummingtonite and phlogopite magnetite assemblages subsequently during the terminal eruptions 156 162 ma of the arc widespread albite marialite alteration na cl metasomatism was followed by the emplacement of an en echelon swarm of massive magnetite ore bodies with subordinate overprinted magnetite sulfide assemblages hosted largely by paleozoic metasilici clastics the magnetite orebodies exhibit abrupt smoothly curving contacts dike like to tubular apophyses and intricate amoeboid interfingering with dacite porphyry intrusions there is no convincing megascopic or microscopic evidence for large scale fe metasomatism associated with the main sulfide poor mineralization the largest 400 mt minas 2 3 4 orebody is interpreted as a bimodal magnetite dacite intrusion comprising commingled immiscible melts generated through the dissolution of metasedimentary quartz in parental andesitic magma oxygen and sulfur stable isotope geothermometry indicates that the evolution at ca 159 ma from magnetite biotite calcic amphibole phlogopite fluorapatite to magnetite phlogopite calcic amphi bole pyrrhotite pyrite assemblages coincided with quenching from above 800 c to below 450 c and the concomitant exsolution of dilute aqueous brines subsequently chalcopyrite pyrite calcite pyrrhotite sphalerite galena assemblages in part metasomatic were deposited from lower temperature 360 c brines the cu poor marcona kiruna type magnetite and cu rich iocg deposits in the district therefore although spatially contiguous represent contrasting ore deposit types the former are interpreted as the product of fe oxide melt coexisting with dacite magma within an andesitic arc which failed during the closure of a back arc basin the weak associated magmatic hydrothermal cu sulfide mineralization at marcona was generated through melt vesiculation and contrasts with the considerably higher grade cu and ag rich orebodies of the major cu rich iocg deposits in the central andes e g la candelaria punta del cobre mantoverde raul condestable and mina justa which were the products of cool oxidized hydrothermal fluids plausibly expelled from the adjacent basins during tectonic inversion

review of geology alteration and origin of iron oxide apatite deposits in the cretaceous ningwu basin lower yangtze river valley eastern china implications for ore genesis and geodynamic setting abstract in the cretaceous ningwu volcano sedimentary basin in the yangtze river valley metallogenic belt eastern china there are three areas with a dense distribution of magnetite or hematite deposits the meishan deposit in the north washan nanshan and taocun deposits in the center and the zhongjiu and gushan deposits in the south the mineralization in the ningwu basin is associated mainly with subvolcanic intrusions consisting of gabbro diorite porphyry and or gabbro diorite alteration zoning of these deposits is pronounced and includes 1 an upper light colored zone of argillic kaolinite silica carbonate and pyritic alteration 2 a middle dark colored zone of diopside fluorapatite magnetite phlogopite and garnet with fluorapatite magnetite 3 a lower light colored zone of extensive albitic alteration however at the gushan iron deposit the lower light colored zone and the middle dark colored zone are absent whereas the principal alteration is represented by silicification kaolinization and carbonatization the iron oxide apatite deposits in the ningwu basin are typically magmatic metasomatic origin and are similar to the kiruna type deposits in scandinavia particularly with respect to mineral assemblages fabric and structure of the iron ores occurrence of the orebodies and wall rock alteration the iron oxide apatite deposits of the ningwu basin contain magnetite and or hematite with diopside or actinolite and apatite gangue they were formed in a rift or extensional environment and the mineralization is associated with alkaline magmatism the time interval between magmatism and related mineralization is very short

geological geochronological and h o isotopic constraints on the genesis of the tongjing cu au deposit in the ningwu basin east china abstract the tongjing cu au deposit is a medium sized deposit within the ningwu volcanic basin east china and is hosted by cretaceous volcanic rocks of the dawangshan and niangniangshan formations the veined and lenticular cu au orebodies are spatially and temporally related to the volcanic and subvolcanic rocks of the niangniangshan formation in the ore district the wall rock alteration is dominated by silicification siderite alteration carbonation sericitization chloritization and kaolinization on the basis of field evidence and petrographic observations two stages of mineralization are recognized 1 a siderite quartz sulfide stage stage 1 associated with the formation of chalcopyrite and pyrite in a quartz and siderite gangue and 2 a quartz bornite stage stage 2 cutting the stage 1 phases stage 1 is the main mineralization stage quartz that formed in stage 1 has 18 o h2o values of 4 3 to 3 5 with d values of fluid inclusion waters of 97 1 to 49 9 indicating that the ore forming fluids were derived from early magmatic fluids and may have experienced oxygen isotopic exchange with meteoric water during stage 1 mineralization la mc icp ms zircon u pb dating of the mineralization related nosean bearing phonolite and nosean bearing phonolitic brecciated tuff at tongjing yields ages of 129 8 0 5 ma and 128 9 1 1 ma respectively these results are interpreted as the crystallization age of the volcanic rocks of the niangniangshan formation a hydrothermal sericite sample associated with cu au mineralization at tongjing yields a plateau 40 ar 39 ar age of 131 3 1 3 ma these results confirm a genetic link between the volcanism and associated cu au mineralization the tongjing cu au deposit in the ningwu basin is genetically and possibly tectonically similar to alkaline intrusion related gold deposits elsewhere in the world

geology and geochronology of magnetite apatite deposits in the ning wu volcanic basin eastern china the ning wu volcanic basin is an important part of the middle lower yangtze river valley metallogenic belt in eastern china where magnetite apatite deposits are common these magnetite apatite deposits can be classified into two types the first type includes the washan taocun heshangqiao and dongshan deposits which are hosted in diorite porphyry and adjacent volcanic rocks the second type includes gushan baixiangshan and hemushan deposits developed at the contact between gabbro diorite and sedimentary rocks we used 40ar 39ar dating on phlogopite and u pb la icp ms dating of zircon in ore related diorite porphyry and gabbro diorite to determine the timing of iron mineralization in the basin the ages of the magnetite apatite deposits such as washan taocun heshangqiao gushan baixiangshan hemushan deposits are from 130 ma to 131 ma thus the magnetite apatite deposits in the ning wu volcanic basin all formed at about 130 ma later than the skarn and porphyry cu au deposits in the adjacent fault uplift areas such as edongnan jiu rui anqing guichi and tongling clusters that are between 146 ma and 135 ma based on available petrological and geochemical data the magnetite apatite deposits in the ning wu volcanic basin are interpreted to have formed under regional lithospheric extension and thinning and ore forming elements were derived from basaltic melts sourced from enriched lithospheric mantle and the crust

an evolving magmatic hydrothermal system in the formation of the mesozoic meishan magnetite apatite deposit in the ningwu volcanic basin eastern china abstract the meishan iron deposit contains 338 mt of iron ore reserves at 39 fe and represents the largest magnetite apatite deposit in the ningwu basin of eastern china controversy has long existed about whether this deposit had a hydrothermal or iron oxide melt origin iron mineralization is genetically related to plutons that are composed of gabbro diorite which were emplaced at 130 1 ma these rocks have sio2 contents of 51 72 54 60 wt na2o contents of 3 47 4 04 wt k2o contents of 2 02 2 69 wt and k2o na2o ratios of 0 51 0 73 these rocks are enriched in liles and lrees and depleted in nb ta and ti which indicates that the magma originated through partial melting of an enriched lithospheric mantle source in a subduction environment a pattern of decreasing initial sr isotopic ratios and increasing end t values with time in early cretaceous magmatic rocks of the ningwu basin may indicate incorporation of increasing proportions of asthenospheric mantle material into the source magma which is consistent with the processes of lithospheric thinning and asthenospheric upwelling in eastern china related to mesozoic subduction of the paleo pacific plate two stages of magnetite are found in the gabbro diorite 1 early crystallized magnetite as euhedral subhedral crystals in larger clinopyroxene crystals and 2 later crystallized magnetite and accompanying ilmenite grains in the voids between plagioclase and clinopyroxene crystals the formation of magnetite before clinopyroxene combined with the results of fe ti oxide geothermometry and analysis of magnetite v content indicates that the oxygen fugacity of the source magma was greater than fmq 2 2 at an early stage 640 c but decreased to fmq 2 66 as abundant magnetite crystallized at a later stage 489 c the early crystallization of magnetite at a high oxygen fugacity does not support a fenner evolution trend for the primitive magma and diminishes the likelihood of liquid immiscibility which could have generated an iron rich melt and is thus inconsistent with an iron oxide melt origin for the meishan iron deposit the 34s values of pyrite 6 6 15 1 and anhydrite 15 6 16 9 in the deposit and the occurrence of evaporites under the volcanic rocks likely indicate that the iron ores and alteration rocks of the meishan deposit were formed by the circulation of fluids of evaporitic origin driven by heat from the hypabyssal gabbro diorite intrusives in the late magmatic stage oxygen fugacity decreased to a reducing range triggering the reduction of sulfate to reduced sulfur and leading to local gold and pyrite mineralization

in situ elemental and isotopic analysis of fluorapatite from the taocun magnetite apatite deposit eastern china constraints on fluid metasomatism metasomatic alteration of fluorapatite has been reported in several iron oxide apatite ioa deposits but its effect on elemental and isotopic variations has not been well understood in this study we present integrated elemental u pb sr and o isotopic microanalytical data on fresh and altered domains in fluorapatite from the taocun ioa deposit eastern china to evaluate the timing and nature of the metasomatism and its effects on the ore forming event orebodies of the taocun deposit are spatially associated with a subvolcanic intermediate intrusion which displays zonal alteration patterns with albite in the center and increasing actinolite chlorite epidote and carbonate toward the margin both disseminated and vein type ores are present in the taocun deposit and fluorapatite commonly occurs with magnetite and actinolite in most ores fluorapatite grains from the both types of ores have been variably metasomatized through a coupled dissolution reprecipitation mechanism many trace elements including na cl s si mg sr u th and rees y were variably leached from the fluorapatite grains during this process and the sr and o isotopic signatures of the grains were also modified the altered fluorapatite grains domains have in situ 87 sr 86 sr ratios 0 70829 0 70971 slightly higher than those of the fresh fluorapatite 0 70777 0 70868 and 18 o values 3 0 to 3 4 variably lower than the primary domains 5 3 to 7 5 the sr and o isotopes of the primary fluorapatite are consistent with or slightly higher than those of the ore hosting intrusion implying that the early stage ore forming fluids were magmatic in origin but underwent weak interaction with the country rocks u pb dating of the fresh and altered domains of the fluorapatite yielded indistinguishable ages of 131 ma which are the same as the age of the ore hosting intrusion in combination with fluid inclusion data we propose that the metasomatism of fluorapatite was induced by hydrothermal fluids at a late stage of the ore forming event the shifts to higher 87 sr 86 sr ratios and lower 18 o values in the altered fluorapatite indicate that the alteration was induced by fluids with more radioactive sr and lighter o isotope signatures the metasomatic fluids were likely dominated by meteoric waters that were mixed with the earlier magmatic fluids and interacted with sedimentary rocks our study highlights that elemental and isotopic compositions of fluorapatite can be significantly modified by hydrothermal fluids during ore forming events thus instead of traditional bulk rock analysis in situ microanalysis is important to provide accurate constraints on the magmatic and or hydrothermal evolution of complex ore forming systems

numerical simulation of debris flows a key requirement in the assessment of landslide risk in such densely populated urban areas as hong kong consists of the prediction of potential runout distance or the extent of the subsequent debris flow this paper presents a three dimensional dynamic model of unsteady gravity driven debris flow the lagrangian galerkin finite element method is used to determine the nodal velocity and depth of soil column elements within the sliding mass with the momentum and mass conservation mathematically closed within the soil column elements the numerical solution also features a lumped mass matrix and a volume weighted procedure the method of least squares approximation plays a smoothing role which enhances stability and efficiency of the numerical solution scheme the nodal elevation during sliding is obtained via a dynamic bilinear interpolation of the elevation function for the base of the sliding mass furthermore the accuracy robustness and generality of this method are validated by experimental results

calculation of oxygen isotope fractionation in metal oxides abstract a theoretical model calculating the thermodynamic isotope factors of oxygen in metal oxides of geochemical interest is presented for temperatures between 0 and 1200 c on the basis of the modified increment method the following order of 18o enrichment is obtained cassiterite rutile magnetite ilmenite ulvospinel hematite uraninite chromite corundum spinel the results are expressed as 103 in a 106 t2 b 103 t c which compare well with existing theoretical experimental and empirical calibrations on quartz oxides and oxides water systems the present calculations enable not only estimation of the oxygen isotope composition of fluids from which the metal oxides were precipitated when independent temperature information is available but can also be applied as oxygen isotope geothermometers to igneous and metamorphic rocks

real time observation of an active debris flow watershed in the wenchuan earthquake area abstract debris flows occur frequently and cause considerable damage in the wenchuan earthquake area however there has been no systematic real time monitoring of such events this study used a monitoring system to consider the spatial variation of meteorological and flow processes in a 39 4 km2 watershed the system comprised three rainfall gauges at different locations and three hydrological monitoring stations located on the mainstream and tributaries with instruments to measure the velocity height and density of debris flows based on the monitoring data the debris flow events were categorized and the general runoff velocity discharge and density were analysed we proposed empirical methods for estimating the velocity and the total volume of debris flows based on other easily obtainable parameters e g maximum flow depth and duration comparison of the results derived using the monitoring data and empirical formulas with those obtained in other small watersheds worldwide revealed the debris flow characteristics in this relatively large watershed rainfall threshold for the debris flows was proposed which is higher than those proposed for the same region for periods shortly after the wenchuan earthquake 2008 2013 and the temporal evolution of the rainfall conditions necessary for debris flows was addressed

rockfall hazard analysis using lidar and spatial modeling abstract rockfalls have been significant geohazards along the canadian class 1 railways cn rail and cp rail since their construction in the late 1800s these rockfalls cause damage to infrastructure interruption of business and environmental impacts and their occurrence varies both spatially and temporally the proactive management of these rockfall hazards requires enabling technologies this paper discusses a hazard assessment strategy for rockfalls along a section of a canadian railway using lidar and spatial modeling lidar provides accurate topographical information of the source area of rockfalls and along their paths spatial modeling was conducted using rockfall analyst a three dimensional extension to gis to determine the characteristics of the rockfalls in terms of travel distance velocity and energy historical rockfall records were used to calibrate the physical characteristics of the rockfall processes the results based on a high resolution digital elevation model from a lidar dataset were compared with those based on a coarse digital elevation model a comprehensive methodology for rockfall hazard assessment is proposed which takes into account the characteristics of source areas the physical processes of rockfalls and the spatial attribution of their frequency and energy

early proterozoic cu au and fe ore deposits associated with regional nacl metasomatism in northern fennoscandia scapolite is widely distributed in 1 9 2 5 ga volcano sedimentary rocks and 1 77 2 2 ga igneous rocks over several hundred square kilometres in northern fennoscandia comprising northern sweden no

late cretaceous early tertiary palaeoclimates of northern high latitudes a quantitative view analyses of plant community structure vegetational and leaf physiognomy and growth rings and vascular systems in wood provide qualitative and quantitative data that can be combined to define non marine palaeoclimatic parameters with better resolution than is available from other principally sedimentological methods application of these techniques to cenomanian through paleocene floras from high palaeolatitudes 75 85 n indicates a polar light regime similar to that of the present plant data suggests cenomanian sea level mean annual air temperatures mats of 10 c and mats of 13 c 5 c and 6 7 c in the coniacian maastrichtian and paleocene respectively evapotranspirational stresses at sea level were low and precipitation was in most part uniform throughout the growing season in the cenomanian with possible seasonal drying occurring by the maastrichtian maastrichtian winter freezing was likely but periglacial conditions did not exist at sea level permanent ice was likely above 1700 m at 75 n in the cenomanian and above 1000 m at 85 n in the maastrichtian these near polar data provide critical constraints on global models of late cretaceous to early tertiary climates

geochemistry petrogenesis and metallogenesis of the panzhihua gabbroic layered intrusion and associated fe ti v oxide deposits sichuan province sw china the panzhihua gabbroic layered intrusion is associated with the 260ma emeishan large igneous province in sw china this sill like body hosts a giant fe ti v oxide deposit with 1333 million ton ore reserves which makes china a major producer of these metals the intrusion has a marginal zone of fine grained hornblende bearing gabbro and olivine gabbro followed upward by lower middle and upper zones the lower and middle zones consist of layered melanogabbro and gabbro composed of cumulate clinopyroxene plagioclase and olivine these zones also contain magnetite layers the upper zone consists chiefly of leucogabbro composed of plagioclase and clinopyroxene with minor olivine most rocks in the body show variable scale rhythmic modal layering in which dark minerals primarily clinopyroxene dominate in the lower parts of each layer and lighter minerals primarily plagioclase dominate in the upper parts the oxide ores occur as layers and lenses within the gabbros and are concentrated in the lower parts of the intrusion ore textures and associated mineral assemblages indicate that the ore bodies formed by very late stage crystallization of v rich titanomagnetite from an immiscible oxide liquid in a fluidrich environment the rocks of the panzhihua intrusion become more evolved in chemistry upward and follow a tholeiitic differentiation trend with enrichment in fe ti and v they are enriched in light rare earth elements relative to heavy rare earth elements and exhibit positive nb ta and ti anomalies and negative zr and hf anomalies the silicate rocks and oxide ores of the panzhihua intrusion formed from highly evolved fe ti v rich ferrobasaltic or ferropicritic magmas the textures of the ores and the abundance of minor hydrous phases indicate that addition of fluids from upper crustal wall rocks induced the separation of the immiscible oxide melts from which the fe ti v oxide ore bodies in the lower part of the intrusion crystallized

petrogenesis of cretaceous adakitic and shoshonitic igneous rocks in the luzong area anhui province eastern china implications for geodynamics and cu au mineralization both adakitic and shoshonitic igneous rocks in the luzong area anhui province eastern china are associated with cretaceous cu au mineralization the shaxi quartz diorite porphyrites exhibit adakite like geochemical features such as light rare earth element lree enrichment heavy ree hree depletion high al2o3 mgo sr sr y and la yb values and low y and yb contents they have low end t values 3 46 to 6 28 and high 87sr 86sr i ratios 0 7051 0 7057 sensitive high resolution ion microprobe shrimp zircon analyses indicate a crystallization age of 136 3 ma for the adakitic rocks most volcanic rocks and the majority of monzonites and syenites in the luzong area are k rich or shoshonitic and were also produced during the cretaceous 140 125 ma they are enriched in lree and large ion lithophile elements and depleted in ti and nb and ba and exhibit relatively lower end t values ranging from 4 65 to 7 03 and relatively higher 87sr 86sr i ratios varying between 0 7057 and 0 7062 the shoshonitic and adakitic rocks in the luzong area have similar pb isotopic compositions 206pb 204pb 17 90 18 83 207pb 204pb 15 45 15 62 and 208pb 204pb 38 07 38 80 geological data from the luzong area suggest that the cretaceous igneous rocks are distributed along ne fault zones e g tanlu and yangtze river fault zones in eastern china and were likely formed in an extensional setting within the yangtze block the shaxi adakitic rocks were probably derived by the partial melting of delaminated lower crust at pressures equivalent to crustal thickness of 50 km i e 1 5 gpa possibly leaving rutile bearing eclogitic residue the shoshonitic magmas in contrast originated mainly from an enriched mantle metasomatized by subducted oceanic sediments they underwent early high pressure 1 5 gpa fractional crystallization at the boundary between thickened 50 km lower crust and lithospheric mantle and late low pressure 1 5 gpa fractional crystallization in the shallow 50 km crust the adakitic and shoshonitic rocks appear to be linked to an intra continental extensional setting where partial melting of enriched mantle and delaminated lower crust was probably controlled by lithospheric thinning and upwelling of hot asthenosphere along ne fault zones e g tanlu and yangtze river fault zones in eastern china both the shoshonitic and adakitic magmas were fertile with respect to cu au mineralization

immiscible silicate liquid partition coefficients implications for crystal melt element partitioning and basalt petrogenesis this study investigates partitioning of ele ments between immiscible aluminosilicate and boro silicate liquids using three synthetic mixtures doped with 32 trace elements in order to get a good spatial separation of immiscible liquids we employed a high temperature centrifuge experiments were performed at 1 050 1 150 c 1 atm in sealed fe and pt containers quenched products were analysed by electron micro probe and la icp ms nernst partition coefficients d s between the fe rich and si rich aluminosilicate immiscible liquids are the highest for zn 3 3 and fe 2 6 and the lowest for rb and k 0 4 0 5 the plots of d values against ionic potential z r in all the composi tions show a convex upward trend which is typical also for element partitioning between immiscible silicate and salt melts the results bear upon the speciation and structural position of elements in multicomponent silicate liquids the ferrobasalt rhyolite liquid immis cibility is observed in evolved basaltic magmas and may play an important role in large gabbroic intrusions such as skaergaard and during the generation of unusual lavas such as ferropicrites

transient deterministic shallow landslide modeling requirements for susceptibility and hazard assessments in a gis framework abstract application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall topography and the distribution and properties of hillside materials we survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore pressure response to rainfall infiltration with an infinite slope stability calculation pore pressures and factors of safety are computed on a cell by cell basis and can be displayed or manipulated in a grid based gis input data are high resolution 1 8 m topographic information derived from lidar data and simple descriptions of initial pore pressure distribution and boundary conditions for a study area north of seattle washington rainfall information is taken from a previously defined empirical rainfall intensity duration threshold and material strength and hydraulic properties were measured both in the field and laboratory results are tested by comparison with a shallow landslide inventory comparison of results with those from static infinite slope stability analyses assuming fixed water table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses moreover results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area

a dynamic model for rainfall induced landslides on natural slopes assessment of landslide hazard often requires a good knowledge of the landslide characteristics and runout mechanics in this paper a quasi three dimensional model using lagrangian finite element method lfem is formulated to reproduce the dynamic runout process caused by landslides a case study of rainfall induced landslide on a natural slope in 1993 in lantau island hong kong is presented voellmy rheology is adopted to characterize the multi dimensional runout behaviour for engineering applications the selection of appropriate rheology and the determination of relevant key parameters associated with the failure mechanisms and runout mechanics are highlighted details of the mathematical formulation particularly with respect to the stability of the numerical scheme and quality control of the mesh are provided the close correlation between the calculation results and the field observations shows that if an appropriate rheological relationship is selected for the simulation a reasonable description of the runout behaviour can be obtained using the present model implications of the potential hazard from natural terrain landslides to downslope development are also discussed used in conjunction with geographical information system gis database the model can also be applied to the preliminary hazard zoning of terrain and land use management in mountainous areas

molybdenite re os and albite 40ar 39ar dating of cu au mo and magnetite porphyry systems in the yangtze river valley and metallogenic implications abstract the area of the middle lower yangtze river valley eastern china extending from wuhan hubei province to western zhenjiang jiangsu province hosts an important belt of cu au mo and fe deposits there are two styles of mineralization i e skarn porphyry stratabound cu au mo fe deposits and magnetite porphyry deposits in several nne trending cretaceous fault bound volcanic basins the origin of both deposit systems is much debated we dated 11 molybdenite samples from five skarn porphyry cu au mo deposits and 5 molybdenite samples from the datuanshan stratabound cu au mo deposit by icp ms re os isotope analysis nine samples from the same set were additionally analyzed by ntims on re os results from the two methods are almost identical the re os model ages of 16 molybdenite samples range from 134 7 2 3 to 143 7 1 6 ma 2 the model ages of the five samples from the datuanshan stratabound deposit vary from 138 0 3 2 to 140 8 2 0 ma with a mean of 139 3 2 6 ma their isochron age is 139 1 2 7 ma with an initial os ratio of 0 7 8 1 mswd 0 29 these data indicate that the porphyry skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system albite 40 ar 39 ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 ma i e 10 20 ma later both mineralization styles characterize transitional geodynamic regimes i e the period around 140 ma when the main ns trending compressional regime changed to an ew trending lithospheric extensional regime and the period of 125 115 ma of dramatic ew trending lithospheric extension

a new paraclupeid fish clupeomorpha ellimmichthyiformes from a muddy marine pro delta environment middle cenomanian dunvegan formation alberta canada a black marine mudstone in allomember a of the middle cenomanian dunvegan formation alberta yielded a well preserved deep bodied fish skeleton attributable to a new genus and species tycheroichthys dunveganensis in the paraclupeidae clupeomorpha ellimmichthyiformes this new taxon appears most closely related to members of the subfamily paraclupeinae which includes largely freshwater and estuarine or marginal marine species known from south and central america and china the dunvegan formation represents a large delta complex deposited in the western interior seaway at about 65 n where mean sea water temperature may have been about 10 c the specimen was found about 60 km from the contemporaneous shoreline and in life apparently inhabited a shallow muddy pro delta environment characterized by high turbidity and variable salinity the fish may have died when it was engulfed by brackish floodwater that also introduced suspended mud that rapidly buried the body preventing physical disarticula

modelling the space time evolution of bed entrainment for flow like landslides abstract the paper discusses the space time evolution of bed entrainment for some typical flow like landslides in three different test areas first the attention is focused on debris avalanches da whose lateral spreading is highly affected by bed entrainment two cases of debris avalanches turning into debris flows df i e channelized flows are then investigated to discuss the potential occurrence of complex bed entrainment scenarios a quasi 3d depth integrated coupled sph smooth particle hydrodynamic model is used the numerical results show that i the eroded thicknesses have maximum values in the intermediate portion of the debris avalanche path and ii the computed time variations of eroded thicknesses and the entrainment rates are consistent with those indicated in recent literature for das at the studied areas in addition the computed scenarios are differentiated in terms of unitary flow discharge identifying the typical behaviour of small volume da landslides propagating inside gullies as dfs and combined dfs and das

new field evidence bearing on the origin of the el laco magnetite deposit northern chile a reply the el laco magnetite deposit has been interpreted as lava flows and feeder dikes formed from iron oxide magma but more recently as a product of metasomatic replacement open pit exposure created at laco sur during the 1990s reveals that the massive magnetite contains magnetite veined blocks and smaller fragments of altered andesitic volcanic rock clearly supporting the replacement origin open space growth of magnetite and pyroxene along the walls of chimney structures and veins within magnetite indicates precipitation from aqueous fluid rather than from gas alone the native sulfur bearing cristobalite alunite alteration widespread at el laco and broadly contemporaneous with magnetite formation is recognized as part of a steam heated horizon generated in the vadose zone above a paleowater table consequently the magnetite replacement must have taken place beneath the paleowater table but probably 300 m beneath the paleosurface thus magnetite deposition at or immediately beneath the paleosurface is precluded the main outstanding question is how hot hypersaline brine the probable ore forming fluid at el laco attained such shallow crustal levels within a high volcanic edifice without undergoing the extensive groundwater dilution documented from most shallowly preserved hydrothermal systems

middle turonian dinosaur paleoenvironments in the upper cretaceous kaskapau formation northeast british columbia the kaskapau formation is a mudstone dominated wedge up to 950 m thick that spans late cenomanian to middle turonian time the formation has a prominent wedge geometry and was deposited in the foredeep of the western canada foreland basin in outcrop in northeast british columbia nearshore sandstones are locally well developed and include rare wedges of nonmarine strata on quality creek near tumbler ridge 11 m of nonmarine strata contain abundant dinosaur tracks and the first in situ dinosaur bone reported from british columbia this site at a paleolatitude of about 67 n preserves a rare glimpse of turonian terrestrial environments during global eustatic highstand three main dinosaur habitats are recognized strandplain and beach ridge freshwater lake and brackish lagoon back beach sandstone has a relief of about 2 5 m interpreted as beach ridges sandy coals containing abundant dinosaur tracks represent inter ridge slough deposits overlying lake deposits comprising laminated muds with freshwa

a model for the runout analysis of rapid flow slides debris flows and avalanches runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows debris avalanches rockslide avalanches large scale liquefaction failure

alteration oxygen isotope and fluid inclusion study of the meishan iron oxide apatite deposit se china the meishan deposit 338 mt at 39 fe comprises massive ores in the main orebody and stockwork and disseminated ores along the main orebody four stages of mineralization and related alteration have been identified the second stage of mineralization which was the main stage of iron mineralization formed stringer disseminated iron ores as well as the main meishan orebody the fourth stage formed small pyrite and or gold orebodies above or alongside the main magnetite orebody stage 2 apatites have homogenization temperatures of 257 485 c and salinities of 7 3 11 wt nacleq calculated 18ofluid values of magnetite and apatite from the disseminated ores vary between 7 7 and 14 9 which is similar to values observed in the massive ores 8 1 12 9 the high 18o fluids at meishan have been interpreted as being of magmatic hydrothermal origin these fluids are indicative of the boiling of ore forming fluids quartz occurring as cavity fillings gives homogenization temperatures from 202 to 344 c with most values lying between 250 and 330 c corresponding salinities are 5 wt nacleq calculated 18ofluid values are 6 4 to 6 8 these values indicate that the lower temperature 250 330 c quartz was deposited from a cooling magmatic hydrothermal fluid stage 3 siderites contain fluid inclusions that homogenized between 190 and 310 c mainly between 210 and 290 c corresponding salinities are 4 8 wt nacleq stage 4 quartz carbonate veinlets contain fluid inclusions that homogenized at moderate to low temperatures 150 230 c and exhibit low salinities 2 10 wt nacl eq 18ofluid values of the mineralizing fluids for the quartz and calcite can be calculated to vary from 0 7 to 5 6 and 6 3 to 10 2 respectively while there is some overlap the 18o values of the fluids are generally lower than those observed in the massive and disseminated magnetite ores d values for the quartz and calcite vary between 154 and 123 and 123 and 111 respectively these values suggest late stage input of a shallow sourced isotopically light meteoric fluid at the temperature of pyrite and gold deposition the fluid inclusion and stable isotope data indicate a cooling magmatic hydrothermal system that progressed from isotopically heavy to isotopically depleted fluids as it cooled such fluid evolution is comparable with those of other kiruna type deposits worldwide

mineralogy and geochemistry of fe ti oxide and apatite nelsonite deposits and evaluation of the liquid immiscibility hypothesis modal mineralogy determined for 32 fe ti oxide and apatite rocks from localities in virginia new york quebec norway and sweden largely supports the 2 1 oxide apatite ratio suggested as a eutectic mixture by philpotts 1967 a fairly consistent suite of accessory minerals including biotite clinoamphibole spinel zircon and sulfides is present some silicate accessory minerals tend to form glomeroporphyritic intergrowths in an equigranular matrix of nelsonite suggesting that the accessories are xenocrysts that have been trapped in an oxide apatite liquid this liquid may represent an extreme case of partitioning of high charge density cations into a low silica phosphorus enriched immiscible melt temperature and oxygen fugacity estimates for oxide pairs in nelsonites range from 600 degrees to 1 000 degrees c and 10 super 20 to 10 super 11 atm f sub o 2 and bracket an equilibration path that is close to the fmq buffer curve several stages of exsolution are evident in fe ti oxides of some deposits nelsonites contain fluorapatite that is enriched in light lanthanides the occurrence of nelsonite dikes in roseland anorthosite and associated rocks of the roseland piney river district of virginia is explained by the infilling of fractures with nelsonite liquid that has settled out of an overlying ferrodiorite pluton

fluid inclusion and stable isotope study of the esfordi apatite magnetite deposit central iran a reply sir we are pleased that our recent paper in economic geology jami et al 2007 presenting the geologic setting a description of the mineralization fluid inclusion and o isotope analyses of the esfordi p fe oxide deposit in central iran has been of interest to aftabi and his colleagues aftabi et al 2009 the opportunity to discuss further some aspects of our paper is appreciated including support for a hydrothermal dominated depositional model for esfordi aftabi et al 2009 focus their comments on the question of the affinity of the esfordi p fe oxide deposit in particular they argue that esfordi and by inference other diverse fe oxide deposits within the bafq district of central iran should be considered rapitan type banded iron formations i e bif klein 2005 rather than kiruna type hitzman 2000 in discussing our results and conclusions in the light of previous work particularly forster and jafarzadeh 1994 aftabi et al 2009 have misconstrued our interpretation of some of the textural and isotopic data as providing support for an orthomagmatic model for the esfordi p fe oxide deposit based on the structure relationships between mineralization and host rocks fluid inclusion and isotopic data we concluded that esfordi exhibits strong evidence of hydrothermal origin though we did not preclude some component of precursor orthomagmatic processes in formation of the p fe mineralisation it is noted that some examples of the kiruna end member of the continuum of fe oxide deposits discussed by hitzman 2000 are controversial particularly in regard to their evolution sillitoe and burrows 2002 henriquez et al 2003 we have shown that esfordi has a number of features typical of the kiruna type deposits and does not exhibit features consistent with an affinity to rapitan type fe oxide deposits this evidence will be discussed briefly with further data

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

a sph depth integrated model for popocatepetl 2001 lahar mexico sensitivity analysis and runout simulation abstract lahars are debris flows of volcanic origin which can endanger or even destroy communities located near the flanks of volcanoes lahars are not always triggered by eruptions they can form during heavy rainfall or after hydrothermal alteration and volcanic edifice collapse decision makers need lahar hazard maps to devise hazard prevention measures that will prevent casualties so lahar modelling is an important tool for assessing flow behavior and determining inundation areas the depth integrated numerical model used in this study is derived from the velocity pressure of the biot zienkiewicz model and was discretized using the smoothed particle hydrodynamics sph method to simulate a lahar that occurred at popocatepetl volcano in 2001 in order to investigate the convergence of the model we used a range of different sph mesh resolutions once the optimum mesh resolution was bounded we analyzed the model s sensitivity to the initial lahar volume the density of the geomaterial and the rheological parameter of the bingham fluid the results show that the sph depth integrated model produced a highly accurate simulation of the distribution and velocity of the 2001 lahar the study also shows the effects of sph mesh resolution and the relevant influence of rheological parameters

evaluation of approaches to calculate debris flow parameters for hazard assessment abstract many different runout prediction methods can be applied to estimate the mobility of future debris flows during hazard assessment the present article reviews the empirical analytical simple flow routing and numerical techniques all these techniques were applied to back calculate a debris flow which occurred in 1982 at la guingueta catchment in the eastern pyrenees a sensitivity analysis of input parameters was carried out while special attention was paid to the influence of rheological parameters we used the voellmy fluid rheology for our analytical and numerical modelling since this flow resistance law coincided best with field observations the simulation results indicated that the basal friction coefficients rather affect the runout distance while the turbulence terms mainly influence flow velocity a comparison of the velocity computed on the fan showed that the analytical model calculated values similar to the numerical ones the values of our rheological parameters calibrated at la guingueta agree with data back calculated for other debris flows empirical relationships represent another method to estimate total runout distance the results confirmed that they contain an important uncertainty and they are strictly valid only for the conditions which were the basis for their development with regards to the simple flow routing algorithm this methods could satisfactorily simulate the total area affected by the 1982 debris flow but it was not able to directly calculate total runout distance and velocity finally a suggestion on how different runout prediction methods can be applied to generate debris flow hazard maps is presented taking into account the definition of hazard and intensity the best choice would be to divide the resulting hazard maps into two types final hazard maps and preliminary hazard maps only the use of numerical models provided final hazard maps because they could incorporate different event magnitudes and they supplied output values for intensity calculation in contrast empirical relationships and flow routing algorithms or a combination of both could be applied to create preliminary hazard maps the present study only focussed on runout prediction methods other necessary tasks to complete the hazard assessment can be looked up in the guidelines for landslide susceptibility hazard and risk zoning included in this special issue

mineralogy fluid inclusion petrography and stable isotope geochemistry of pb zn ag veins at the shizhuyuan deposit hunan province southeastern china the shizhuyuan polymetallic deposit is located in the central part of the nanling region southeastern china and consists of proximal w sn mo bi skarns and greisens and distal pb zn ag veins the sulfides and sulfosalts in the distal veins formed in three distinct stages 1 an early stage of pyrite and arsenopyrite 2 a middle stage of sphalerite and chalcopyrite and 3 a late stage of galena ag sn and bi bearing sulfides and sulfosalts and pyrrhotite combined sulfide and sulfosalt geothermometry and fluid inclusion analyses indicate that the early stage of mineralization occurred at a temperature of 400 c and involved boiling under hydrostatic pressure 200 bar with the temperature of the system dropping during the late stage to 200 c laser raman analysis indicates that the fluid inclusions within the studied minerals are dominated by h2o although some contain carbonate solids and ch4 gas vein hosted sulfides have 34s values of 3 8 6 3 that are interpreted as indicative of a magmatic source of sulfur the mineralization process can be summarized as follows an aqueous fluid exsolved on final crystallization of the qianlishan pluton ascended along fracture zones cooled to 400 c and boiled under hydrostatic conditions and with decreasing temperature and sulfur fugacity sulfide and sulfosalt minerals precipitated successively from the ag cu zn fe pb sb as s bearing fluid system

cretaceous cu au pyrite and fe oxide apatite deposits in the ningwu basin lower yangtze area eastern china abstract the cretaceous ningwu volcanic basin of the middle and lower yangtze river valley metallogenic belt of eastern china hosts numerous fe oxide apatite cu au and pyrite deposits the mineralization in the ningwu basin is associated with subvolcanic rocks consisting of gabbro diorite porphyry and or pyroxene diorite however the mineralization is associated with subvolcanic and volcanic rock suite belonging to the niangniangshan formation in the tongjing cu au deposit including nosean bearing aegirine augite syenites quartz syenites and quartz monzonites the zoning displayed by the alteration and mineralization comprises 1 an upper light colored zone of argillic carbonate and pyrite alteration and silicification that is locally associated with pyrite and gold mineralization 2 a central dark colored zone of diopside fluorapatite magnetite phlogopite and garnet alteration associated with fluorapatite magnetite mineralization and 3 a lowermost light colored zone of extensive albite alteration the cu au and pyrite orebodies are peripheral to the fe oxide apatite deposits in this area and overlie the iron orebodies including the meishan cu au deposit in the northern ningwu basin and the pyrite deposits in the central ningwu basin the 34 s values of sulfides from the fe oxide apatite cu au and pyrite deposits in the ningwu basin show large variation with a mixed sulfur source including magmatic sulfur and or a mixture of sulfur derived from a magmatic component country rock and thermochemical reduction of sulfate at 200 300 c the ore forming fluids associated with iron mineralization were derived mainly from magmatic fluids and the late stage ore forming fluids related to cu au and pyrite mineralization may have formed by the introduction of cooler meteoric water to the system the fe oxide apatite cu au and pyrite deposits of the ningwu basin formed in an extensional environment and are associated with a large scale magmatic hydrothermal system

albite rich silica depleted metasomatic rocks at emuford northeast queensland mineralogical geochemical and fluid inclusion constraints on hydrothermal evolution and tin mineralization late paleozoic fluorine rich granites and their host metasediments in the emuford district of the herberton tin field contain small zones of intense albitization that host cassiterite mineralization sodium metasomatism was accompanied by hydrothermal leaching of granite quartz to form vuggy albite rocks episyenites vugs created by quartz dissolution were filled in by hydrothermal minerals including albite k feldspar and or muscovite and cassiterite late phases are dominated by quartz and fluorite swarms of parallel veinlets crosscut the albitized zones these veinlets were formed by repeated fracturing in response to local fluid over pressures they contain infill mineralogy similar to the vugs and probably formed at least partly contemporaneously with vug infill due to the overprinting at various scales of alteration vug infill and vein formation stages chemical changes associated with episyenite formation are only qualitatively constrained however the mineralogical and textural features of the alteration zones suggest that most major and trace elements had substantial mobility during their formation major chemical changes associated with episyenite formation include leaching of sio 2 k 2 o rb and ba with introduction of na 2 o and minor sr during vug and vein filling stages there was an introduction of sio 2 al 2 o 3 na 2 o k 2 o cao f and sn the erratic behavior of ree is probably related to the growth of fluorite and minor accessory phases zircon monazite xenotime with preferential enrichment of heavy ree in rocks with the highest fluorine concentrations fluid inclusion study indicates that vug and vein filling stages of the hydrothermal evolution involved two types of fluids a high salinity fluid 30 50 equiv wt nacl of probable magmatic origin and homogenization temperatures up to 428 degrees c was associated with vug filling in the granite hosted deposits a lower salinity fluid 5 15 equiv wt nacl containing variable amounts of co 2 and having homogenization temperatures between 160 degrees and 420 degrees c was associated with veinlet formation in the granite hosted deposits and with vein and cavity filling in the metasediment hosted deposit this lower salinity fluid may represent a condensed vapor phase derived from boiling of the magmatic fluid or may be a mixture of magmatic and meteoric components the close association of albitization and quartz dissolution suggests a genetic link between the two processes it is proposed that exchange of na for k in the fluorine rich hydrothermal fluids caused a substantial increase in quartz solubility and led to quartz dissolution in the albitized rocks

gushan magnetite apatite deposit in the ningwu basin lower yangtze river valley se china hydrothermal or kiruna type abstract the gushan deposit is one of the typical magnetite apatite deposits associated with dioritic porphyries in the lower yangtze river valley belt of the eastern yangtze craton the origin of this deposit is still uncertain and remains a controversial issue divergent opinions are centered on whether the iron deposits are magmatic or hydrothermal in origin however our field observations and mineralogical studies combined with previous published petrological and geochemical features strongly suggest that the main ore bodies in the gushan magnetite apatite deposit are magmatic specific evidence includes the existence of gas bubbles tubes and miarolitic and amygdaloidal structures melt flow banding structure and the presence of ore breccia new electron microprobe analyses of the pyroxene phenocrysts of the dioritic porphyry genetically associated with the gushan magnetite apatite deposit show that the fe contents in the evolving magma dramatically decrease and then gradually increase because there is no evidence of mafic magma recharge this scenario decreasing fe could be plausibly interpreted by fe rich melts separated from fe poor silicate melts i e liquid immiscibility was triggered by minor addition of phosphorus by crustal contamination the occurrence of massive iron ore bodies can be satisfactorily explained by the immiscible fe rich melt with enormous volatile contents was driven to the top of the magma chamber due to the low density the hot and volatile rich iron ore magma was injected along fractures and spaces between the dioritic intrusions and wall rocks and led to an explosion near the surface resulting in the immediate fragmentation of the roof of the intrusion and wall rocks forming brecciated ores moreover other types of ores can be considered as a result of post magmatic hydrothermal activities our proposed metallogenic model involving the kiruna type mineralization is consistent with the observed phenomenon in the gushan deposit

the origin of magnetite apatite rocks of mushgai khudag complex south mongolia mineral chemistry and studies of melt and fluid inclusions abstract the concentration and redistribution of ore components from a primary melt to hydrothermal fluids are important for understanding ore formation the mushgai khudag complex is a typical example of an intrusion where hydrothermal processes are widespread and where we can observe the redistribution of ore components during hydrothermal processes in this study we use mineralogical melt and fluid inclusion data to trace element characteristics of apatite from the mushgai khudag complex to reconstruct the formation of the magnetite apatite rocks and their magmatic hydrothermal evolution and to clarify the origin of the ree mineralization we conclude that the magnetite apatite rocks crystallized from salt melt with a high content of phosphate and sulfate components at a temperature of approximately 830 850 c the origin of magnetite apatite rocks probably can be explained by the silicate salt immiscibility that occurred at the alkaline syenite crystallization stage further evolution of the salt melt to the brine of the carbonate fluoride chloride sulfate composition was accompanied by the barite celestite and monazite ce formation at the temperature of approximately 500 580 c the dissolution of apatite and the crystallization of gypsum phosphosiderite and monazite ce pseudomorphs after apatite took place at the hydrothermal stage after a reaction with a fluid that evolved from carbonate chloride sulfate at 250 350 c into a predominantly chloride composition at 150 250 c the high activity of the sulfate component and a significant enrichment of the rocks in ree also occurred at the late hydrothermal stage

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

fossil crocodilians as indicators of late cretaceous and cenozoic climates implications for using palaeontological data in reconstructing palaeoclimate abstract that the earth s climate has cooled over the last 100 million years has been recognized since the early nineteenth century the transition from the hot house world of the cretaceous a time interval without significant polar icesheets to the ice house world in which we now live today the dynamics process responsible for this change are being examined using computer models especially general circulation models gcm s through such work our understanding of the dynamics of the earth system improves and our ability to predict future trends is enhanced but the success of modelling experiments can only be assessed by comparing results with observations the pattern which for palaeoclimate are drawn exclusively from the geological record palaeoclimate interpreted from geological data is invariably based on analogy with the recent the validity of which depends on corroboration from multiple lines of evidence this requires the compilation and investigation of large global datasets of well constrained geological climate proxies this study uses the palaeodistribution of fossil crocodilians to examine the spatial distribution of palaeoclimate during this transition fossil crocodilians have a relatively good fossil record and are climatically limited in the recent they also provide a manageable global dataset with which to investigate other issues that impinge on the use of geologic data for reconstructing palaeoclimate taphonomy sampling effects time averaging tectonics and for fossils palaeobiogeography and evolution as such this study provides a possible template for examining other climate proxies in order to validate and hone palaeoclimatic interpretations an analysis of modern crocodilians indicates that temperature is the principal influence on their global distribution with the coldest month mean temperature cmm of 5 5 c marking the minimum thermal limit for the group corresponding today to a minimum mean annual temperature mat of 14 2 c the duration of warmth during the year partly indicated by the mean annual range of temperature mart is also important as this affects early juvenile development and survival the presence of standing water provides an essential thermal buffer against temperature extremes by analogy the palaeodistribution of fossil crocodilians suggests the following during the late cretaceous and early palaeogene mat s in excess of 14 2 c cmm s 5 5 c permeated throughout mid latitudes and coastal regions in high latitudes during the oligocene the restriction of fossil crocodilians to low latitudes suggests high latitude cooling as indicated by numerous other lines of evidence coeval restriction of crocodilians to coastal regions in mid latitude north america and much of asia consistent with increased seasonality and aridification in continental interiors may reflect local orographic changes as well as global climate change during the miocene fossil crocodilians return to the great plains of north america but do not reoccupy the continental interior of asia by the pliocene crocodilians are again restricted to low latitudes and coastal regions in mid latitudes coincident with further high latitude cooling and aridification and cooling of mid latitude continental interiors minor distributional changes during the holocene may reflect human effects

large scale stratigraphic architecture eustatic variation and unsteady tectonism a theoretical evaluation we incorporate a process based depositional model with basin subsidence models to predict stratigraphic records this allows us to investigate the importance of subsidence geometry on coastal stratigraphy and thus to characterize and compare the stratigraphic architecture of two categories of tectonic basins the models demonstrate that the correlation of stratigraphic sequences to eustatic cycles is not the same in passive margin basins as in foreland basins and that in a foreland basin the record of episodic tectonism is distinct from that of eustatic sea level change in the model sediment transport is approximated by slope controlled diffusion nonmarine transport is treated as more efficient diffusion than marine transport three different subsidence and sediment supply models are examined a simple passive margin basin a simple foreland basin and then a foreland basin for which vertical motions are driven by thrust shortening that is compensated flexurally and for which sediment supply is related to relief predicted passive margin stratigraphies for cases of varying eustatic sea level are similar to those of natural basins and include progradational packages and subaerial unconformities which are used to define sequence boundaries that form during sea level fall we explore the timing relationships between stratigraphic features and a sinusoidal sea level history showing that the phase relationship depends on subsidence sediment flux efficiency of sediment transport and period and amplitude of sea level when the basic geometry of the basin is inverted placing the sediment supply on the side with maximum subsidence as is the case in foreland basins the sequence character changes markedly subaerial erosion does not generate unconformities in the models of a dynamic foreland basin sediment supply and subsidence are linked to the structure of the flanking thrust belt and are not necessarily constant for steady thrusting and variable sea level unconformities that define sequence boundaries form only on the distal or forebulge side of the basin and the ages of the sequence boundaries correlate to limes of rising sea level in cases of constant sea level but variable thrusting subaerial unconformities are cut locally on both the proximal margin of the basin and the distal margin of the basin yet the ages of the proximal margin and distal margin unconformities are out of phase in the tectonic cycle erosion is most pronounced during quiescence on the proximal side and during thrusting on the distal side

geology alteration age and origin of iron oxide apatite deposits in upper eocene quartz monzonite zanjan district nw iran iron oxide apatite deposits are present in upper eocene pyroxene quartz monzonitic rocks of the zanjan district northwestern iran mineralization occurred in five stages 1 deposition of disseminated magnetite and apatite in the host rock 2 mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks 3 deposition of sulfide ores together with potassic alteration 4 formation of quartz and carbonate veins and sericite chlorite epidote silica carbonate and tourmaline alteration and 5 supergene alteration and weathering u pb dating of monazite inclusions in the apatite indicates an age of 39 99 0 24 ma which is nearly coeval with the time of emplacement of the host quartz monzonite supporting the genetic connection fluid inclusions in the apatite have homogenization temperatures of about 300 c and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids late stage quartz resulted from the introduction of a cooler less saline and isotopically depleted fluid the iron oxide apatite deposits in the tarom area of the zanjan district are typical of a magmatic hydrothermal origin and are similar to the kiruna type deposits with respect to mineral assemblages fabric and structure of the iron ores occurrence of the ore bodies and wall rock alteration

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

evaporitic source model for igneous related fe oxide ree cu au u mineralization we propose that many igneous related fe oxide rich ree cu au u bearing deposits form by hydrothermal processes involving evaporitic ligand sources either coeval salars or older evaporites these deposits are abundant in both phanerozoic and proterozoic extensional continental and continent margin settings they commonly form in global arid zones but they also occur where magmatism is superimposed upon older evaporites magmatic compositions exert only second order control mainly on alteration mineralogy and on element abundances hot s poor brines generated by interaction with evaporitic materials are consistent with geologic settings and help rationalize the distinctive element enrichments siderophile lithophile and hydrothermal alteration sodic locally alkaline found in these systems this model contrasts with immiscible oxide melt and magmatic hydrothermal origins commonly proposed for these deposits although all three mechanisms can occur 31 refs 3 figs 1 tab

ore formation at the washan iron oxide apatite deposit in the ningwu ore district eastern china insights from in situ la icp ms magnetite trace element geochemistry abstract iron oxide apatite ioa deposits are an important type of iron deposit that may host large reserves of iron and other elements the washan deposit in the ningwu ore district is a classic giant ioa deposit hosted by porphyritic diorite at washan four fe mineralization stages have been identified with clear crosscutting relationships forming four types of ores disseminated ores breccia ores and magnetite actinolite and magnetite apatite actinolite veins trace element concentrations and single grain geochemical profiles of magnetite from the four fe mineralization stages were obtained via laser ablation inductively coupled plasma mass spectrometry la icp ms the geochemical profiles show consistent ti v mg and al contents from cores to rims indicating that magnetite might have crystallized quickly under relatively stable conditions in each stage compatible element e g co v ni and cr contents of the washan magnetite are similar to those of magmatic fe ti v deposits with high v and ti contents indicating a close magmatic link increasing mg al mn ni and ga contents and decreasing cr content from early to late stages imply increasingly intense reactions between fe bearing fluids and country rocks e g diorite and evaporites which also suggests a magmatic hydrothermal origin we propose a new genetic model for ore formation at the washan ioa deposit first an fe rich liquid which may have formed via liquid immiscibility ascended through the magma system resulting in the disseminated ores and albite alteration in the porphyritic diorite with cooling and crystallization of the magma the intrusive rocks developed fractures and brecciation which may have provided pathways for fe bearing fluids after the breccia or massive ores formed the pathways would have been quickly sealed by mineral precipitation continuous liquid immiscibility and magma crystallization may have produced similar fluids with more sedimentary material involved and its markers displayed when the fluid pressure overcame the lithostatic pressure the fractures that developed may have provided the necessary conduits for emplacement of the magnetite actinolite and magnetite actinolite apatite veins subsequently the magmatic hydrothermal system might have remained active during cooling and differentiation while pyrite quartz and calcite veins formed

investigation on mineralogy geochemistry and fluid inclusions of the goushti hydrothermal magnetite deposit fars province sw iran a comparison with iocgs abstract the goushti iron deposit from dehbid area located in the sanandaj sirjan metamorphic belt ssb sw iran is hosted by the early mesozoic silicified dolomite mineralized zones are lithostructurally controlled and oriented nw se parallel to the zagros orogenic belt zob magnetite the major ore mineral occurs as open space fillings and is accompanied by the secondary mineral phases hematite goethite and martite gangue minerals mainly include quartz dolomite and k feldspar are associated with minor hydrosilicates calc silicates such as wollastonite and diopside minerals typical of skarns are virtually absent from the ore zones fe2o3 content in the mineralized zones varies in the range of 38 75 wt the concentrations of au cu p ti cr and v as well as co ni cr v lree hree eu sm and la lu values and eu ce anomalies of the studied ores indicate that the goushti deposit is a hydrothermal magnetite type the subvolcanic rhyolite and basalt in this area are regarded as the source of iron and heat in the mineralizing system the fluid inclusion data showed that magnetite deposited from the ore bearing fluid with salinities 1 7 wt nacl equivalent at temperatures of 130 200 c a decrease in temperature and pressure supplemented by fluid mixing is the major controlling factor in iron oxide precipitation the field relationships and mineralogical geochemical characteristics of iron ores indicate that the goushti hydrothermal deposit could not be classified as a member of the iocg iron oxide copper gold deposits

simulation of interactions between debris flow and check dams on three dimensional terrain abstract debris flows are rapid gravity driven flows of sediment water mixture which can be greatly destructive due to its huge volume high velocity and large impact force check dam is essential protective structure for controlling debris flow however it is a challenging work to assess the interactions between debris flow and check dam especially when involving complex topography and dam destruction a numerical method was developed in this study to investigate the interactions between debris flow and check dam on three dimensional terrain the debris flow and check dam were simulated by smoothed particle hydrodynamics sph method and finite element method fem respectively the method was validated by a dam break problem and a granular flow flume test an actual debris flow event originated from failure of tailings dams on 19 july 1985 in stava italy was simulated as an example the results indicate that the proposed method is a practical tool to simulate the runout characteristics of debris flow e g flow velocity flow depth impact area and interactions between debris flow and check dam e g impact force destruction of check dam interception by check dam given similar total dam volume increasing the number of dams will improve the hazard mitigation effect moreover it is recommended to construct dams in downstream area with straight channel this study will contribute to a better understanding of the flow structure interaction and is helpful for rational design of check dams

the hypermobility of huge landslides and avalanches abstract catastrophic failure of large land masses which generate landslides rockfalls and debris avalanches can have hazardous consequences extending far beyond the source observations show that the mobility of such events depends strongly on the volume for volumes larger than 10 6 m 3 with many different processes invoked to explain higher mobilities hypermobility for both terrestrial and extraterrestrial events although the mobility of large events has been extensively studied there is no generally accepted mechanism for predicting extreme travel distances because the underlying physical processes are poorly understood here we show using physical and rheological arguments that the wide scatter observed for very large mass wasting events in all environments collapses to a single relationship between event volume or inundation area and mobility hypermobility is defined to be the reciprocal of the effective friction coefficient e where the scale dependent e is derived analytically as a function of the mechanical volumetric and topographical parameters of the flow the dominant term in the coefficient is the degree of fluidization involved in the flow our results show that fluidization is limited in extraterrestrial events that significant fluidization occurs in non volcanic and volcanic events and fluidization dominates submarine events this analysis demonstrates that fluidization is associated with long run out distances and that the degree of fluidization can be predicted by the volume and physical and topographic parameters the methodology is simple physically based and validated with datasets of very large terrestrial and extraterrestrial avalanche events we demonstrate that the effective coulomb friction rheology and the hypermobility function are applicable to avalanche events of any size providing an opportunity to simulate past and or potential huge landslide and debris avalanche events run out distances destructive impact and assessment of risk the model can be used to estimate the overrun area and volume in terms of known mobility data

sodic calcic alteration in fe oxide cu au districts an origin via unmixing of magmatic h 2 o co 2 nacl cacl 2 kcl fluids iron oxide cu au deposits particularly those formed in deeper level plutonic environments are commonly characterized by regional scale sodic calcic alteration which typically formed pre or syn cu au mineralization the sodic calcic assemblages include albite scapolite pyroxene actinolite apatite titanite epidote and calcite the consistent presence of coexisting hypersaline aqueous and co2 rich fluids in minerals from sodic calcic alteration and associated fe oxide cu au deposits is the result of unmixing of h2o co2 nacl cacl2 kcl magmatic fluids experimental evidence indicates that the na na k ratio of fluids in equilibrium with two alkali feldspars in co3 2 bearing parent fluids would be significantly higher than in unmixed chloride bearing aqueous fluids therefore fluid unmixing caused by decreases in temperature and or pressure will result in albitization of wall rocks as is observed in most deeper level fe oxide cu au deposits this alteration style may be succeeded by k feldspathization with decreasing temperature because of the increase in equilibrium na na k in chloride bearing fluids buffered by alkali feldspars

floodplain palaeosols of the cenomanian dunvegan formation alberta and british columbia canada micromorphology pedogenic processes and palaeoenvironmental implications

neodymium isotopic study of rare earth element sources and mobility in hydrothermal fe oxide fe p ree systems rare earth element ree enriched igneous related hydrothermal fe oxide hosted fe p ree systems from four areas in north america have been analyzed for their neodymium iosotopic composition to constrain ree sources and mobility in these systems the nd isotopic results evidence a common pattern of ree concentration from igneous sources despite large differences in age proterozoic to tertiary tectonic setting subduction vs intraplate and magmatic style mafic vs felsic in the middle proterozoic st francois mountains terrane of southeastern missouri epsilon sub nd for fe p ree apatite monazite xenotime deposits ranges from 3 5 to 5 1 similar to associated felsic to intermediate igneous rocks of the same age epsilon sub nd 2 6 to 6 2 at the mid jurassic humboldt mafic complex in western nevada epsilon sub nd for fe p ree apatite mineralization varies between 1 1 and 2 4 similar to associated mafic igneous rocks minus 1 0 to 3 5 in the nearby cortez mountains in central nevada mid jurassic felsic volcanic and plutonic rocks epsilon sub nd minus 2 0 to minus 4 4 are associated with fe p ree apatite monazite mineralization having similar epsilon sub nd minus 1 7 to minus 2 4 at cerro de mercado durango mexico all assemblages analyzed in this tertiary rhyolite hosted fe oxide deposit have identical isotopic compositions with epsilon sub nd minus 2 5 these data are consistent with coevalmore igneous host rocks being the primary source of ree in all four regions and are inconsistent with a significant contribution of ree from other sources interpretations of the origin of these hydrothermal systems and their concomitant ree mobility must account for nonspecialized igneous sources and varied tectonic settings less

differentiation of nelsonitic magmas in the formation of the 1 74 ga damiao fe ti p ore deposit north china the 1 74 ga damiao anorthosite complex north china is composed of anorthosite and leuconorite with subordinate melanorite mangerite oxide apatite gabbronorite perthite noritic i e jotunitic and ferrodioritic dykes the complex hosts abundant vein pod and lens like fe ti p ores containing variable amounts of apatite 10 60 modal and fe ti oxides in addition to fe ti p ores there are also abundant fe ti ores which are closely associated with fe ti p ores in the deposit most of fe ti p ores are dominated by fe ti oxides and apatite devoid of silicate minerals mineralogically similar to the common nelsonites elsewhere in contrast fe ti ores are dominated by fe ti oxides with minor apatite 5 modal the parental magma of these ores estimated from olivine and apatite compositions using mineral melt partition coefficients has composition similar to the ferrodioritic dykes fe ti p ores have variable fe ti oxides and apatite proportions indicating that they are cumulates their simple assemblage of fe ti oxides and apatite and local net texture suggest that the fe ti p ores in damiao have formed from nelsonitic melts immiscibly separated from the ferrodioritic magma during late stage differentiation fe ti ores are also cumulates and have mineral compositions similar to fe ti p ores the close association between fe ti and fe ti p ores indicates that the fe ti ores may have also formed from the nelsonitic melts we proposed that differentiation of nelsonitic melts accompanied by gravity settling is responsible for the formation of fe ti and fe ti p ores such a differentiation process in nelsonitic melts is well supported by variations of sr y th u ree and eu eu of apatite in fe ti p ores using oxides apatite ratio of 2 1 and compositions of apatite and calculated primary oxides we estimate the composition of the nelsonitic melt as 52 0 wt fe2o3t 18 5 wt cao 14 2 wt p2o5 8 7 wt tio2 4 0 wt al2o3 and 1 1 wt mgo with minor sio2 k2o na2o and f such a nelsonitic melt is suggested to be possibly conjugated with si rich melts compositionally similar to the damiao jotunitic dykes 50 wt sio2 and 15 wt fe2o3t which may subsequently evolve to mangeritic rocks in damiao our modeling also indicates that the onset of immiscibility occurs at a time when the evolved melt has 44 wt sio2 21 wt fe2o3t 3 0 wt tio2 and 2 6 wt p2o5 high oxygen fugacity and phosphorous content in magmas may play important roles in the immiscibility of nelsonitic magmas including promoting iron enrichments and widening the two liquid field