magmatic anhydrite in plutonic rocks at the el teniente cu mo deposit chile and the role of sulfur and copper rich magmas in its formation anhydrite occurs along with biotite feldspars quartz fe oxides and sulfides in fine grained igneous rocks that form the small porphyry a stock at el teniente these minerals crystallized together in the space generated by the intrusion of this stock and they do not replace preexisting phases planar crystal boundaries between anhydrite and other phases as well as the fact that plagioclase and biotite are fresh and unaltered also suggest that anhydrite is an igneous phase and not the product of secondary hydrothermal alteration plagioclase is unusually na rich ranging from oligoclase in mafic varieties of these rocks with 20 percent biotite to albite in more felsic samples with 20 percent these unusual anhydrite bearing plutonic rocks which contain up to 3 wt percent s and 0 5 wt percent cu are isotopically similar to all other igneous rocks related to the deposit these rocks formed during a late miocene period of regional compressive deformation with no coeval volcanic activity in the area of the deposit which prevented devolitalization of the oxidized parent magma in the large productive magma chamber inferred to have underlain el teniente at 4 km below the paleosurface this allowed igneous fractionation involving the recharge of mantle derived mafic magmas into the base of the chamber as well as volatile transfer and concentration near its roof to produce the cu and s rich magmas that formed the anhydrite bearing intrusive rocks

behavior of gold in the lateritic equatorial environment weathering and surface dispersion of residual gold particles at dondo mobi gabon abstract a supergene gold dispersion halo has developed at dondo mobi southern gabon from the weathering of an auriferous lisvenite under equatorial humid rain forest conditions morphological and chemical studies were performed on gold particles extracted from both fresh and weathered rocks from different parts of the dispersion halo the results demonstrate that the gold particles are residual and are subjected to increasing weathering upward through the profile from the protore to the surface in the central part of the halo and at the surface both laterally upslope and downslope weathering continues downward into the formerly barren saprolites which were derived from proterozoic schist and archean gneiss rim of the halo thus the au content progressively decreases as does the ag content of gold particles with distance from the center of the ore body gold particles subjected to increased weathering are smaller with more rounded shapes and surfaces pitted by dissolution the dispersion pattern is controlled by au dissolution and translocation of residual gold particles these processes involve an autochthonous evolution in the central part of the halo and a para autochthonous evolution at the rim of the halo at dondo mobi chloride and humic substances are the only ligands present in significant concentrations that are capable of complexing au thermodynamic calculations demonstrate that under such acidic conditions ph ranges from 4 to 6 gold stability increases with increasing silver content the dominant au complexes formed have been calculated to be an aurous hydroxichloride complex and an organometallic complex both of which are stable at surficial conditions thus both chemical and translocation processes control the mobility of au and gold particles in equatorial lateritic weathering profiles

petrological differentiation patterns and geomorphic distribution of ferricretes in central africa geomorphic distribution and petrological differentiation patterns of ferricretes widespread on landsurfaces were studied in the dembia zemio area southeastern central african republic four types of ferricretes are distributed on high plateaux hillslopes and low plateaux the main contrast corresponds to the differentiation between ferricretes of high plateaux rich in poorly hydrated minerals hematite and kaolinite and those covering hillslopes and low plateaux richer in hydrated minerals goethite and gibbsite a principal component analysis of geochemical and mineralogical data was used to characterize the main differentiation patterns of ferricretes in relation with their petrographic facies and the geomorphic features of the landscape the distribution of secondary minerals and their relationships to trace elements within and between the ferricrete types reflects differences in weathering and erosion processes our results document that the petrological patterns and the distribution of ferricretes are related to geomorphic features depending on hydroclimatic variations that govern the landscape evolution of many tropical shields

pan african tectonics in northwestern cameroon implication for the history of western gondwana abstract three main tectonic events related to pan african collision and post collision evolution have been identified in cameroon i crustal thickening ii left lateral wrench movements and iii right lateral wrench movements successively correlation of these events throughout the pan african belt and an integrated synthesis that includes the domains of central africa trans sahara and ne brazil enable us to define an indent type structure in northwestern cameroon this one suggests the existence of a rigid prong in this area which collided with the sao francisco congo craton sfcc active margin at ca 640 ma prior to subsequent widespread remobilization and granitization that partly affected both landmasses between 640 and 580 ma major indent related shear zones were further reactivated during regional clockwise rotation of the newly stabilized domain of northwestern cameroon suggesting that collision with the west african craton wac was still active after 580 ma geodynamic implications of this model are discussed in the context of the pan african global evolution in western gondwana

geological geochemical and mineralogical characteristics of the mandan and deh now bauxite deposits zagros fold belt iran the mandan and deh now bauxite deposits are located 40 km northeast of the dehdasht city in the zagros simply fold belt these deposits occur in eroded major nw se trending anticlines and occupy karst cavities near or at the boundary between the sarvak and ilam formations local uplifts at the end of the cenomanian and the mid turonian caused erosion and karstification of the sarvak formation these unconformities in the upper cretaceous favoured the formation and enrichment of bauxite deposits in the zagros fold belt the bauxite sequence in the mandan deposit consists of white gray black pisolitic red and yellow bauxites this sequence was repeated in the deh now area but without gray and black bauxites the present mineralogical studies of the sarvak formation and the mandan and deh now bauxite deposits indicate oxidizing to reducing conditions during the upper cretaceous in the zagros fold belt which had a significant effect on the compositions of the bauxites at least two phases of bauxitization can be distinguished in the study area i an oxidizing phase represented by boehmite diaspore hematite and kaolinite and ii a reducing phase represented by pyrite and chlorite geochemical data show that trace elements like zr hf nb ta th and u were enriched during bauxitization the bauxite deposits and carbonate rocks show similar ree patterns namely they are enriched in rees although the lrees are more enriched than the hrees mass change calculations demonstrate that mg mn ca k and p2o5 were leached out of the weathered system whereas al fe and si become concentrated in the residual system this study indicates that the mandan and deh now deposits are karst type bauxites formed by karstification and weathering of the sarvak formation

piecewise linear model for large strain radial consolidation a piecewise linear model for radial consolidation called rcs1 is presented rcs1 accounts for vertical strain soil self weight hydraulic conductivity anisotropy radial and vertical flows soil

chemical and mineralogical signatures of gold formed in oxidizing chloride hydrothermal systems and their significance within populations of placer gold grains collected during reconnaissance the close association of pd with au has been previously reported in highly oxidized chloride hydrothermal systems from several regions including australia brazil poland and the united kingdom the distinctive mineralization precipitated usually as a consequence of contact with reducing environments is characterized by au alloys containing low ag pd hg cu associated with selenides tellurides antimonides arsenides placer gold grains derived from this style of mineralization inherit these chemical and physical characteristics which are shown to be distinct from those placer grains derived from other styles of mineralization the discovery of placer gold grains of this type in areas remote from known in situ mineralization initiated the present project and provided a methodology for the study of a relatively large number of occurrences data describing alloy chemistry and mineralogy of polished sections of 957 placer grains from 19 localities in the united kingdom and 1 locality in the czech republic have augmented previously published data for 303 gold grains from 10 localities in the united kingdom six generic gold alloy types have been identified based on the relative proportions of au ag pd and hg mineralogical descriptions of similar gold alloys from localities worldwide usually conform to this classification but slight deviations are noted where p t conditions differ from those previously identified in devon alloy types may occur either as discrete grains or as phases within heterogeneous grains type 1 gold defined as 99 mass au type 2 gold au pd and type 3 gold au ag alloys with selenide inclusions are the most common compositions and occur at most localities although in different proportions type 4 gold is also an au ag alloy but contains sulfide and sulfarsenide inclusions gold alloys or intermetallics containing pd hg and or pd sb alloys type 5 and cu type 6 are found only at some localities as is a variety of type 3 gold selenide inclusions which contains hg the spatial arrangement of the main alloy types within heterogeneous gold grains shows a consistent precipitation order of type 1 type 2 and type 3 independent of locality interpretation of the chemical controls on alloy precipitation indicates that o2 controls whether type 1 or type 2 gold precipitates initially the formation of type 4 gold au ag alloys with sulfide inclusions is ascribed to a fall in o2 to around the hematite magnetite buffer where hs aq replaces cl aq as the aqueous gold complex types 3 and 5 gold commonly mantle earlier alloys and show evidence for aggressive replacement of the core this texture is interpreted as evidence for influx of a more oxidizing fluid which also accounts for the abundance of selenide and telluride mineral inclusions within this gold type this approach provides a plausible explanation of the complex heterogeneity within and between gold grains from the localities and accounts for the common sequence of alloy precipitation without invoking multiple episodes of hydrothermal activity to account for different alloys however the absence of thermodynamic data describing the au cu au ag cu and au ag pd hg systems prevents interpretation of the significance of some alloy types this study has demonstrated that gold mineralization associated with oxidizing strata is more widespread than currently appreciated the methodology described here not only permits identification of gold from this style of mineralization but allows initial evaluation of the economic potential of the source through the study of the alloy types this information may be gained at an early stage in the exploration process from gold grains collected during routine reconnaissance

numerical modeling of sand drain performance a case study of the salter street bridge construction several bridge crossings proposed for the red river floodway expansion project were recently constructed using vertical sand drains to accelerate excess pore water pressure dissipation and settleme

vertical drain consolidation with non darcian flow and void ratio dependent compressibility and permeability vertical drains increase the rate of consolidation in soft soils by facilitating faster dissipation of excess pore water pressure through short horizontal drainage paths this paper presents an analytical solution for non linear radial consolidation under equal strain conditions incorporating smear but ignoring well resistance three aspects of non linearity are considered a non darcian flow b a log linear void ratio stress relationship and b a log linear void ratio permeability relationship the analytical solution to non linear radial consolidation can explicitly capture the behaviour of both overconsolidated and normally consolidated soils for non linear material properties consolidation may be faster or slower when compared with the cases with constant material properties the difference depends on the compressibility permeability ratios cc ck and cr ck the preconsolidation pressure and the stress increase if cc ck 1 or cr ck 1 then the coefficient of consolidation increases as exc

physical modelling of consolidation of hong kong marine clay with prefabricated vertical drains in this study a small scale physical model with full instrumentation was set up and used to measure the full consolidation process of a cylinder of clay with one prefabricated vertical drain pvd in its middle the model test produced several interesting phenomena i a delayed pore water pressure increase under a constant pressure during loading stages ii a delayed pore water pressure decrease under a constant pressure during unloading stages and iii residual excess pore water pressures at the end of loading two analytical solutions accounting for the well resistance and a smear zone with reduced permeability are used to calculate the variation of average excess pore water pressure with time and these are compared with the measured variation the well resistance of the pvd has a larger influence on the consolidation process than the permeability of the smear zone especially during the latter stages of consolidation the analytical solutions are able to show the influence of the well resistanc

finite element analysis of an embankment on a soft estuarine deposit using an elastic viscoplastic soil model a new elastic viscoplastic evp soil model has been used to simulate the measured deformation response of a soft estuarine soil loaded by a stage constructed embankment the simulation incorporate

magmatic evolution of the giant el teniente cu mo deposit central chile elteniente the world s largest cu deposit is hosted in late miocene and pliocene plutons that intrude the older teniente volcanic complex or farellones fm 14 2 6 5 ma the late miocene and pliocene plutonic host rocks of the deposit include sequentially the relatively large 450 km teniente mafic complex laccolith 8 9 1 4 ma the smaller 30 km sewell equigranular tonalite complex 7 05 0 14 ma and associated andesitic sills 8 2 0 5 to 6 6 0 4 ma small dacitic porphyry stocks 51km 6 09 0 18 ma the unusual cuand s rich porphyry a anhydrite bearing granitoid stock 51km 5 67 0 19 ma the teniente dacite porphyry dike 51km 5 28 0 10 ma minor latite dikes 4 82 0 09 ma and finally a small dacite intrusion 4 58 0 10 ma these plutonic rocks are all isotopically similar to each other sr sr1 4 0 7039 0 7042 end1 4 2 5 to 3 5 and also to the teniente volcanic complex extrusive rocks but distinct from both older late oligocene to early miocene volcanic rocks sr sr1 4 0 7033 0 7039 end1 4 3 8 to 6 2 and younger pliocene post mineralization mafic dikes and lavas sr sr1 4 0 7041 0 7049 end1 4 1 1 to 1 1 multiple cu mineralized magmatic hydrothermal breccia pipes were emplaced into these plutonic rocks during the same time period as the felsic porphyry intrusions between at least 6 31 0 03 and 4 42 0 02 ma these mineralized breccia pipes which formed by exsolution of magmatic fluids from cooling plutons have their roots below the deepest level of mining and exploration drilling and were derived from the same magma chamber as the felsic porphyries 44 km below the paleosurface to produce the 100 10 tonnes of cu in the deposit requires a batholith size 4600 km amount of magma with 100 ppm cu we suggest that both the mineralized magmatic hydrothermal breccias and the progressively smaller volumes of more fractionated but isotopically equivalent late miocene and pliocene felsic plutonic rocks that host the deposit were derived from the roof of a large long lived thermally and chemically stratified open system magma chamber or magmatic plumbing system recharged from below by mantle derived magmas only when this system fully solidified did post mineralization mafic olivine hornblende lamprophyre dikes 3 85 0 18 to 2 9 0 6 ma pass through the system from the mantle to the surface the significant progressive temporal isotopic evolution to higher sr sr from 0 7033 to 0 7049 and lower end from 6 2 to 1 1 that occurred between the late oligocene and pliocene in the vicinity of el teniente for mafic mantle derived magmas and by implication their sub arc mantle source region was due in part to increased mantle source region contamination by subducted crust tectonically eroded off the continental margin the post mineralization olivine hornblende lamprophyres also imply extensive hydration of the mantle below this portion of the andean arc by the pliocene which may have played a role in producing oxidized volatile rich magmas and mineralization at elteniente

galena lead isotopic variations in a mesozoic cenozoic andean arc antarctic peninsula the antarctic peninsula magmatic arc was the site of andean type subduction from at least silurian times to the late cenozoic hydrothermal galenas from eight localities in accretionary complex arc volcanic sequences and plutonic rocks along a strike length of 1100 km have restricted 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb compositions 18 628 18 734 15 599 15 673 and 38 441 38 689 respectively plotting on crustal average growth curves the local geological setting and comparison with andean leads suggest that the major source reservoir was isotopically homogeneous sedimentary rocks forming the late palaeozoic triassic accretionary complex the lead data suggest that old continental basement is absent at least as far south as 65 s galenas from a large 13 2 km epithermal vein system on hurd peninsula fall in three populations a main isotopically homogenous array 18 643 15 647 and 38 503 2 0 020 0 020 and 0 050 n 33 interpreted as a large hydrothermal system that extracted homogenous leads from early triassic turbidites two smaller sub populations with more radiogenic 206 pb 204 pb are associated with mid to late cretaceous intrusive rocks and may represent either local contributions of magmatic lead or younger hydrothermal episodes in western graham land two localities associated with mantle derived mafic intrusions of cenozoic age have low 207 pb 204 pb and 208 pb 204 pb ratios indicating addition of some mantle type lead

plane strain lateral consolidation with non darcian flow new plane strain lateral consolidation equations are formulated that neglect the well resistance of vertical drains but are applicable for both darcian and non darcian flow the results of consolidation analyses using conventional darcian linear flow and the new solution based on non darcian exponential flow are compared a good match has been obtained between equivalent plane strain and axisymmetric solutions the advantage of the equivalent plane strain procedure is that it not only matches the average degree of radial axisymmetric consolidation but also yields a more realistic excess pore pressure distribution in the lateral direction than the darcian flow condition the relevant parameters are illustrated graphically for convenience good agreement was obtained between the prediction of the new equivalent plane strain solution and field data from a test area in ska edeby sweden key words plane strain consolidation soft clay vertical drains

consolidation of soil using vertical drains the use of vertical drains is examined critically in view of the fact that in half a century of use there have been a large number of occasions when vertical drains have failed to promote a more rapid consolidation of the soil under load the mode of operation of the drain is discussed and it is shown that an understanding of this has affected the design of the more recent band shaped drains the effects of smear and drain resistance are also discussed reference is made to a three dimensional finite difference computer program modelling the flow of excess pore water in the drain and the surrounding soil which is used to aid in the drain design specific cases which can also be analysed by published techniques have been used to check the validity of the model consideration is also given to the methods of site investigation which should be employed to obtain the appropriate soil parameters for design cases are cited where a lack of data on the soil parameters has restricted the design of the vertical dr

numerical assessment of equivalent diameter equations for prefabricated vertical drains the design approaches to prefabricated vertical drains pvds for different geotechnical and geoenvironmental engineering applications involve converting the pvd s rectangular band shape to an equivalent circular shape to simplify the analytical analysis several equivalent diameter equations for pvds are available in the literature however these equations produce different equivalent diameters and no definitive recommendation is available regarding their validity the aim of this study is to assess numerically the validity of these equations and identify the most appropriate one for use in design

implications of pb isotope signatures of rocks and iron oxide cu au ores in the candelaria punta del cobre district chile lead isotope ratios of ores of the candelaria punta del cobre iron oxide cu au deposits and associated early cretaceous volcanic and batholithic rocks have been determined for the igneous rocks a whole rock acid attack technique based on the separate analyses of a leachate and the residual fraction of a sample was used the lead isotope systematics of leachate residue pairs are significantly different for unaltered and altered igneous rocks of the candelaria punta del cobre district residues of unaltered igneous rocks likely represent the common lead in contrast residues of all the altered igneous rocks except two samples have higher pb isotope ratios than those of unaltered magmatic rocks and cannot represent common lead we suggest that this is a result of the hydrothermal alteration suffered by these rocks and that the common lead composition of the altered igneous volcanic and plutonic rocks must have been similar to that of the unaltered batholith rocks the conclusion that the altered volcanic rocks originally had a similar common lead isotope composition as the batholith is consistent with geological and geochemical arguments e g setting regional geologic evolution ages and relative distribution of volcanic and intrusive rocks magmatic affinities which indicate that these rocks were derived from similar early cretaceous parent magmas the modification of the leachate residue pair lead isotope systematics of most altered igneous rocks is consistent with a selective removal of lead and uranium from these rocks by an oxidized hydrothermal fluid the result of the hydrothermal leaching has been to alter magmatic rocks in a way that 1 their leachable fraction is presently a mix of common lead similar to that of the ore event and of radiogenic lead evolved from a source with a consistently high th u and that 2 their residual fraction has less common lead than unaltered rocks the outcrop area with altered volcanic rocks displaying anomalously high lead isotope ratios extends over 25 km along the eastern margin of the batholith since lead of the ores in the candelaria punta del cobre district has the same isotopic composition as the common lead of unaltered magmatic rocks of the area the lead isotope data are consistent with a derivation of the ore lead and by inference of other metals like cu both directly from a magmatic fluid exsolved during crystallization of the batholith and or from hydrothermal leaching of the volcanic rocks originally having similar isotopic compositions as the batholith

consolidation modelling of soils under the test embankment at chek lap kok international airport in hong kong using a simplified finite element method this paper models consolidation of the foundation soils under a test embankment at the new chek lap kok international airport in hong kong the modelling used a simplified finite element method and material parameters derived from results in the original site investigation report various features that need to be considered in applying the simplified method are illustrated through this case study good predictions of settlement results are obtained relatively large discrepancies in pore water pressure predictions suggest that the nonlinear nature of hydraulic conductivity needs to be taken into account when large compressions are likely to occur geological conditions are shown to be a key factor in successful modelling of consolidation behaviour key words consolidation pore water pressure case modelling finite element method vertical drains settlement

geologic and metallogenic significance of the isotopic composition of lead in galenas of the chilean andes eighty galena samples from different mineral deposits within the chilean andes from the mesozoic and cenozoic eras were analyzed for lead isotopes the results show a restricted dispersion between 18 65 to 18 28 15 68 to 15 56 and 38 72 to 38 11 on 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios respectively galenas from deposits hosted by pre jurassic to jurassic rocks are relatively enriched in radiogenic pb reflecting the involvement of old crustal pb galenas from lower cretaceous hosted deposits are less radiogenic and may reflect a mantlelike component those from tertiary rocks are isotopically more variable reflecting the influence of a more evolved crust there is no obvious correlation between the isotopic composition of the galena leads and the age of the hydrothermal event that gave rise to the particular mineral deposit when such ages can be determined from independent geologic evidence it is concluded that the galena leads were derived from a mixture of different lead reservoirs as defined in zartman and doe 1981 the correlation of isotopic composition with age of host rocks suggests either that the concentration of lead to form galena was more or less contemporaneous with the formation of the host rock or that the galena lead was essentially derived from the country rocks and inherited their original isotopic signature other workers have reported an overall similarity between the isotopic composition of galena leads and whole rock leads from the chilean andes however the isotopic compositions of galena leads from the argentinian andes show different characteristics from those of the chilean andes but the data are insufficient to allow firm conclusions

laboratory determination of smear zone due to vertical drain installation this paper is mainly concerned with a laboratory study to investigate the effect of smear due to vertical drain installation the extent of the smear zone around a vertical drain was studied utilizing a large scale consolidometer apparatus the test results reveal that a significant reduction in the horizontal permeability takes place toward the central drain whereas the vertical permeability remains relatively unchanged the radius of the smear zone was estimated to be a factor of four to five times the radius of the central drain mandrel and the measured ratio of horizontal to vertical permeability approached unity at the drain soil interface the laboratory measured settlements are subsequently compared with the predictions based on the theory of hansbo and the finite element method it is of relevance to note that the inclusion of the correct variation of permeability ratios of the smear zone in the plane strain finite element analysis improves the accuracy of settlement predictions

aspects of vertical drain design darcian or non darcian flow the classical consolidation equations developed by barron in 1944 and 1948 are well known among engineers working on soil improvement by preloading in combination with installation of vertical drains these equations have been gradually refined and are generally utilized in conventional design the design may seem simple in theory but is connected with a great number of uncertainties from a practical point of view the problems connected with the choice of consolidation parameters will be commented on and practical advice for the design will be given in this paper a number of case records will be presented and compared with on one hand the conventional method of design and on the other hand the so called method developed by the author in 1960 to take into account the effect of smear the method is based on an exponential correlation between hydraulic gradient and flow velocity we find that the correlation between the conventional theory and practice based on back analysis of field data is les

radial consolidation of clay using compressibility indices and varying horizontal permeability a system of vertical drains with surcharge load to accelerate consolidation by shortening the drainage path is one of the most popular methods of soft ground improvement the conventional radial consolidation theory including smear and well resistance has been commonly used to predict the behaviour of vertical drains in soft clay its mathematical formulation is based on the small strain theory and for a given stress range a constant volume compressibility mv and a constant coefficient of horizontal permeability kh are assumed however the value of mv varies along the consolidation curve over a wide range of applied pressure p in the same manner kh also changes with the void ratio e in this paper the writers have replaced mv with the compressibility indices cc and cr which define the slopes of the e log relationship moreover the variation of the horizontal permeability coefficient kh with the void ratio e during consolidation is represented by the e log kh relationship

mineralogical and isotopic zonation in the sur sur tourmaline breccia rio blanco los bronces cu mo deposit chile implications for ore genesis the sur sur tourmaline breccia is located in the southeast part of the rio blanco los bronces porphyry copper molybdenum deposit central chile the breccia hosts approximately one quarter of the total resource of 57 mt of fine copper at rio blanco the breccia is hosted within and contains altered clasts of granodiorite from the 12 to 8 ma san francisco batholith which intruded a sequence of miocene volcanic and volcaniclastic rocks a series of weakly mineralized to barren felsic porphyries cut the breccia and indicate a minimum age of approximately 6 ma for mineralization at sur sur the sur sur breccia dike is at least 3 km long 0 2 km wide and has a vertical extent of at least 1 km the breccia has been cemented by early biotite and anhydrite at depth and by tourmaline and specularite at higher altitudes these early formed cements have been overgrown and in some cases replaced by chalcopyrite magnetite pyrite and quartz mineralogical zonation in the breccia includes a transition from biotite cement and related biotite alteration upward to tourmaline cement and quartz sericite tourmaline alteration at approximately 3 000 m elevation iron oxide minerals are also zoned with a transition upward from a magnetite dominated zone below 3 330 m to a specularite dominated zone above 3 600 m pyrite is the dominant sulfide at altitudes above 4 000 m secondary liquid rich vapor rich and hypersaline fluid inclusions are preserved in quartz and tourmaline cement measured homogenization temperatures are mostly between 300 degrees and 450 degrees c and salinities range from 0 to 69 wt percent nacl equiv sulfur isotope compositions of sulfide cement range from 4 1 to 2 7 per mil the lowest delta 34s sulfide values are in samples from between 3 700 and 4 000 m elevation where they correspond to the highest copper grades in the tourmaline breccia this high grade zone also contains abundant specularite locally replaced by magnetite modeling of sulfate sulfide equilibrium indicate that approximately 150 degrees c of cooling over a vertical interval of 100 m would be required to account for the zonation of sulfide isotope compositions at sur sur making conductive cooling an unlikely ore forming mechanism measured 206pb 204pb values of lead in anhydrite cement in the sur sur tourmaline breccia and the rio blanco magmatic breccia range from 17 558 to 18 479 207pb 204pb values range from 15 534 to 15 623 and 208pb 204pb values range from 37 341 to 38 412 the lead in anhydrite is considerably less radiogenic than that indicated by values obtained previously for lead in sulfide ores and igneous host rocks at rio blanco los bronces the source of lead in anhydrite must have been from rocks external to the main magmatichydrothermal system probably the precordilleran basement a magmatic hydrothermal explosion from a deep seated crystallizing intrusion triggered breccia formation at sur sur hydrostatic pressures catastrophically exceeded lithostatic load plus the tensile strength of the confining granodiorite leading to widespread brecciation and subsequent invasion by large volumes of magmatic gas and hypersaline brine the low density gas phase carrying h2o so2 hcl and b2o3 separated physically from the dense copper bearing brine and flushed through the breccia column first where it condensed into ground waters of uncertain derivation anhydrite specularite and tourmaline were deposited from this lowsalinity acidic oxidized hybrid solution subsequent upwelling of magmatic hydrothermal brine resulted in sulfide deposition high grade copper deposition is interpreted to have occurred in response to mixing of the oxidized acidic water with the copper bearing magmatic hydrothermal brine

radial consolidation with vertical drains and general time dependent loading a simple to use analytical solution for radial consolidation with vertical drains under equal strain conditions is presented in this paper this solution accounts for the effects of soil smear dra

mineralogy geochemistry and age constraints on the zn pb skarn deposit of maria cristina quebrada galena northern chile the maria cristina zn pb skarn deposit hosted by carbonate rocks of the lower cretaceous chanarcillo group in northern chile is described to provide a basis of comparison to adjacent 2 km barite deposits and regional pb zn and ba deposits with mississippi valley type affinities strongly retrograded garnet andradite to ad30gr70 diopsidic pyroxene and epidote skarn and barite bearing massive sulfides sphalerite pyrite galena marcasite magnetite occur at the contact of potassically altered diorite porphyry of mid cretaceous age the skarn mineral compositions similar to those of cu skarns may reflect emplacement in a high f o2 context sulfur isotope values of sulfides 8 8 to 7 1 and barite 14 0 26 1 indicate disequilibrium conditions and different sulfur sources including magmatic sulfur lead isotope ratios of galena and strontium isotope ratios of barite indicate a similar metal reservoir for the different ore deposit types constituted by the intercalated lower cretaceous volcanic rocks or mid cretaceous intrusive rocks 40ar 39ar dating of hydrothermal k feldspar suggests an age between 94 and 90 ma for the mineralization

sources of lead in the san cristobal pulacayo and potosi mining districts bolivia and a reevaluation of regional ore lead isotope provinces new lead isotope data on ores crustal rocks and leachates of crustal rocks combined with data in the literature provide important new constraints on the sources of ore metals in southwest to south central bolivia including the very large recently discovered silver zinc deposit at san cristobal the pulacayo polymetallic district and the giant potosi silver tin base metal deposit lead isotope ratios of ores and igneous rocks from the san cristobal deposit and from paleozoic and cretaceous sedimentary rocks are compared with published data on high grade middle proterozoic metamorphic basement rocks these data constrain the major source of lead and by inference of other ore metals at san cristobal to be the metamorphic basement rocks leaching experiments on samples of paleozoic and cretaceous sedimentary rocks show that the easily leachable lead from these rocks is much less radiogenic than the whole rock compositions however lead isotope ratios of both whole rocks and leachates of these upper crustal rocks are too radiogenic for them to be major sources of ore lead at san cristobal lead isotope ratios of ores from pulacayo and potosi are similar to each other and lie within the range of paleozoic and cretaceous sedimentary whole rock compositions leaching of pb from the sedimentary rocks cannot explain the isotopic compositions of the pulacayo and potosi ores and the isotopic homogeneity of the potosi ores also argues against mixing of lead from diverse sources in the hydrothermal system lead from the sedimentary rocks may have been incorporated by magmatic assimilation followed by extraction of ore metals from the resulting magma lead isotope ratios of san cristobal ores are different from those of pulacayo potosi and other deposits to the east but resemble the compositions of ores and volcanic rocks in western bolivia on this basis we identify a new ore lead isotope province extending from san cristobal northward across the eastern altiplano and into southern peru this province is coincident with but smaller than the extent of the proposed arequipa antofalla metamorphic basement craton the degree of incorporation of ore metals from the metamorphic basement appears to depend on the timing and or location of the mineralizing event ore deposits in the northern part of province iv formed before the thickening of andean crust beginning around 20 ma and incorporated minor amounts of metals from the metamorphic basement younger deposits farther to the south contain major to dominant components of basement lead

consolidation analysis of a stratified soil with vertical and horizontal drainage using the spectral method a novel use of the spectral method to determine excess pore water pressure during vertical consolidation of multi layered soil with time constant material properties is presented considering a unit cell with combined vertical and radial drainage equal strain conditions are assumed in the analysis the novel adoption of material properties that vary in a linear fashion with depth allows arbitrary distributions of properties to be modelled by incorporating surcharge and vacuum loading that vary with both depth and time a wide range of consolidation problems can be analysed the spectral method is a meshless approach producing a series solution to the consolidation problem based on matrix operations accuracy can be improved by increasing the number of terms used in the series solution the model is verified by the analysis of selected case studies characterised by analytical free strain consolidation with thin sand layers surcharge only laboratory test and embankment trial with surcharge and vacuum

relationship between copper tonnage of chilean base metal porphyry deposits and os isotope ratios re os isotopes in pyrite and chalcopyrite from early high temperature hypogene alteration assemblages in chilean porphyry copper deposits identify the source of os and by inference cu in these ore systems typical concentrations for os in both pyrite and chalcopyrite are between 7 and 30 ppt 10 12 g g and for re between 0 200 and 10 ppb 10 9 g g re os isochrons yield ages and initial 187 os 188 os ratios for the sulfides the isotopic data reflect the relative contributions of copper from the mantle and crust in chilean porphyry copper deposits seven ore deposits that reside in different tectonic terranes and represent distinct epochs of mineralization in chile were studied the initial osmium ratios of the first stage of mineralization at each of the deposits range from 0 15 to 5 these values are more radiogenic than the present chondritic mantle 0 13 and indicate significant crustal contributions of os to the magmatic and or hydrothermal systems there is a strong correspondence between the total copper content and initial os isotopic ratios in base metal porphyry deposits the larger deposits have lower initial os ratios than the smaller less significant deposits this relationship implies that larger deposits acquire a greater proportion of os from the mantle the initial os ratio of samples in the central segment of porphyry copper deposits of northern chile also decreases with decreasing age of the deposit a plausible interpretation of the re os data is that the later and larger deposits use regional tectonic and structural features that allow sampling of deeper more primitive magmatic sources

evaluation of simulation models of lateral spread sites treated with prefabricated vertical drains abstractfinite element analyses are performed of centrifuge tests consisting of untreated and drain treated lateral spread sites with the goal of evaluating the ability of numerical simulations to predict the response of sites improved with prefabricated vertical drains finite element models of varying complexity are analyzed a two dimensional model of the full centrifuge test a three dimensional unit cell model around a single drain and a two dimensional unit cell model all the finite element models predict pore pressures consistent with the centrifuge tests the deformation responses of the finite element models show that unit cell analyses produce significantly larger deformations than those observed in the centrifuge this result is caused by the fact that the centrifuge test geometry is not well represented by the infinite slope condition assumed in a unit cell the full two dimensional model predicts deformations that are more consistent with those of the centrifuge because it can capture the

factors controlling the trace element distribution in fine grained rocks the albian kaolinite rich deposits of the oliete basin ne spain abstract this paper combines mineralogical data x ray diffraction petrographic and scanning electron microscopy techniques and geochemical analyses in order to investigate the composition of a set of samples claystones siltstones and sandstones which belong to the albian deposits of the oliete basin in spain the aims of the study are to characterize the distribution of major and trace elements in kaolinite rich rocks to infer the role played by accessory phases and clay minerals on the trace element distribution and to assess the source area composition of these materials mineralogical analyses show that these rocks are mainly composed of different proportions of quartz and clay minerals kaolinite and illite with minor feldspar micron accessory minerals such as monazite zircon pyrite marcasite fe oxides and ti oxides have also been detected the sandstone framework implies that the source area of these sediments was probably a granitoid source which underwent low rank metamorphism the major element distribution reflects the mineralogy of the rocks plots in the a cn k diagram as well as their cia values indicate that these sediments were generated from an intensely weathered source area this produced the development of relatively cation poor clays such as kaolinite and claystones with large rare earth elements ree contents the fact that transition element contents in claystones are greater than in siltstones and sandstones suggests that they are preferentially linked to clay minerals probably by surficial sorption in comparison with other lithologies the high abundances of high field strength elements in siltstones imply that accessory minerals such as zircon and nb bearing phases are mainly concentrated in siltstones it should be noted that siltstones are also the lithology which displays the highest ree abundances the statistical analysis of the geochemical data suggests that ree are mainly controlled by ti and nb bearing phases such as titanite and nb and ti oxides although clay minerals are not the main phases in the ree control they probably also have some influence as the analyses show in addition other accessory phases such as monazite secondary phosphates and zircon also contribute to the ree contents although much less than amorphous fe oxides in some samples according to the ree patterns and elemental ratios such as la sc th sc th co etc the source area of the studied outcrops was probably felsic and with intermediate composition between granite and granodiorite

the efficiency of partially penetrating vertical drains the paper deals with the problem of consolidation of a clay layer in which vertical partially penetrating drains have been installed the influence of well resistance is considered in the analysis which is performed by means of the finite element method the drainage pattern for each drain is assumed to be axisymmetric diagrams of the average degree of consolidation versus time for some selected non dimensional parameters are presented these dia grams indicate for partially penetrating drains that the delay in the consolidation process within the zone penetrated by drains due to higher excess porewater pressure in the underlying undrained zone is noticeable only to a very limited height above the drain tips in the case studies presented the delay is negligible to a depth corresponding to at least 80 of the partially penetrating drain length l article concerne le probleme de la consolidation d une couche d argile dans laquelle on a installe des drains verticaux qui penetrent partiellement l inf

modelling consolidation accelerated by vertical drains in soils subject to creep the settlement of embankments and reclamations over soft soils is frequently accelerated by the use of vertical drains the magnitude of long term settlement is sometimes reduced by the use of surcharge although there is often uncertainty about how long the surcharge should be maintained to minimise creep movement the design of vertical drains is generally based on closed form solutions of terzaghi s consolidation equation and rarely takes into account non linear stiffness and creep of the soil in this paper a one dimensional finite difference consolidation analysis is outlined showing how vertical and radial drainage of a multi layer soil profile in the zone of influence of a vertical drain may be modelled the analysis allows inclusion of a zone of peripheral smear around the drain and drain resistance permeabilities may be varied with void ratio and creep is modelled both during and after primary consolidation the application of the model is illustrated with back analysis of field data from cons

weathering and soil forming processes under semi arid conditions in two mexican volcanic ash soils abstract weathering and neoformation of allophane imogolite and halloysite in volcanic ash soils have been studied extensively in humid climates but little data are available on these soils in arid and semi arid conditions weathering and soil formation under semi arid conditions on acid pyroclastics have been investigated in two profiles both at the micro site scale and on bulk samples xr microdiffractions and sem edx microanalysis were performed on soil thin sections chemical particle size xrd and mineral identification analysis were performed on conventional soil samples results show the interplay of various sub processes a intense division of the coarse minerals into small fragments 50 200 m in size b diagenesis of noncrystalline products in the zone of contact with the parent minerals c transformation of noncrystalline minerals into halloysite in the compact soil microstructures and preservation of the noncrystalline minerals in the topsoil d desiccation and condensation of the crystalline and noncrystalline minerals into microaggregates in the topsoil the results of these interacting weathering processes are silty loam soils with no cohesion and high susceptibility to wind erosion differences appearing between different analytical methods at different sampling scales need special precautions in explaining the results

plane strain modeling of smear effects associated with vertical drains the present study provides a methodology to include the smear effect of vertical drains in a two dimensional 2d plane strain finite element model employing the modified cam clay theory the analysis is conducted by converting the radius of the smear zone and its permeability axisymmetric into equivalent plane strain parameters the introduction of smear effects improves the accuracy of the numerical model that is tested for a malaysian soft clay in this study

distribution of duricrusted bauxites and laterites on the bamileke plateau west cameroon constraints from gis mapping and geochemistry estimation of the mineral resources potential is an important issue for most of developing countries the spatial distribution of bauxites and lateritic land surfaces on the bamileke plateau west cameroon has been investigated with a boolean modeling process into a gis environment on the basis of geological constraints such as elevation rock and soil types and landscape morphology field observation and srtm shuttle radar topographic mission data allowed the differentiation of two lateritic land surfaces separated by a minimum altitude difference of about 60 m these surfaces constrained by favorable rock types slope steepness and soil types provided a potential lateritic bauxitic area of 381 km 2 17 2 of the total study site field validation and the integration of legacy spatial data resulted in an area of 60 1 km 2 for potential bauxitic ores i e obviously duricrusted bauxitic surfaces with 47 8 km 2 in the upper surface and 12 3 km 2 in the lower surface alumina contents obtained from duricrust samples were analyzed by geostatistical methods and classical kriging interpolation to discriminate between bauxitic and ferruginous laterites this highlighted a geochemical trend from higher alumina values on the upper surface 40 66 wt to lower values on the lower surface 13 44 wt finally our study documents two duricrusted lateritic surfaces arranged in a staircase manner and having different geochemical characteristics the total bauxitic rich surface is distributed in five spots throughout the study area and covers 56 2 km 2 while ferruginous laterites occupy a spot of 3 9 km 2 gis mapping approach of lateritic land surfaces accounting for reliable constraints might be promising for larger scale investigations of mineral resources in cameroon

numerical modeling of vertical drains with smear and well resistance installed in soft clay this study describes the behavior of embankments stabilized with prefabricated vertical drains installed in soft clay foundations based on several fully instrumented case histories selected from thailand and malaysia a multidrain analysis is conducted based on an equivalent plane strain model developed by the authors the deformation of soft clay beneath an embankment i e along and away from the centerline is predicted and compared with the available field measurements the effects of both smear and well resistance are incorporated in the analytical formulation which is used in conjunction with the modified cam clay theory it is demonstrated that the installation of vertical drains significantly increases the rate of settlement improves the dissipation of pore water pressure and decreases the lateral deformation of the soft clay foundation to obtain better predictions especially of pore pressures and lateral displacements the equivalent discharge capacity of the drains needs to be modeled ap

copper gold and silver enrichment in ore mylonites within massive sulphide orebodies at hongtoushan vhms deposit n e china abstract the hongtoushan archaean cu zn volcanic hosted massive sulphide vhms deposit occurs in the hunbei granite greenstone terrane liaoning province of ne china the ores were metamorphosed 3 0 2 8 ga to upper amphibolite facies at temperatures between 600 and 650 c and underwent three phases of deformation the deformation has transposed the stratiform orebodies into a y shaped configuration ore minerals in the deposit were originally composed of pyrite pyrrhotite chalcopyrite and sphalerite prograde metamorphism obliterated almost all the sedimentary textures in the ores and the present ore textures were formed substantially during peak and post peak metamorphism intensive remobilisations have occurred in the hongtoushan deposit at various scales there are more than 30 oreshoots inside the main massive sulphide orebodies the oreshoots range from 2 to 30 m in length 0 1 to 1 5 m in width and 2 to 30 m in depth extension most run parallel or sub parallel to the strike of the massive sulphide ore layers with only a few being developed in metamorphic rocks in the immediate vicinity of the sulphide orebodies almost all the sulphide and gangue minerals in the oreshoots have been affected by intense shearing pyrite is characterised by cataclastic flow pyrrhotite chalcopyrite and sphalerite exhibit strong plasticity hydrothermal alteration minerals in the oreshoots are dominated by deformation free hornblende actinolite epidote clinozoisite biotite muscovite albite carbonate and quartz cu au and ag in the ore mylonites average 11 wt 1 74 and 235 g t respectively compared to the massive sulphide ores these oreshoots show remarkable enrichment of these elements with enrichment coefficients of 5 3 5 0 and 4 6 respectively we draw the conclusion that these oreshoots are actually ore mylonites overprinted by late stage fluids the presence of annealing textures in pyrrhotite and the absence in pyrite suggest that formation and succeeding annealing of the ore mylonite took place over the temperature range from 550 to 450 c such a temperature range combined with the geology and mineralogy indicates that these ore mylonites and the derivative oreshoots were formed during upper greenschist facies retrograde metamorphism similarity of the ore mylonites to the massive ores in metal varieties and lead isotope ages suggest that cu au and ag of the overprinting fluids on the ore mylonites were derived mainly from the nearby massive sulphide ores however lead isotope compositions of the ore mylonites also suggest that an external source such as the metamorphic host rocks has also contributed to their metal budget

pan african strike slip tectonics in eastern cameroon magnetic fabrics ams and structure in the lom basin and its gneissic basement abstract field microstructural and anisotropy of magnetic susceptibility ams or magnetic fabric studies were applied to identify the sequence and character of the pan african structures in the basement of eastern cameroon at both sides of the regional scale betare oya shear zone bosz the ne sw trending bosz separates older gneisses and migmatites towards se domain i from the younger rocks of the lom meta volcano sedimentary basin towards nw domain ii in domain i early ductile compressional deformation occurred in two events d1 and d2 under relatively high t conditions during subsequent cooling strain partitioned between the competent basement gneisses with only mild compression and the bordering shear zone bosz with intense simple shear wrenching d3 strain in the less competent rocks of domain ii is dominated by simple shear strike slip wrenching d3 with an earlier stage of compressional deformation preserved only in some low strain pods magnetic fabrics ams document a progressive change from oblate ellipsoids towards prolate ellipsoids in domain i when proceeding from the south towards the bosz foliations are mostly steep but define a girdle with a pole plunging gently towards wsw the magnetic lineations also plunge mostly towards wsw at shallow angles these fabrics indicate a compression approximately normal to the bosz which is also the se margin of the lom basin in the lom metasediments domain ii ams ellipsoids are typically oblate foliations trend ne sw with mostly steep dips magnetic lineations plunge gently ne or sw this fabric with foliations mostly steep and subparallel with the major bosz combined with generally subhorizontal lineations implies the bosz as a pan african strike slip shear zone with a subordinate component of compression at a larger scale the area is part of a continent scale shear zone separating external pan african domains of compression along the northern margin of the congo craton from internal domains dominated by high angle strike slip and transpressional deformation together with published data the present study thus demonstrates that transpression is a regional phenomenon in the pan african orogen of central and eastern cameroon

weathering mantles and their significance for geomorphological evolution of central and northern europe since the mesozoic abstract weathering mantles saprolites are very widespread in central western and northern europe where they form thick near surface residual deposits often in excess of 50 m they vary in the type of weathering the bedrock lithology involved the topographic setting and the age and stratigraphic context this review paper provides information about the distribution and major characteristics of weathering mantles from a number of key areas including the british isles the central european belt of mid mountains and uplands the scandinavian mountains and the fennoscandian shield it also examines the evidence for weathering etched origin of various landforms including boulders tors inselbergs basins and some regional landforms assemblages major types of regionally important weathering mantles include ferrallitic lateritic saprolites kaolinite rich saprolites sandy to grus mantles and various residuals left after partial dissolution of carbonate rocks although dating of weathering mantles is often circumstantial it appears sufficiently precise to argue for various ages of deep weathering mesozoic pre late cretaceous mantles are particularly widespread but there are also early tertiary and miocene saprolites widely present whilst most grus weathering is likely to be of miocene to pleistocene age individual upland areas have been subjected to multiple episodes of weathering whose legacy is the present day co existence of different weathering products continental and shallow marine deposits around the uplands particularly in the north sea and intra continental graben structures are often dominated by quartz and kaolinite pointing to deeply weathered land surfaces as the source areas and extending the record of weathering on the geological time scale they demonstrate that weathering mantles repeatedly formed and were subjected to erosion and new cycles of weathering were initiated we suggest that deep unroofing of basement structures in many parts of europe has been mainly accomplished by deep weathering and stripping of pre weathered rock the phenomenon of deep weathering has been very important for geomorphology etched landforms vary in size from small residual boulders up to regional characteristic landscapes etchsurfaces such as joint valley landscapes of southern sweden or undulating multi convex and multi concave landscapes of many uplands in central europe deep weathering has played a major part in the geomorphological evolution of europe since at least the late triassic and the concept involving long term etching and stripping provides an appropriate framework to describe and explain both erosional landscapes and sediment features

finite element modelling of vertical drains beneath embankments on soft ground a methodology is described for modelling vertical drains in plane strain finite element analyses of embankments on soft ground this includes the use of a suitably formulated drainage element to represent each drain criteria for matching the effect of a single drain in axisymmetric and plane strain analyses are developed on the basis of a widely accepted theory matching can be achieved by adjusting the geometry drain spacing and or the permeability of the soil the finite element analysis and matching procedure are validated by comparison with theoretical results the effects of both finite drain permeability well resistance and smear are modelled satisfactorily une methode est deacute acute crite pour simuler des drains verticaux dans une analyse aux elements finis a deformations planes de remblais sur sols mous ceci inclut l utilisation d un element de drainage formule de facon adequate pour representer chaque drain des criteres pour representer l effet d un drain unique dans les analyses axisy

the permeability of natural soft clays part ii permeability characteristics reply the permeability characteristics of a number of intact natural soft clays from quebec the usa and sweden have been investigated in the laboratory the variation of permeability with void ratio is best represented in terms of a linear e vs lg k relation which is generally valid in the range of volumetric strains encountered in engineering practice the permeability at the in situ void ratio is shown to be a complex function of such parameters as the void ratio the clay fraction the plasticity index and the fabric of the clay permeability anisotropy is negligible in marine clays the e vs lg k relationships of the various clays tested are well ordered in terms of an empirical parameter ip clay fraction irrespective of the geological origin of the clay the slope of the e vs lg k relationship referred to as permeability change index ck is simply related to the initial void ratio by ck 0 5eo keywords permeability clays laboratory tests permeability anisotropy permeability void ratio re

large strain vacuum assisted consolidation with non darcian radial flow incorporating varying permeability and compressibility abstracta numerical solution has been developed for large strain consolidation incorporating non darcian nonlinear radial flow with varying compressibility and permeability coefficients the solution can accommodate both conventional fill surcharge as well as vacuum preloading the smear effect caused by mandrel driven vertical drains is also captured in the analysis the proposed model is verified by comparing it with fem simulation existing laboratory data other existing theoretical solutions and its advantage of capturing the multiple factors influencing radial drainage and consolidation is demonstrated the effects of non darcian flow are found to be significant for obtaining an accurate solution unlike numerous past solutions that are based on linear darcy flow the salient finding of this study is that the conventional small strain theory can overestimate the rate of consolidation with radial drainage especially for highly compressible soils such as estuarine clays under substantial preloadin

pb isotopic compositions of some zn pb deposits and occurrences from urumieh dokhtar and sanandaj sirjan zones in iran abstract this study reports pb isotope ratios of galena pbs sampled from some zn pb deposits and occurrences n 18 within two major structural provinces of iran the sanandaj sirjan zone ssz and urumieh dokhtar zone udz regardless of the nature of the host rock and ore type the pb isotopic data plot in distinct isotopic fields according to their geographic situation which suggest that the structural terranes had an important control on the lead isotope compositions the zn pb deposits in the udz record distinctly higher 206pb 204pb and 208pb 204pb ratios compared to those within the ssz both zones however have radiogenic 207pb 204pb ratios 15 55 suggesting a dominant input of pb from crustal sources in thorogenic 208pb 204pb vs 206pb 204pb and uranogenic 207pb 204pb vs 206pb 204pb plots the pb isotope data define two linear arrays which may be attributed to mixing between mantle like end members and at least two distinct crustal sources characterized by high u pb and th u ratios in plumbotectonic discrimination diagrams the samples plot proximal to the orogenic curve which again supports interaction between crustal and mantle reservoirs however both neo tethys subduction and in particular mesozoic and tertiary orogenic activities seem to have played important roles in remobilizing pb and forming zn pb deposits in ssz and udz respectively the similarity of pb isotopic compositions between udz deposits and those for previously reported eocene volcanics demonstrates that long lived and widespread hydrothermal activity promoted remobilization of lead from the crust the latter occurred subsequent to neo tethys lithosphere subduction in the tertiary and continued subsequent the collision of the iranian and arabian plates in the miocene

equal strain consolidation by vertical drains this paper shows the development of a series of closed form solutions of equal strain consolidation in the presence of a vertical drain with smear and well resistance using an approach that considers the effects of both the radial and vertical drainage in a fully coupled fashion solutions are obtained for the excess pore pressure and the degree of consolidation in the compressible soil subjected to a step or ramp loading situation the closed form solutions in the present paper may be evaluated in an electronic spreadsheet on a standard personal computer

morphological mineral and geochemical characterization of soil profiles in meiganga as tools for rock weathering intensity and trend evaluation and residual ore deposit prospection in the mineralized domain of central cameroon

design procedure for vertical drains considering a linear variation of lateral permeability within the smear zone a system of vertical drains with surcharge preloading is an effective method for promoting radial drainage and accelerated soil consolidation this study presents a procedure for the design of vert

metal sources in mineral deposits and crustal rocks of ecuador 1 n 4 s a lead isotope synthesis ecuador consists of terranes having both continental chaucha tahuin loja terranes and oceanic macuchi alao salado terranes affinity which were accreted to the amazon craton from late jurassic to eocene four main magmatic arcs were formed by the subduction of the farallon nazca plate since the juras sic a jurassic continental arc on the western margin of the amazon craton a jurassic island arc alao terrane an early tertiary island arc macuchi terrane and a middle late tertiary continental arc encompassing the ter ranes of macuchi chaucha tahuin loja and alao after complete assembly of the ecuadorian crust mineral deposits formed during these magmatic arc activities include porphyry cu and gold skarn deposits in associa tion with the jurassic continental arc polymetallic volcanic hosted massive sulfide deposits vhms in associ ation with the jurassic island arc of alao au cu zn vhms deposits in association with the early tertiary is land arc of macuchi and porphyry cu and precious metal epithermal deposits in association with the middle late tertiary continental arc magmatism on the newly assembled crust of ecuador macuchi chaucha tahuin loja and alao terranes in this study we have compiled 148 new and 125 previously published lead isotope analyses on paleozoic to miocene metamorphic intrusive volcanic and volcanosedimentary rocks as well as on jurassic to miocene magmatic related ore deposits of ecuador lead isotope compositions of the magmatic rocks of the four main arc events derive from mixing of various sources including mantle variably enriched by pelagic sediments and or by a high 238u 204pb component and heterogeneous continental crust rocks lead isotope compositions of the ecuadorian ore deposits display a broad range of values 206pb 204pb 18 3 19 3 207pb 204pb 15 54 15 74 208pb 204pb 38 2 39 2 which is as large as the range previously re ported for all magmatic related ore deposits of the central andean provinces i and ii combined ore deposits formed before complete assembly of the ecuadorian crust through complete accretion of the several terranes i e pre eocene have lead isotope compositions overlapping those of the associated magmatic rocks sug gesting a largely magmatic origin for their lead in contrast post assembly ore deposits i e post eocene have lead isotope compositions that only partly overlap those of the coeval magmatic rocks of the continental arc in fact several ore deposits have lead isotope compositions shifted toward those of the basement rocks that host them suggesting that lead derives from a mixture of magmatic lead and basement rock lead leached by hy drothermal fluids most ecuadorian ores have high 207pb 204pb values 15 55 suggesting a dominant continental crust or pelagic sediment origin of the lead however we caution against concluding that chalcophile metals for ex ample cu and au also have a continental crust origin ore deposits of the different terranes of ecuador irrespective of their age plot in distinct isotopic fields which are internally homogeneous this suggests that lithologic factors had an important control on the lead isotope compositions ultimately lead isotope compositions of the ore deposits of ecuador mirror the isotopic compositions of the rocks of the host terranes and are consistent with the multiterrane nature of the ecuado rian crust

consolidation by vertical drains a theory is described which can be used in designing a vertical drainage system this theory incorporates important parameters such as vertical discharge capacity remoulding effects during installation and filter resistance the importance of these parameters is widely recognized but very seldom taken into account in the design by engineers six well documented case records related to different drain types are briefly presented experience gained from these case records shows that in many cases even if the overall performance appears successful there are aspects of soil drain behaviour that cannot be explained on the basis of existing theories l article decrit une theorie que l on peut appliquer a la conception d un systeme de drainage vertical cette theorie renferme d importants parametres tels que la capacite de decharge verticale les effets du remaniement pendant l installation et la resistance de filtration l importance de ces parametres est reconnue par bien des ingenieurs mais ils en tien

jurassic extensional tectono magmatism and associated mineralization of the el faldeo polymetallic district chilean patagonia geochemical and isotopic evidence of crustal contribution the el faldeo is the southernmost andean mineral district and consists of paleozoic polymetamorphic basement unconformably overlain by a 200 m thick homoclinal sequence of sedimentary and felsic volcanic beds of the ibanez formation in addition two epizonal intrusive units and related subvolcanic porphyries sills and dikes which intrude both the metamorphic basement and the ibanez formation are recognized the quebrada colorada granodiorite qcg and the cerro esmeralda tonalite cet the polymetallic mineralization was formed in four stages and includes pyrite arsenopyrite gold silver sphalerite galena and chalcopyrite hosted in felsic tuffs of the ibanez formation hydrothermal breccias and epizonal intrusions field observations and geochronological data u pb ar ar and fission track on cet rocks suggest 1 the development of subsiding pull apart basins and coeval formation of spaces for magmatic emplacement and mineralization in an extensional tectonic regime in mid jurassic time 2 a tectonic exhumation of the rocks of the district probably triggered by the chile ridge trench interactions that started in late miocene time sr nd isotopic data from cet samples and the pb isotope characteristics of galenas from the second and third mineralization stages are indicative of crustal contribution to the origin of the magmas and galena mineralization rocks of the paleozoic metamorphic basement are prime candidates for the crustal source components of the analyzed galenas

analysis of pv drains for mitigation of seismically induced ground deformations in sand slopes abstractprefabricated vertical pv drain arrays have been proposed as a minimally intrusive technique for mitigating seismically induced ground deformations in sandy liquefiable slopes this paper

stress state permeability relations for overconsolidated clays analysis of experimental data of soils in both the normally consolidated and overconsolidated states reveal that the proposed relationships are tenable preconsolidation stress level influences the level of permeability

an analytical solution for consolidation with vertical drains under multi ramp loading various analytical solutions have been proposed for a unit cell consolidation with a vertical drain under surcharge loading these solutions involve different assumptions to address various aspects of consolidation there is a lack of generalised solution for analysing consolidation of soil assisted by a vertical drain under various loading conditions this paper presents a simplified solution for consolidation under multi ramp loading generalised governing equations of equal strain consolidation are solved simultaneous radial and vertical flow conditions as well as the combined effects of drain resistance and smear are taken into account fully an increase in total stress due to multi ramp loading is reasonably modelled as a function of both time and depth an analytical solution to calculate excess pore water pressure at any arbitrary point in soil is derived by using the method of separation of variables the conventional definition of the degree of consolidation is given in terms of the dissipatio