dynamic soil pile foundation structure interaction records and predictions the problem of soil pile foundation superstructure interaction is examined and a simple rational procedure to analyse the response of a structure supported on pile groups is presented this proced

re os age of the pueblo viejo epithermal deposit dominican republic re os analyses of pyrite from the pueblo viejo high sulfidation epithermal deposit both monte negro and moore ore zones yield an isochron age of 111 9 3 7 ma and initial 187 os 188 os ratio of 0 22 0 18 mean square of weighted deviates 84 n 21 isochrons grouped by pyrite setting layered versus vein or locations yield ages within uncertainty of the overall isochron and with each other and as such do not yield temporally distinguishable ages sphalerite vein samples as well as shale source rocks show evidence of open system behavior and loss of re and therefore are not included in the above regression these results confirm that the pueblo viejo deposit is early cretaceous in age and coeval with the volcanic los ranchos formation which hosts the deposit recent paleontological age assignments for the hatillo formation which overlies the los ranchos formation show that it is only slightly younger opening the possibility that mineralization in the hatillo formation could also be related to late stages of los ranchos magmatism whether these revised los ranchos hatillo relations provide sufficient cover to account for the paragenetically late formation of pyrophyllite at pueblo viejo remains unclear recognition that pueblo viejo is coeval with the los ranchos formation shows that large scale high sulfidation epithermal mineralization can form from basal island arc tholeiitic magmatism a review of available experimental data confirms that these magmas can generate hydrothermal solutions of the necessary composition favorability of the los ranchos formation might have been enhanced by its bimodal composition these results suggest that exploration for epithermal precious metal deposits should include basal island arc tholeiite terranes

origin ore forming fluid evolution and timing of the logrosan sn w ore deposits central iberian zone spain the logrosan sn w ore deposits in the metallogenic sn w province of the european variscan belt consist of endo and exogranitic greisen type and quartz cassiterite veins associated with a s type granite mineral characterization fluid inclusion study isotope geochemistry and ar ar geochronology have been combined in order to reconstruct the conditions for sn w mineralization the endo and exogranitic mineralization must have been developed in a relatively long lived system 308 303 ma during or soon after the emplacement of the logrosan related granite at ca 308 ma the mineralizing fluids are characterized by complex aqueous and volatile h2o n2 co2 ch4 nacl fluid inclusions microthermometry and raman analyses indicate that fluid composition evolved from n2 ch4 to n2 rich followed by co2 rich fluids with varying amounts of h2o the presence of n2 and ch4 suggests the interaction with fluids derived from the nearby metasedimentary host rocks a model of host rock interaction assimilation and mixing of metamorphic and magmatic fluids resulting in change of the redox conditions is proposed for tin deposition later sulfide minerals were precipitated as a result of pressure and temperature release

dynamic response of soil pile structure system subjected to lateral spreading shaking table test and parallel finite element simulation this paper investigates the dynamic response of soil pile structure interaction spsi system behind a quay wall in liquefiable soil and laterally spreading ground through both large scale shaking

geology and geochemistry of sulfide mineralization underlying the pueblo viejo gold silver oxide deposit dominican republic the large pueblo viejo oxide gold deposit was developed by weathering of a gold quartz pyrophyllite deposit that formed during sedimentation in a small basin in the upper part of the los ranchos formation one of the oldest volcanic units in the greater antilles the basin is floored by conglomerates and agglomerates which grade upward into standstones and carbonaceous sediments that include chert with thin pyrite layers plant fossils which are common in the carbonaceous sediments indicate that the basin was near a land mass the mineralized zone is roughly funnel shaped and expands to its maximum horizontal dimensions in the carbonaceous sediments the lower part of the funnel tube contains alunite and diaspore pervasive pyrophyllite alteration makes up most of the overlying tube and upper part of the zone and locally extensive silicification makes up the top of the funnel supergene kaolinite is present in the upper part of the funnel metallic minerals consisting mostly of pyrite are found as disseminations layers and veins with base and precious metal values being highest in the veins veins are most common in the carbonaceous sediments and diminish in abundance downward into the coarser clastic units the veins contain abundant pyrite sphalerite and quartz minor barite enargite and pyrophyllite and traces of electrum argentite colusite tetrahedrite tennantite geocronite galena and tellurides containing gold silver and copper there is a strong correlation between au and zn in the upper parts of the mineralized zone and the au ag ratio which averages 1 7 decreases slightly with depth au is in electrum in the lower part of the mineralized zone and partly in tellurides in the upper part fluid inclusions indicate that fluids in the veins were very dilute boiled at least locally and reached temperatures of 130 degrees to 190 degrees c pyrophyllite stability requires minimum temperatures of about 260 degrees c for the hydrothermal system isotopic data indicate that most of the sulfur in the mineralization was derived from seawater whereas the strontium and lead came from the los ranchos formation which probably also supplied the precious metals the pueblo viejo system is similar to other gold quartz pyrophyllite deposits except that it contains no known mineable vein orebodies and instead contains numerous narrow closely spaced irregular veins that can be mined by bulk methods these veins are thought to have formed by hydraulic fracturing of the carbonaceous sediments caused by fluid pressures as the hot spring system developed the size and shape of the mineralized system at pueblo viejo resemble active hot spring systems such as wairakei new zealand and its environment of formation probably resembled that of the quaternary volcano chain which crosses lake managua in nicaragua

diffusion of osmium in pyrrhotite and pyrite implications for closure of the re os isotopic system abstract in order to better constrain the extent to which common sulfide minerals will retain their osmium isotopic composition subsequent to crystallization we have conducted experiments to quantify the diffusion behavior of osmium in pyrite and pyrrhotite experiments consisted of either 1 isothermal soaking of diffusion couples consisting of natural pyrite or pyrrhotite crystals packed against powdered os bearing fe sulfide or 2 relaxation of initially high near surface osmium concentrations produced in the latter experiments pyrite only osmium penetration into samples was characterized by depth profiling using rutherford backscattering spectroscopy rbs pyrite or electron microprobe analyses across sectioned run products pyrrhotite results of the first type of diffusion experiment involving pyrite show only limited osmium penetration into sample surfaces with the extent of penetration uncorrelated with run duration images of pyrite samples using atomic force microscopy show roughening of initially smooth surfaces as a consequence of step formation and suggest that osmium incorporation into the near surface occurred by solute uptake during step growth and not by volume diffusion prolonged 1000 h relaxation experiments revealed no additional osmium penetration into pyrite surfaces and based on the depth resolution for rbs a maximum diffusion coefficient of 2 5 10 23 m2 s at 500 c was calculated experiments involving pyrrhotite over the temperature range of 950 1100 c showed extensive osmium uptake and osmium concentration gradients that conform with fickian diffusion behavior we found that pyrrhotite fe s could be varied by changes in the composition of the starting material and osmium source and over the range of fe s produced in experiments molar fe s 0 83 0 90 we observed no systematic variation in the osmium diffusion coefficient diffusion coefficients measured parallel to the a crystallographic axis were on average 1 4 higher than values measured parallel to c and regression of the c axis data yielded the arrhenius relation d t 1 31 0 16 10 5 m 2 s exp 211 5 14 7 kj mol rt the application of these diffusion data to simple models of diffusive exchange during static or polythermal time temperature histories is used to assess the conditions under which radiogenic osmium will be retained during isothermal annealing calculations indicate that the cores of millimeter sized spherical pyrrhotite crystals undergoing diffusive exchange with an external osmium reservoir will have their initial compositions perturbed in 0 5 ma at temperatures exceeding 400 c pyrite undergoing the same process at 500 c requires in excess of 10 ma before crystal cores are affected the relatively short core retention time scales for pyrrhotite indicates that this mineral may be prone to isotopic resetting following relatively brief crustal thermal events thus possibly accounting for the scatter that commonly occurs in re os isochrons generated from massive sulfide samples calculated closure temperatures tc for osmium exchange in pyrrhotite yielded values of 300 400 c for grain sizes ranging from 10 to 1000 m these values of tc are similar to those calculated for ar retention in biotite and considerably lower than for sr in apatite and plagioclase for example such low closure temperatures for pyrrhotite suggest this mineral will date the final stage in the cooling of a magmatic system and possibly be susceptible to open system osmium exchange in the presence of late stage hydrothermal fluids this latter result infers that caution be applied when interpreting elevated initial osmium isotopic ratios as a product of crustal assimilation at the magmatic stage

genesis of the xiaolonghe quartz vein type sn deposit sw china insights from cathodoluminescence textures and trace elements of quartz fluid inclusions and oxygen isotopes abstract quartz textures revealed by scanning electron microscope cathodoluminescence sem cl images suggest that quartz in the xiaolonghe sn deposit formed in at least three fluid episodes quartz q1 in the pre ore silicification zone has homogeneous texture high cl intensity and high ti content 19 53 ppm fluid inclusions hosted in q1 are vapor rich v1 type and homogenized as supercritical fluid at 570 c quartz q2 in the syn ore topaz cassiterite quartz veins has lower cl intensity and is characterized by euhedral growth zones with lower ti content 1 3 12 ppm fluid inclusions hosted in q2 topaz and cassiterite are liquid rich fluid inclusions of moderate salinity 15 wt nacl equiv l1 type which homogenized at 423 c the post ore quartz q3 closely associated with sericitization of topaz generally crosscuts q2 and has dark cl intensity and much lower ti concentration the upper limits of t p conditions of pre ore and syn ore stage are constrained by the intersection of nacl h2o fluid inclusion isochores and ti in quartz isopleths and the lower limits are based on microthermometry results of fluid inclusions combined with the 18ofluid value 8 3 of q1 it indicates that the pre ore supercritical fluid was directly exsolved from a granitic magma at t 570 600 c and p 0 70 0 77 kbars corresponding to a maximum depth of 2 8 km under lithostatic pressure the syn ore subcritical fluid 8 0 18ofluid 6 3 mixed with some meteoric water was under 423 450 c 0 32 0 45 kbars the transition from the pre ore supercritical fluid to the syn ore subcritical fluid indicates boiling condition probably at 512 c 0 62 kbars which was likely caused by hydraulic fracturing under high pressure both the fluid boiling and fluid mixing contribute to the cassiterite precipitation in xiaolonghe sn deposit in the post ore stage the coexisting s type and v2 type fluid inclusions in q3 indicates a second fluid boiling at 269 c 0 05 kbars which was probably caused by decompression due to rapid denudation of the overlain strata the low salinity 5 5 wt nacl equiv l2 type fluid inclusions hosted in fluorite homogenized at 199 c and

the role of greisenization in cassiterite precipitation at the east kemptville tin deposit nova scotia the role of fluid rock leucogranite interaction in forming the greisen hosted tin cu zn ag deposit at east kemptville nova scotia was investigated by evaluating compositional and mineralogical changes in a representative zoned greisen and by using this information to estimate physicochemical changes in the fluid rock system at each step of the alteration a large sample comprising one side of a symmetrically zoned greisen was cut into 1 5 cm wide slabs and each slab was analyzed for its major and trace element content the results of these analyses were used to calculate the modal mineralogy of each slab which in conjunction with petrographic observations revealed two main alteration zones first or distal to the vein the leucogranite was converted to a quartz sericite greisen through the replacement of albite by muscovite this alteration specifically the dissolution of albite created some porosity closer to the vein the neoformed muscovite was converted to topaz and quartz creating a quartz topaz greisen pyrite sphalerite and cassiterite precipitated in the earlier created pore space mass balance calculations show that during alteration almost all major elements including aluminum were mobile only silicon was essentially immobile because the fluid was saturated with quartz due to earlier interaction with the leucogranite the alteration of the leucogranite resulted in a quantitative removal of the alkalies mg and mn and an addition of fe s f zn and sn the difference in the modal mineralogy of each pair of adjacent slabs was used to quantify mineralogical changes in the two main alteration reactions responsible for the observed zonation variations in the molar abundances of species in solution were evaluated by balancing the alteration reactions and by estimating the water rock ratios at each step of the alteration using oxygen isotope data the study indicates that there was an increase in the ph of the fluid and a decrease in f sub o 2 during alteration and that these changes were most important close to the vein cassiterite deposition occurred contemporaneously with the alteration of muscovite to topaz and quartz and is interpreted to have been caused by the sharp increase in ph that accompanied this reaction changes in f sub o 2 and cl super acted against cassiterite precipitation but were apparently insufficient to prevent its saturation

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

two stage gold mineralization of the axi epithermal au deposit western tianshan nw china evidence from re os dating s isotope and trace elements of pyrite the axi gold deposit is one of the largest epithermal deposits in northwestern china and is characterized by multistage generations of pyrite associated with gold mineralization genetic models for superjacent epithermal au and porphyry cu systems involve either contemporaneous or episodic mineralization implying different metal sources and ore forming events nine pyrite separates from disseminated ores associated with pyrite sericite quartz alteration in the axi deposit yield a re os isochron age of 350 10 ma mswd 5 1 initial 187os 188os ios 0 20 0 11 this age likely reflects a mixed contribution of two subtypes of disseminated pyrite py1 based on zoned pyrite crystals the isochron age of 353 6 ma mswd 1 6 ios 0 107 0 021 n 6 excluding samples with pyrite cores overlaps previous ages for andesite from the dahalajunshan formation ca 356 ma indicating that the early mineralization event occurred shortly after the formation of host rocks ca 353 ma pyrite from disseminated ores shows little variation of sulfur isotopic compositions 2 9 to 4 0 and has high cu co ni and v contents which favors a magmatic hydrothermal origin pyrite grains from gray quartz veins yield a younger re os isochron age of 332 8 ma mswd 0 22 n 4 vein hosted pyrite shows characteristics of a mantle derived magma source ios 0 171 0 024 34s 0 10 3 10 which result from the intrusion driven convective hydrothermal circulation accompanying fluid exsolution and metal remobilization from basement and wallrocks our data demonstrate that the axi gold deposit was formed during two temporally separated hydrothermal events this model of ore formation may apply to other epithermal porphyry deposits within the axi tawuerbieke district disseminated au and porphyry style au cu mineralization occurred shortly after magmatic activity 356 353 ma whereas epithermal style au mineralization occurred at ca 332 ma

re os dating of molybdenite from the pueblo viejo au ag cu and douvray cu au districts hispaniola re os dating of three samples of hydrothermal molybdenite collected from the pueblo viejo au ag cu district 5 5 moz gold past production 16 2 moz proven plus probable gold ore reserves yields ages of 112 1 0 4 112 0 0 4 and 111 5 0 4 ma these re os dates confirm an early cretaceous age for mineralization coeval with tholeiitic intraoceanic island arc volcanism and in particular with an episode of felsic magmatism and extension across the early cretaceous arc 110 118 ma re os dating of a sample of hydrothermal molybdenite collected from the douvray porphyry cu mo deposit with inferred resources of 1 257 mlb cu 0 276 moz au 6 84 moz ag and 4 367 tons mo yields an age of 93 3 0 3 ma coeval with calc alkaline magmatism along the greater antilles island arc

re os dating of chalcopyrite from selected mineral deposits in the kalatag district in the eastern tianshan orogen china the kalatag cu zn au district contains a number of economically important cu deposits in eastern tianshan in xinjiang nw china due to the lack of precise mineralization ages the metallogenesis of this area has long been a matter of debate in this study chalcopyrite re os isotope methods are used to date the south meiling cu zn and hongshi cu deposits in the eastern part of kalatag area the south meiling cu zn deposit is hosted in volcanic sedimentary rocks of the late ordovician to early silurian daliugou formation the deposit consists of two parts a concordant massive sulfide ores and discordant vein type ores located in the footwall strata the principal ore minerals are pyrite chalcopyrite sphalerite minor tetrahedrite galena and pyrrhotite gangue minerals include quartz sericite and barite and minor chlorite plagioclase and carbonate minerals the hongshi cu deposit represents a hydrothermal vein system hosted in the mafic volcanic rocks of daliugou formation the orebodies are associated with quartz veins and controlled by subsidiary faults of the kalatag fault the ore forming process can be divided into the early middle and late stages and is characterized by quartz pyrite quartz chalcopyrite pyrite and quartz carbonate gypsum veins respectively re os analyses of chalcopyrite from the south meiling cu zn deposit yield an isochron age of 434 2 3 9 ma and initial 187os 188os ratio of 0 647 0 098 mswd 0 59 re os analyses of chalcopyrite from the hongshi cu deposit yield an isochron age of 431 8 2 7 ma and initial 187os 188os ratio of 0 165 0 075 mswd 0 77 since chalcopyrite is the primary copper mineral we interpret these isochron ages as the timing of cu mineralization based on field geology and petrographic evidence these results suggest that the re os ages presented here provide for the first time a direct constraint on an early paleozoic cu mineralization event of the eastern tianshan orogen the high initial 187os 188os ratios 0 647 0 098 ratio of 434 ma chalcopyrite from the south meiling deposit suggest that the metal was sourced from a two end member mixing of crust and mantle materials moreover we propose that the vms mineral system and hydrothermal vein system of the kalatag district were related to the south dipping subduction of the kalamaili oceanic plate during the late ordovician silurian

re os dating of low level highly radiogenic llhr sulfides the harnas gold deposit southwest sweden records continental scale tectonic events to obtain geologically meaningful and precise results on low level sulfides that are highly radiogenic blank corrections that account for the extreme difference in the os isotope composition of sample and blank are necessary and the resulting data is best plotted in 187 re 187 os space much like the approach used for molybdenites we here introduce the acronym llhr as a means of characterizing low level and highly radiogenic sulfides use of the traditional 187 re 188 os vs 187 os 188 os plot for llhr sulfides leads to large analytical uncertainties and highly correlated errors as 188 os is poorly determined and can generally be accounted for by the blank we now recognize that llhr sulfides such as those encountered at the harnas au deposit are a common occurrence and characteristic of many crustally affiliated ore systems the harnas au deposit in southwest sweden is located in the mjosa vanern mineral belt that transects from northwest to southeast the prominent geologic fabric of the sveconorwegian province including the mylonite zone the deposit is hosted in a strongly sheared and locally brecciated sulfide bearing quartz vein that crosscuts the foliation of orthogneisses belonging to the 1600 maa mal granitoid suite a 187 re 187 os isochron of 973 34 ma 2 for samples of pyrite and chalcopyrite from outcrops of the harnas alma and silvergruvan veins was obtained the harnas and subsidiary alma veins are au bearing whereas the silvergruvan 2 5 km to the southeast is not of the au bearing type four replicate analyses of an additional pyrite sample from the harnas vein yield a model age of 616 40 ma 95 c l in all samples re and 187 os concentrations are extremely low 0 35 to 7 1 and 0 005 to 0 074 ppb respectively and total common os 0 002 0 028 ppb is less than half the calculated radiogenic 187 os two samples of galena from the harnas vein yielded blank level re and os neither the 973 nor 616 ma time of mineralization is related to development of the mylonite zone at 920 ma or intrusion of the anorogenic bohus blomskog granites at 920 to 900 ma previously proposed sources for generating mjosa vanern mineral belt ore fluids an age of 973 ma for harnas alma silvergruvan suggests that sulfide deposition was associated with the waning stages 0 97 0 90 ga of the sveconorwegian grenvillian orogeny 1 15 0 90 ga postdating metamorphism and deformation that produced a regionally overthickened crust in the northern part of the sveconorwegian province the vein systems for these and numerous other small deposits in the mjosa vanern mineral belt could have resulted from regional exhumation in the late sveconorwegian with associated extension and the development of fracture systems at cooler middle to upper crustal levels in the southern part of the sveconorwegian province dominated by granulitic facies rocks no mineralization is present perhaps due only to increased exhumation and erosion that has exposed deeper crustal levels the late sveconorwegian age 973 ma records the main period of sulfide deposition for the harnas alma silvergruvan vein systems and indicates the robustness of the chronometer within tectonically complex terranes the late neoproterozoic age 616 ma records a later time of pyrite deposition probably associated with shearing and reopening of the harnas vein system because the au mineralization at harnas has been described as associated with shearing and occurring in fracture fillings in early pyrite we suggest that part or all of the au mineralization could have been introduced at 616 ma during reactivation of the vein system the 616 ma age for pyrite suggests a previously unrecognized and much younger mineralizing episode in the harnas region most likely reflecting continental scale extension and the late neoproterozoic opening of the iapetus ocean

how do metals escape from magmas to form porphyry type ore deposits abstract many precious and base metals cu au ag mo w sn in porphyry type deposits are extracted from a granitic to granodioritic silicate melt and transported by magmatic hydrothermal fluids to the site of ore deposition metals abundance increases from some ppb in the melt to in ore bodies assuming a unique magmatic source for metals it implies an exceptional combination of enrichment process acting over up to 4 orders of magnitude previous models of magma differentiation and hydrothermal circulations omitted to consider the role of metal segregation during magma chamber evolution models for the formation and evolution of intrusions have recently shifted from the so called melting storage assimilation homogenization mash paradigm basically steady state to the mantle melting segregation ascent emplacement m m sae paradigm dynamic and discontinuous in time successive magma injections of variable compositions progressively build the magma chamber this is supported by field relations e g cross cutting dykes and stocks textures e g partially resorbed enclaves or mineral fabrics geochemistry e g hybridization signatures and age dating aswell as istopic studies as melt crystallizes and forms a mush 50 crystals volatiles also exsolve forming a magmatic volatile phase mvp while melt motion slows down metals partition between the three phases melt crystals and mvp they generally prefer the mvp owing to more favorable partition coefficients this is indicated by metal content in coeval melt and fluid inclusions with homogenization temperatures above 600 c or in volcanic fumaroles here by simulating the physical interactions between the three phases we suggest a model of fluid sparging during which metals segregate towards the mvp by diffusion and are further transported by advection as metal complexes the model also provides estimates of metal enrichment an undimensional peclet number rules the competition between diffusion and advection basically scaling with respect to the inverse of the product of melt viscosity by metal diffusivity d the threshold value of the peclet number between diffusion and advection is roughly 10 9 fast diffusive metals au cu ag w readily diffuse from silicate melt and towards bubbles of the mvp to escape the mush through tubular structures the mvp must overcome a critical gas saturation level about 20 vol usually reached after several magma injections advection then takes over and transports the metal enriched mvp towards the top of the magma chamber this leads to nearly coeval 1 separation between a high salinity liquid phase and a low salinity vapor phase 2 fluid rock interactions resulting in potassic advanced argillic and phyllic alterations and 3 metal deposition the metal enrichment scales as the ratio between partition coefficient i e related to the gradient in chemical potential diffusivity i e related to the gradient of concentration and melt viscosity i e related to the gradient of momentum the rates at which all such gradients relax determe metals enrichment inducing chemical and physical instabilities leading to a cyclic process the whole cycle also encompasses the case of a partial non completed full enrichment yielding to barren intrusions a tentative model generalizes the sparging fluid model to other metal deposits linked to an intrusion such generalization should be interpreted as predicting metal enrichment by 3 4 orders of magnitude rather than predicting an exact value

hydrothermal alteration and mineralization in the neves corvo volcanic hosted massive sulfide deposit portugal i geology mineralogy and geochemistry the neves corvo volcanic hosted massive sulfide deposit is one of the largest 300 mt and richest known deposits of the iberian pyrite belt the deposit is unique because of its extremely high cu and sn grades 45 mt at 6 cu plus 4 5 mt at 12 cu and 2 2 sn more than 300 000 metric tons t of tin metal is contained in several types of tin mineralization that grade from 500 ppm to 60 percent sn the deposit consists of five orebodies including corvo the focus of the present study the volcanic volcaniclastic and sedimentary lithofacies that directly host the neves corvo mineralization consist of a rhyolitic dome cryptodome hyaloclastite complex facies interpretation indicates that volcanic activity occurred at moderate water depth below storm wave base in variably subsiding basins of different orders several syn and postore modification events included gravity driven mass transport processes and subsequent low angle thrusting and asymmetric detachment folding which shaped the present deposit the ore geology and geochemistry and the textural mineralogical and geochemical aspects of the ore forming process in the corvo orebody collectively suggest that ore formation resulted from a long lived hydrothermal system including two main mineralizing events an early stage of stringer and massive cassiterite deposition and a subsequent episode of massive sulfide ore generation two spatially independent stockworks fed these genetically related mineralizing systems the early deposition of stringer and massive cassiterite ores took place almost exclusively in the tin corridor a structural alignment bounded by synvolcanic faults textural analysis and geochemical data both indicate minimal fluid rock interaction during ascent of the tin bearing fluid the massive and semimassive cassiterite ores at corvo most likely formed by direct venting into seawater and or emplacement in water laden unlithified sediments and early hydrothermal products that mantled the footwall volcanic sequence stringer and massive cassiterite precipitation is thought to have been a product of a short lived episode in the overall ore forming system the vein filling mineral assemblage in the cassiterite stockwork quartz cassiterite pyrite donbassite kaolinite chamosite coupled with whole rock and mineral geochemical data indicate that the tin bearing fluid had a low ph and relatively high temperature 380 c the massive sulfide related hydrothermal alteration in corvo is essentially strata bound the permeability contrasts in the uppermost portion of the footwall succession played an important role in controlling the fluid flow the hydrothermal alteration is zoned and consists of an inner chlorite donbassite quartz sulfide sericite core that grades outward into successive enveloping k sericite quartz sulfide and na sericite quartz sulfide halos textural evidence from the mine to the microscopic scale and mass balance considerations indicate that extensive silicate replacement in the coherent volcanic rocks of the footwall sequence and disseminated replacement mineralization in the uppermost volcaniclastic and or sedimentary units were major mechanisms of massive sulfide deposition at corvo alteration mineralogy and geochemistry indicate that the neves corvo ore fluids were hotter and more acidic than typical ore forming fluids of the iberian pyrite belt the geochemical characteristics of the tin and copper mineralization also differ from the ores of typical deposits of the iberian pyrite belt and imply the involvement of additional metal sources possibly magmatic in the ore forming system copper enrichment due to mechanical and fluid assisted tectonometamorphic remobilization processes accounts for the formation of extremely high grade ore shoots in the deposit

40ar 39ar dating of alunite from the pueblo viejo gold silver district dominican republic new 40 ar 39 ar ages for alunite from the moore and monte negro deposits in the pueblo viejo district as well as from a newly discovered alunite bearing zone on loma la cuaba west of the known deposits are reported here the ages range from about 80 to 40 ma with closely adjacent samples exhibiting very different ages interpretation of these results in the context of estimated closure temperatures for alunite and the geologic and tectonic evolution of hispaniola does not lead to a simple conclusion about the age of mineralization the simplest interpretation that mineralization was caused by a buried late cretaceous 80 ma intrusion is complicated by lack of intrusions of this age in the area and absence of alteration in overlying limestone the alternative interpretation that mineralization was formed during early cretaceous 110 ma magmatism and that the 40 ar 39 ar ages were completely reset by late cretaceous thrusting is complicated by a lack of information on the timing and thermal effects of thrusting in central hispaniola alunite studies have yielded similar unclear results in other pre cenozoic ore systems notably those of the lachlan fold belt in australia

how long can a hydrothermal system be sustained by a single intrusive event published numerical calculations show that the convective systems which produce near surface geothermal systems or ore deposits are likely to cool their intrusion heat source in at most a few tens of thousands of years even if the intrusion is large generally hydrothermal circulation near surface geothermal activity and magmatic intrusion should be closely tied in time and space long lived approximately 1 m y hydrothermal activity normally suggests multiple pulses of intrusion with associated pulses of hydrothermal circulation however if the permeability of the intruded environment is just above that which allows convection and the volume of the intrusion is very large calculations presented here show that a single episode of intrusion can sustain hydrothermal circulation and near surface geothermal activity for approximately 800 000 yr for a deep sill heat source these unusually long lived hydrothermal systems can vent through a few very widely separated discharge sites and have the potential to produce isolated massive sulfide deposits of unusually large size

ages and isotope evolution of the agua rica cu au porphyry epithermal deposit nw argentina abstract the link between porphyry epithermal deposits and continental arc magmatism is widely accepted but in flat slab settings the source of metals is still debated the central andes region hosts numerous important mineral deposits within the flat subduction zone including the world class agua rica cu au mo porphyry epithermal deposit which is associated with the farallon negro volcanic complex the suite of mineralization at agua rica includes a porphyry cu phase an associated epithermal assemblage and a supergene enrichment overprint the main mineralization is considered to be related to the trampeadero and seca norte dacite porphyry intrusions for which u pb shrimp zircon ages are 6 09 0 17 and 5 81 0 32 ma to 5 41 0 25 respectively rhenium os dating of pyrite from the trampeadero porphyry yielded an isochron with an age of 5 85 0 42 ma and molybdenite yielded a model age of 5 61 0 03 ma the seca norte body was responsible for the main porphyry style mineralization while the older trampeadero porphyry served as a host rock magmatic hydrothermal activity at agua rica commenced at approximately the same time as it was ending in other parts of the volcanic complex pb isotope signatures of sulfide samples from agua rica indicate a significant addition of crustal material to a mantle source neogene magmatism in the area is likely related to the subduction of the juan fernandez ridge which was subjacent to the deposit by the time of the porphyry intrusions upper crustal mash mixing assimilation storage and homogenization in the melting zone above the slab is inferred as the source of the shallow magma reservoir beneath the farallon negro volcanic complex

seismic lateral response of piles in liquefying soil soil liquefaction is one of the major factors affecting the behavior of piles founded in seismically active areas although methods are available for seismic analysis of pile foundations in many of them the supporting soil is assumed to be an elastic material here a numerical model is presented which takes into account the reduction of soil stiffness and strength due to pore pressure generation and subsequent soil liquefaction in addition to the material nonlinearity results obtained from the new method are compared with centrifuge test data and show excellent agreement with the observed pile behavior during these tests to investigate the effects of soil liquefaction on the internal pile response a parametric study is carried out for a range of material and geometric properties of the pile and surrounding soil the effect of the nature of the earthquake on pile performance has been studied using 25 earthquake records scaled to different acceleration levels it is shown that the arias intensity an

age of the los ranchos formation dominican republic timing and tectonic setting of primitive island arc volcanism in the caribbean region this study reports u pb ages for zircons from the los ranchos formation which is part of the primitive island arc sequence the oldest volcanic rocks in the greater antilles zircons were analyzed from three samples quartz porphyry quartz keratophyre from the lower part of the formation quita sueno member fragmental quartz porphyry from the upper part of the formation pueblo viejo member and the cotui quartz diorite stock that intrudes the lower part of the formation the lower part of the los ranchos formation represented by the quita sueno sample formed at either 113 9 0 8 or 118 6 0 5 ma depending on interpretation of the data whereas the upper part represented by the pueblo viejo sample formed ca 110 9 0 8 ma the cotui stock rd 73 601 was emplaced ca 111 8 0 6 ma or 112 9 0 9 ma depending on whether eight grains reflect subtle inheritance these results show that the los ranchos formation was emplaced during the aptian albian transition that the cotui stock could have supplied magma to the volcanic sequence and fluids to the pueblo viejo gold silver deposit in the upper part of the formation and that carbonaceous sediments in the upper part of the formation formed at the same time as ocean anoxic event 1b paquier caribbean plate tectonic models involving invasion of anomalous pacific crust into the caribbean region appear to agree best with this age because they provide a mechanism for the change from primitive island arc pia to calcalkaline magmatism and account for the restricted ocean circulation necessary to generate regional anoxic conditions

age and source of the kure odemis arsenopyrite gold mineralization menderes massif turkey determined by re os he isotopes abstract the menderes massif mm is considered to be one of the principal regions hosting vein type quartz arsenopyrite orogenic gold deposits and occurrences in turkey gold mineralizations in the mm can be grouped into i schistosity conformable e trending veins and ii shear controlled nw trending veins arsenopyrite is one of the major gold bearing minerals in these deposits or occurrences rhenium osmium isotopic dating of two types of arsenopyrite from the schistosity conformable and vein type kure odemis gold deposit has yielded two groups of model ages maximum ages at 557 574 ma and 246 250 ma respectively the data suggested that the quartz arsenopyrite gold deposit formed in the neoproterozoic and early triassic with the former and the latter corresponding to pan african compressional orogenesis and palotethys rifting respectively fluid inclusions in kure arsenopyrite have 3he 4he ratios of 0 08 0 09 ra ra 1 39x10 6 the 3he 4he ratio of air being within the range of middle to upper crustal values a minor helium contribution of mantle fluids to the kure gold deposit is possible because the 4he concentrations in arsenopyrite are enriched 170 to 9520 times relative to argon and typical atmospheric values indicating that contribution of atmospheric he to the mineralizing fluids is negligible and 0 08 0 09 ra is slightly above typical crustal 3he 4he ratios arsenopyrite yields relatively non radiogenic initial os isotopic compositions also indicating possiblecontribution from mantle fluids carbonic fluid inclusion type 2 h2o co2 nacl ch4 in quartz of nw trending veins at kure are gas liquid hydrate crystal rich and their homogenization temperatures th range from 244 to 387 c salinity values range from 0 2 to 5 7 wt nacl equiv the homogenization temperatures th of aqueous fluid inclusions type 1 h2o nacl in quartz from nw trending veins at kure vary between 237 and 358 c whereas salinity values range from 1 7 to 7 7 wt nacl equiv quantitative epma spot analyses on arsenopyrite minerals have shown that as concentrations in ew trending and nw trending veins range from 32 5 to 33 8 and 32 3 33 8 respectively based on a phase diagram for the fe as s system along with the arsenopyrite geothermometer the ranges of temperature and corresponding logf s2 at which arsenopyrite is in equilibrium with pyrite are between 380 and 480 c and 7 4 and 4 3 for apy 1 respectively these values are between 390 and 475 c and 7 0 and 4 5 for apy 2 respectively

kinematic pile bending during earthquakes analysis and field measurements the passage of seismic waves through the soil surrounding a pile imposes lateral displacements and curvatures on the pile thereby generating kinematic bending moments even in the absence of a su

seismic response of end bearing piles a very simple analysis of dynamic soil pile supported mass interaction is presented as an aid to understanding pile foundations behaviour during earthquakes the equilibrium equations of the soil and pile movements during seismic motions are established and the response of the soil pile system is obtained as a function of the existing frequency for simplicity the analysis was based on winkler s model although the same procedure can be applied using a more refined model the effect of the supported mass is studied the natural frequency of the system is obtained and some practical design considerations are presented a method for considering group effects is also presented

contrasting fluid behavior during two styles of greisen alteration leading to distinct wolframite mineralizations the echassieres district massif central france abstract the echassieres district of central france hosts diverse magmatic and magmatic hydrothermal deposits of rare metals mostly related to the well known beauvoir granite tungsten mineralization crops out at three distinct wolframite occurrences the two most important of which are related to two distinct magmatic bodies emplaced ca 335 and 310 ma monnier et al 2019 the mineralization occurred at 335 ma formed during a hydrothermal episode marked by precipitation of topaz replacing quartz in a stockwork system and as veinlets in the surrounding schist fluid inclusions in topaz and quartz display similar features i e all have low salinity contain significant amount of licl display constant liquid vapor ratios and homogenized within a narrow temperature range th 380 c no evidence for fluid pressure variations was observed and temperature decrease is considered to be the main cause for wolframite deposition the younger w mineralization is related to greisenizing fluids that altered the beauvoir granite and generated several quartz topaz and apatite veins all greisen related fluid inclusions display low salinity however th are spread from ca 190 to 400 c and several populations exhibit heterogeneous liquid vapor ratios while others consist of only vapor rich fluid inclusions respectively these populations are interpreted to have been trapped during boiling or flashing vaporization of the fluid in contrast with the other regional veins flashing was particularly intense in the mazet veins which host the bulk of the last wolframite generation consequently it is proposed that flashing is the key factor that triggered w precipitation this work highlights the role of two physical parameters pressure and temperature whose variations played a preponderant role on wolframite mineralization it documents in depth an example of greisen fluid evolution providing critical information on w behavior in orthomagmatic fluids and on greisen related rare metal deposits

modeling fluid rock interaction during greisenization at the east kemptville tin deposit implications for mineralization interaction between a tin bearing greisenizing fluid and a leucogranitic rock was modeled in order to evaluate the possible role of alteration induced changes in fluid chemistry in cassiterite deposition the interaction was modeled using simple titration and multiple pass fluid flow models with the program chiller modified to permit calculations at 450 c and 4 0 kb the compositions of the mineralizing fluid and the unaltered leucogranite were based respectively on analyses of fluid inclusions and whole rock chemistry of samples from the east kemptville greisen hosted tin deposit nova scotia the starting fluid contained 4 85 m cl 3 7 m na 0 53 m fe and minor k si f and sn and was at a ph of 3 0 while the leucogranite contained 35 wt quartz 29 wt albite 19 wt muscovite and 17 wt k feldspar in both models the calculations show that with increasing alteration k feldspar was the first mineral consumed and that this was followed by replacement of albite by muscovite with further alteration muscovite was replaced by topaz and pyrrhotite and cassiterite precipitated in quartz topaz rocks in the most altered rocks only topaz and quartz are present these changes accurately reproduce those determined for natural samples at east kemptville however only the multiple pass fluid flow model predicts the changes in fluid inclusion composition the multiple pass fluid flow model quantified changes in fluid composition as a function of its interaction with the wall rock and thus enabled us to assess better the factors that controlled cassiterite precipitation important conclusions of the model are that the fluid and the rock equilibrated at each stage of the alteration and the water rock ratio remained constant across the alteration halo we further concluded that phases precipitated close to the vein in an earlier stage of the alteration were re dissolved with evolution of the mineralizing system in particular re dissolution of cassiterite caused an increase in the concentration of sncl in the fluid as a result cassiterite saturated at a lower ph and the chemical potential of sncl increased away from the vein this could in turn explain the low tin grades at east kemptville

quantitative analysis of tin and tungsten bearing sheeted vein systems several methods are investigated for the quantitative analysis of a range of sn w sheeted vein systems from southwest england and spain the methods are based on fractal concepts and include the measurement of vein thickness and spacing distributions and the development of a multifractal interval counting method equivalent to box counting in two dimensions the results indicate that sets of subparallel veins are generally distributed randomly or with only slight clustering and develop from fracture systems in which the spacing of veins is homogeneous the opening of the veins is much more heterogeneous suggesting localization of subsequent deformation and flow this is especially true in mineralized areas and together with power law distributions of vein thickness can be used to characterize mineralized systems new data presented in this paper suggest that fracture evolution may play a fundamental role in defining the location and style of sn w mineralization observed greisen dominated and disseminated sn w systems develop where the initial fracture system dominates the fluid flow regime whereas sheeted vein systems are best developed where stress induced critical behavior of flow in fracture networks controls the permeability and fluid flow of the system

pueblo viejo high sulfidation epithermal gold silver deposit dominican republic a new model of formation beneath barren limestone cover a discussion sillitoe et al 2006 suggest that the pueblo viejo au ag deposit is younger than its early cretaceous los ranchos formation host rocks this interpretation contrasts with our earlier observations that the mineralization is coeval with the los ranchos formation although a younger age would allow pueblo viejo to be conveniently grouped with many other high sulfidation deposits in a subaerial calc alkaline setting evidence for it conflicts with geologic observations in and around the deposit the new interpretation of the age of mineralization depends largely on the contention that the hatillo limestone which overlies the los ranchos formation was replaced along its basal contact by silica and magnetite that are coeval with pueblo viejo mineralization in their figure 2 p 1429 sillitoe et al show two silicified and iron oxide bearing zones along the poorly exposed base of the hatillo limestone outliers one of these zones is along the southern edge of the pueblo viejo mine where mine workings and exploration drill holes immediately south of the contact provide good exposures in this area the contact which is tectonized locally ranges from a basal conglomerate with silicified cobbles to calcareous sandstone siltstone mudstone with abundant marine fossils silicified cobbles require that silicification preceded deposition of the hatillo limestone similarly carbonaceous sediments containing silicified boulders and cobbles and underlying fragmental rocks with clasts exhibiting different alteration assemblages are widespread in the mine area russell and kesler 1991 fig 3 sillitoe et al 2006 do cite one outcrop containing veinlets of iron oxide limonite with marginal silicification russell and kesler 1991 p 210 211 as evidence of silicification and iron oxides in the basal few meters of the hatillo limestone they acknowledge however that we interpreted these features as paleo supergene which they clearly are furthermore they are

chronology of the pueblo viejo epithermal gold silver deposit dominican republic formation in an early cretaceous intra oceanic island arc and burial under ophiolite the pueblo viejo deposit production to 1996 166 t au 760 t ag is located in the dominican republic on the caribbean island of hispaniola and ranks as one of the largest high sulfidation acid sulfate epithermal deposits reserves in 2007 635 t au 3 648 t ag one of the advanced argillic ore bodies is cut by an inter mineral andesite porphyry dike which is altered to a retrograde chlorite illite assemblage but overprinted by late stage quartz pyrite sphalerite veins and associated low grade au ag zn cd hg in as se and te mineralization the precise tims u pb age 109 6 0 6 ma of the youngest zircon population in this dike confirms that the deposit is part of the early cretaceous los ranchos intra oceanic island arc intrusion related gold sulfide mineralization took place during late andesite dacite volcanism within a thick pile 200 m of carbonaceous sand and siltstones deposited in a restricted marine basin the high level deposit was shielded from erosion after burial under a late albian 109 100 ma ophiolite complex 8 km thick which was in turn covered by the volcano sedimentary successions 4 km of a late cretaceous early tertiary calc akaline magmatic arc estimates of stratigraphic thickness and published alunite illite and feldspar k ar ages and closure temperatures alunite 270 20 c illite 260 30 c k feldspar 150 c indicate a burial depth of about 12 km at 80 ma during peak burial metamorphism 300 c and 300 mpa the alteration assemblage kaolinite quartz in the deposit dehydrated to pyrophyllite temperature time relations imply that the los ranchos terrane then cooled at a rate of 3 4 c ma during slow uplift and erosion

alkali metals control the release of gold from volatile rich magmas magmatic hydrothermal ore deposits are a major resource of gold volatiles exsolving from magmas rising through the earth s crust are the key agent for enrichment of gold in these deposits we report the first experimental determination of gold solubilities in the magmatic volatile phases at conditions typical of most magmas associated with gold deposits t 1000 degrees c p 150 mpa we show that gold hydrosulfide complexes supersede gold chloride complexes and more importantly that the stability of gold hydrosulfide complexes is greatly increased by the presence of minute concentrations of kc or nacl 0 1 0 5 mol kg h2o the amplifying effect of alkali chlorides on the solubility of gold in h2s bearing volatiles may explain the preferential association of many giant hydrothermal gold deposits with high potassium alkaline mafic to intermediate igneous rocks which exsolve volatiles that simultaneously contain both h2s and alkali chlorides in significant concentrations c 2010 elsevier b v all rights reserved

gold deposition by sulfidation of ferrous fe in the lacustrine sediments of the pueblo viejo district dominican republic the effect of fe c s diagenesis on later hydrothermal mineralization in a maar diatreme complex abstract the pueblo viejo district located in the cordillera central of the dominican republic contains large au ag deposits associated with acid sulfate alteration within spilites conglomerates and carbonaceous sedimentary rocks that were deposited in a maar diatreme complex much of the au mineralization occurs in pyritic carbonaceous siltstones of the pueblo viejo maar diatreme member of the cretaceous los ranchos formation pyrite is the only fe bearing phase in mineralized rock whereas siderite is the dominant fe bearing phase in siltstones distal to mineralization disseminated pyrite occurs as framboids cubes pyritohedra concretions and cement early framboids occur throughout the district au occurs as inclusions in later non framboid disseminated pyrite nfdp an occurrence that is interpreted to be indicative of contemporaneous deposition pyrite framboids exhibit a wide range of 34s cdt values 17 5 to 4 8 and are interpreted to have formed during biogenic reduction of pore water sulfate the nfdp yield restricted 34s cdt values x 5 2 s 2 4 n 43 similar to those obtained from later vein pyrite x 6 4 s 1 5 n 12 alunite and barite have 34s values ranging from 18 8 to 21 6 the interpretation that the nfdp vein pyrite alunite and barite and possibly even the framboidal pyrite share a common source of igneous sulfur is supported by the 34s data siderite occurs as concretions and cement contains abundant mg fe0 75mg0 19mn0 03ca0 02co3 and has 13c pdb and 18o smow values ranging from 2 5 to 1 1 and 14 6 to 19 5 respectively these data are consistent with the interpretation that the siderite formed in lacustrine sediments and that the carbonate in the siderite is probably methanogenic although contributions from oxidation of organic matter during biogenic sulfate reduction thermal decarboxylation of organic matter or magmatic vapor cannot be ruled out disseminated au mineralization in the sedimentary rocks formed when a hydrothermal fluid encountered reactive fe2 in diagenetic siderite the ensuing pyrite deposition consumed h2s and destabilized the au hs 2 complex leading to precipitation of au the capacity of the sedimentary rocks to consume h2s and precipitate au was controlled by the amount of non pyrite fe present as siderite the abundance of siderite was controlled by the extent of pyrite formation during diagenesis

discussion of kinematic bending of fixed head piles in nonhomogeneous soil by raffaele di laora and emmanouil rovithis abstractkinematic bending of elastic single fixed head piles in continuously inhomogeneous soil is explored in both static and dynamic regime a generalized parabolic function is employed to describe the variable shear modulus in the inhomogeneous stratum which can simulate both cohesive and cohesionless soil deposits the problem is treated numerically by means of rigorous elastodynamic finite element analyses and simplified beam on dynamic winkler foundation bdwf formulations a novel expression is proposed for the active length of a pile in inhomogeneous soil by means of kinematic interaction considerations this allows an alternative interpretation of kinematic soil pile interaction along an effective depth contrary to existing definitions in which soil response is evaluated at a specific location following this interpretation a design formula for kinematic pile head moments is derived for both static and dynamic loading a new dimensionless parameter is identified to govern dynamic pile bendin

evolution of the monte negro acid sulfate au ag deposit pueblo viejo dominican republic important factors in grade development this study was undertaken to determine the geologic factors that were important in making pueblo viejo which contains over 600 000 kg of gold in relatively high grade ore one of the few acid sulfate deposits to be mined economically on a large scale orebodies at pueblo viejo including monte negro the focus of this study are found around a maar diatreme complex that formed in the upper part of the lower cretaceous los ranchos formation ore is hosted by spilite spilite derived conglomerate and intramaar carbonaceous sandstone and mudstone regional seawater alteration of these rocks was overprinted by two stages of advanced argillic alteration both of which are associated with precious metals stage i produced deep alunite quartz pyrite and overlying kaolinite quartz pyrite assemblages and deposited gold in association with disseminated pyrite in wall rock stage ii which overprinted stage i produced deep pyrophyllite or diaspore and an overlying recrystallized silica cap pyrite or sphalerite or enargite veins that probably formed in response to hydrofracturing of the silica cap contain gold grades of as much as 100 ppm vein density and assay data show that approximately 60 percent of the gold at monte negro is in disseminated stage i ore with the remainder in stage ii veins phase equilibria and sulfur isotope thermometry show that stage i alteration took place below 260 degrees c at ph values between 2 and 3 stage ii pyrophyllite or diaspore formation occurred above 285 degrees c from a fluid with an initial ph of 1 to 1 5 while the silica caps formed below 220 degrees c geologic constraints indicate that stage i wall rock gold at monte negro was deposited by sulfidation of fe rich wall rock whereas stage ii vein hosted gold could have formed by cooling boiling or mixing with overlying ground water use of the programs solveq and chiller to evaluate the relative efficiencies of these ore forming processes confirms that sulfidation was capable of depositing disseminated stage i gold whereas stage ii vein gold was probably deposited by boiling related to pressure release during hydrofracturing and subsequent mixing with ground water these observations indicate that development of grade and tonnage at pueblo viejo was greatly facilitated by 1 the porous permeable maar diatreme complex which hosted large shallow hydrothermal cells and probably served as a conduit for rising magmatic gases 2 the presence of iron rich wall rock which caused early deposition of background disseminated gold by sulfidation and 3 later hydrothermal activity which formed impermeable silica caps that hydrofractured to create the high grade vein overprint remobilization of stage i background gold into stage ii veins might also have been an important factor in upgrading the deposits exploration for similar deposits should focus on areas of explosive volcanism in andesitic island arc terranes

a centrifuge study of the seismic response of pile raft systems embedded in soft clay a series of centrifuge tests were performed on a 4 3 pile raft system embedded in soft kaolin clay to investigate the pile bending moment and raft acceleration response under seismic excitation

kinematic pile response to vertical p wave seismic excitation an analytical solution based on a rod on dynamic winkler foundation model is developed for the response of piles in a soil layer subjected to vertical seismic excitation consisting of harmonic compressional waves closed form solutions are derived for 1 the motion of the pile head 2 the peak normal strain in the pile and 3 the group effect between neighboring piles the solutions are expressed in terms of a dimensionless kinematic response factor iv relating pile head motion and free field soil surface motion a dimensionless strain transmissibility factor ie relating pile and soil peak normal strains and a pile to pile interaction factor measuring group effects it is shown that a pile foundation may significantly reduce the vertical seismic excitation transmitted to the base of a structure

experimental evidence for the alteration of the fe3 σfe of silicate melt caused by the degassing of chlorine bearing aqueous volatiles the temporal evolution of the redox conditions undergone by degassing magmas has petrologic implications for magmatic phase equilibria we present new experimental data that demonstrate that a cl bearing magmatic volatile phase may affect the concentration and activity of ferrous iron in silicate liquid via the preferential mass transfer of fe 2 into the volatile phase the data are consistent with a model wherein the exsolution of a cl bearing volatile phase from the melt modifies the mgo feo ratio of the residual degassed melt increasing the fe 3 fe ratio of the melt degassing induced alteration of the melt may cryptically affect the phases that constitute the hypersolidus crystallizing assemblage the new results indicate that a low to moderate salinity magmatic volatile phase may contain several weight percent iron present as fecl 2 as such passive degassing over geologically plausible protracted periods has the potential to extract significant quantities of fe 2 resulting in a residual melt depleted in feo relative to fe 2 o 3 notably preferential mass transfer of fe 2 from the melt to the fluid results in self oxidation of the melt driving the oxygen fugacity of the melt across the phase boundary that demarcates the stability fields of sulfide and sulfate phases stabilizing sulfate at the expense of sulfide such a process has significant implications for the remobilization of chalcophile metals during the evolution of magmatic hydrothermal systems

the response of flexible piles to lateral loading the majority of piles encountered in practice may be regarded as flexible under lateral loading that is the induced deformations and bending moments are confined to the upper part of the pile and the overall length of the pile does not significantly affect the response of the pile the results of a parametric study conducted using the finite element method and treating the soil as an elastic continuum with a linearly varying soil modulus are presented as simple algebraic expressions these expressions are similar in form to those which arise from a winkler idealization of the soil enabling immediate estimates to be made of the active length of the pile the ground level deformations and the maximum bending moment down the pile in addition expressions are presented quantifying the effect of interaction between neighbouring piles from which the behaviour of groups of piles subjected to lateral loading may be deduced application of the solutions is demonstrated by the analysis of lateral loading