mineral and stable isotope compositions phase equilibria and 40ar 39ar geochronology from the iron skarn deposit in sangan northeastern iran abstract the sangan iron skarn deposit is located on the eastern edge of the sabzevar doruneh magmatic belt northeastern iran mineralization occurs at the contact between eocene igneous rocks and cretaceous carbonates the silicate dominant prograde skarn stage consists of garnet and clinopyroxene whereas the retrograde stage is dominated by magnetite associated with minor hematite phlogopite pyrite and chalcopyrite phase equilibria and mineral chemistry studies reveal that the skarn formed within a temperature range of 375 to 580 c and that the mineralizing fluid evolved from a hot low oxygen fugacity alkaline fluid during the silicate dominant stage to a fluid of relatively lower temperature and higher oxygen fugacity at the magnetite dominant stage the 18 o values of magnetite and garnet vary from 3 1 to 7 5 and 7 7 to 11 6 respectively the calculated 18 o h2o values of fluid in equilibrium with magnetite and garnet range from 9 8 to 11 1 and 10 1 to 14 8 respectively these elevated 18 o h2o values suggest interaction of magmatic water with 18 o enriched carbonates the high 34 s values 10 6 to 17 0 of pyrite separates from the sangan iron ore indicate that evaporites had an important role in the evolution of the hydrothermal fluid phlogopite separates from the massive ores yield 40 ar 39 ar plateau ages of 41 97 0 2 and 42 47 0 2 ma indicating that the skarn formation and associated iron mineralization was related to the oldest episode of magmatism in sangan at 42 ma eocene time marked a peak of magmatic activity and associated skarn in the post collisional setting in northeastern iran whereas oligo miocene magmatic activity and associated skarn in the urumieh dokhtar magmatic belt are related to subduction in addition skarn mineralization in northeastern and eastern iran is iron type but skarn mineralization in the urumieh dokhtar magmatic belt is copper iron and copper type

semi analytical solution for flow in a leaky unconfined aquifer toward a partially penetrating pumping well summary a semi analytical solution is presented for the problem of flow in a system consisting of unconfined and confined aquifers separated by an aquitard the unconfined aquifer is pumped continuously at a constant rate from a well of infinitesimal radius that partially penetrates its saturated thickness the solution is termed semi analytical because the exact solution obtained in double laplace hankel transform space is inverted numerically the solution presented here is more general than similar solutions obtained for confined aquifer flow as we do not adopt the assumption of unidirectional flow in the confined aquifer typically assumed to be horizontal and the aquitard typically assumed to be vertical model predicted results show significant departure from the solution that does not take into account the effect of leakage even for cases where aquitard hydraulic conductivities are two orders of magnitude smaller than those of the aquifers the results show low sensitivity to changes in radial hydraulic conductivities for aquitards that are two or more orders of magnitude smaller than those of the aquifers in conformity to findings of earlier workers that radial flow in aquitards may be neglected under such conditions hence for cases were aquitard hydraulic conductivities are two or more orders of magnitude smaller than aquifer conductivities the simpler models that restrict flow to the radial direction in aquifers and to the vertical direction in aquitards may be sufficient however the model developed here can be used to model flow in aquifer aquitard systems where radial flow is significant in aquitards a 2008 elsevier b v all rights reserved

zn he ar and sr nd isotopic compositions of the tongkeng tin polymetallic ore deposit in south china implication for ore genesis abstract the tongkeng tin polymetallic ore deposit in nandan county guangxi zhuang autonomous region southern china is the representative deposit of the largest scale in the famous dachang tin polymetallic ore field it consists of the upper tin polymetallic ores and the lower newly found zinc copper ores with the sn metal reserve of 680 000 tons average grade 1 4 500 000 tons of zn average grade 4 and 80 000 tons of cu average grade 0 2 the orebodies occur as layers and veins within the middle to late devonian siliceous rocks and carbonate rocks in this paper the isotopic compositions of zn he ar and sr nd of the tongkeng deposit have been studied systematically the results show that the isotopic composition of zn is quite homogenous with 66zn 0 22 0 34 in sphalerite samples of various colors from brown to black collected from different orebodies upper tin polymetallic and lower zinc copper ores in the tongkeng deposit it indicates that zn source mainly came from magmatic fluid as the calculated 66zn 0 42 0 54 of ore forming fluid is almost same as that of the longxianggai granite 0 41 0 55 but quite different from that of the marine carbonate average 0 91 he ar isotope study of pyrite shows that the exhalative substances might have been involved in the mineralization with 3he 4he 1 2 ra 2 5 ra in the upper tin polymetallic ores and 3he 4he 0 8 ra 1 9 ra in the lower zinc copper ores in the tongkeng deposit which is different from that of the longxianggai granite 3he 4he 0 7 0 8 ra but close to that of the devonian liujiang formation exhalative sedimentary sequences with 3he 4he 1 5ra the longxianggai granite has isr 0 719 in average end t 7 9 9 6 and nd model age t2dm 1 54 1 68 ga based on the geochemical characteristics of granite and sr nd and o isotopes the source rocks of the longxianggai granite may be mainly derived from the continental crust which is a typical remelted s type granite based on the results of this study and the previous data in the literature it is concluded that the mineralization in the dachang ore field is closely related to the cretaceous longxianggai granite in time and space with the main metal substances of zn most likely derived from the magmatic fluid classified into the type of post magmatic hydrothermal filling metasomatism the admixing of the early devonian spouting sediments in the mineralization was evidenced in the study of source trace and has led to the longtime dispute over the ore genesis

the early proterozoic birimian supergroup of ghana and some aspects of its associated gold mineralization abstract rocks of the birimian supergroup of early proterozoic age sm nd isochron age 2166 66 ma form part of the west african craton ghana contains the eastern portion of the birimian terrane five parallel evenly spaced several hundred kilometre long volcanic belts consisting mainly of low grade metamorphic tholeiitic lavas morb chemistry characterize the birimian supergroup of ghana the belts are separated by basins containing isoclinally folded dacitic volcaniclastics wackes and argillitic sediments as well as granitoids lavas and sedimentary rocks were deposited contemporaneously as lateral facies equivalents within the sedimentary basins various lithofacies are distinguished in the transition zone between belt volcanics and basin sediments a chemical facies occurs this is defined by cherts manganiferous and carbon rich sediments fe ca mg carbonates and sulphide mineral disseminations after their emplacement birimian lavas and sediments were folded in the course of the eburnean tectono thermal event intruded by various types of granitoids uplifted and eroded the erosion products were deposited as sediments of the tarkwaian group in long narrow intramontane grabens which formed due to rifting preferentially in the central portions of all five birimian volcanic belts tarkwaian sediments were deformed by gravity tectonics two major types of eburnean granitoids in ghana are characterized as follows basin granitoids cape coast type occur as synorogenic foliated batholiths chiefly in the central portions of birimian sedimentary basins they are peraluminous and generally granodioritic in composition belt granitoids dixcove type mostly form late orogenic unfoliated intrusions in volcanic belts they possess a metaluminous character and commonly are of tonalitic composition bongo granitoids are of post tarkwaian age and k rich in contrast to these granitoid types which have strong mantle affinities the winneba type had an archean sialic precursor a model involving small scale equidimensional parallel and contemporaneously operating convection cells in the upper mantle which caused rifting of a highly attenuated protocrust as well as linear eruptions of tholeiitic magmas is proposed recent sm nd pb pb and rb sr data of volcanic and plutonic rocks are incorporated most ghanaian birimian gold occurrences and mines are concentrated in narrow corridors of 10 15 km width in the transition zone between volcanic belts and sedimentary basins as are the chemical facies and regionally extensive shear zones at the volcanics sediment interface birimian gold in ghana is present as two major types 1 the disseminated sulphide type which is generally lithofacies controlled i e controlled by chemical sediments and to a lesser extent by selvages of gold quartz veins and 2 the quartz vein type which is exclusively structure controlled data on geochemical underground traverses across both types of gold mineralization are briefly summarized

geochemistry and origin of tin polymetallic sulfide deposits hosted by the devonian black shale series near dachang guangxi china abstract two tin polymetallic sulfide deposits hosted by the devonian black shale series of the guangxi zhuang autonomous region occur in the dachang ore field the upper devonian frasnian epoch black shale series contains the giant tongkeng changpo deposit and the middle devonian givetian epoch reef limestone contains the giant longtoushan deposit intrusive rocks occur at lame and the western part of dachang ores occur as stratified bodies large veins stockworks and zones of veinlets ores are massive banded laminated and disseminated the ores contain more than 180 different minerals the most important of which are cassiterite sulfides and sulfosalts primary laminated sedimentary sulfide ores occur at tongkeng the mean ratio of sio 2 al 2 o 3 for shale marl is 3 5 but values averaging 56 and 67 respectively for ore and chert suggest a biogenic or hydrothermal source for silica ores and country rocks are rich in sb pb zn sn and cu granites are rich in sb w zn and sn dispersed elements such as te cd se and in are abundant in ores country rocks and granites implying contributions of sedimentary and intrusive activities to the ore formation mean y ho values for the black shale series 28 and granite 31 are similar to most shales and most volcanic rocks the y ho value for reef limestone is 47 comparable to sea water devonian black shale series are slightly lree enriched on chondrite normalized plots and show small negative eu anomalies mean eu 0 56 ce 0 9 and ce anom 0 07 values suggest a shallow water deposition near the redox boundary the 34 s values of sulfides from various deposits of dachang vary with the 34 s values for lame ranging from 2 to 2 and values for tongkeng changpo ranging from 4 9 to 2 6 the highly negative 34 s values 9 5 to 11 3 of huile and kengma sulfides suggest the important role of biogenic sulfur the mean 13 c value of organic matter of devonian black shale series is 24 6 the 30 si nbs 28 values of upper devonian black chert are 0 2 0 3 indicating a sedimentary origin the dachang black chert has been dated at 124 2 ma that of luofu section at 387 18 ma implying that the rb sr isotope of dachang chert was reset during yanshan movement these results suggest that the dachang tin polymetallic sulfide deposits exemplify strongly remobilized sedimentary mineralization

semi analytical solution of flow to a well in an unconfined fractured aquifer system separated by an aquitard abstract semi analytical solutions are presented for flow to a well in an extensive homogeneous and anisotropic unconfined fractured aquifer system separated by an aquitard the pumping well is of infinitesimal radius and screened in either the overlying unconfined aquifer or the underlying fractured aquifer an existing linearization method was used to determine the watertable drainage the solution was obtained via laplace and hankel transforms with results calculated by numerical inversion the main findings are presented in the form of non dimensional drawdown time curves as well as scaled sensitivity dimensionless time curves the new solution permits determination of the influence of fractures matrix blocks and watertable drainage parameters on the aquifer drawdown the effect of the aquitard on the drawdown response of the overlying unconfined aquifer and the underlying fractured aquifer was also explored the results permit estimation of the unconfined and fractured aquifer hydraulic parameters via type curve matching or coupling of the solution with a parameter estimation code the solution can also be used to determine aquifer hydraulic properties from an optimal pumping test set up and duration

major ion chemistry of the ganga brahmaputra river system weathering processes and fluxes to the bay of bengal the ganga brahmaputra one of the world s largest river systems is first in terms of sediment transport and fourth in terms of water discharge a detailed and systematic study of the major ion chemistry of these rivers and their tributaries as well as the clay mineral composition of the bed sediments has been conducted the chemistry of the highland rivers upper reaches of the ganga the yamuna the brahmaputra the gandak and the ghaghra are all dominated by carbonate weathering ca mg and hco3 account for about 80 of the cations and anions in the lowland rivers the chambal the betwa and the ken hco3 excess over ca mg and a relatively high contribution of na k to the total cations indicate that silicate weathering and or contributions from alkaline saline soils and groundwaters could be important sources of major ions to these waters the chemistry of the ganga and the yamuna in the lower reaches is by and large dictated by the chemistry of their tributaries and their mixing proportions illite is the dominant clay mineral about 80 in the bedload sediments of the highland rivers kaolinite and chlorite together constitute the remaining 20 of the clays in the chambal betwa and ken smectite accounts for about 80 of the clays this difference in the clay mineral composition of the bed sediments is a reflection of the differences in the geology of their drainage basins the highland rivers weather acidic rocks whereas the others flow initially through basic effusives the ganga brahmaputra river system transports about 130 million tons of dissolved salts to the bay of bengal which is nearly 3 of the global river flux to the oceans the chemical denudation rates for the ganga and the brahmaputra basins are about 72 and 105 tons km yr 1 respectively which are factors of 2 to 3 higher than the global average the high denudation rate particularly in the brahmaputra is attributable to high relief and heavy rainfall

geology and genesis of the hehuaping magnesian skarn type cassiterite sulfide deposit hunan province southern china abstract magnesian skarn type tin deposits are relatively rare in the world the hehuaping cassiterite sulfide deposit in southern china having a total reserve of approximately 130 000 t of tin 50 000 t of lead and 10 000 t of zinc is identified as such type the deposit is related to the late jurassic 157 ma hehuaping medium to coarse grained biotite granite that intruded the middle devonian qiziqiao dolomite formation and the tiaomajian sandstone formation four paragenetic stages of skarn and ore formation have been recognized i prograde stage ii retrograde stage iii cassiterite sulfide stage and iv carbonate stage alteration zoning between fresh granite and unaltered country rocks can be identified the skarn are typified by mg mineral assemblages of forsterite spinel diopside tremolite serpentine talc and phlogopite the geochemistry of various skarn minerals shows a gradually decrease of mg end member and correspondingly an increase of fe and especially mn end members along the process of skarn alteration tin mineralization developed during the late retrograde stage resulted in cassiterite magnetite diopside skarn however the deposition of cassiterite occurred predominantly as cassiterite sulfide veins along fractures and interlayer fracture zones during stage iii the petrogeochemistry of hehuaping granite as well as s and pb isotopic analyses suggest that the ore forming elements have a magmatic source originated from the upper crust the h o isotopic and fluid inclusion analyses indicate that high temperature ore forming fluids in early anhydrous skarn stage stage i are also magmatic origin in comparison the retrograde fluids are characterized by relatively low salinity 2 to 10 wt nacl equiv and low temperature 220 to 300 c suggesting a mixed origin of meteoric waters with magmatic fluids the major ore forming stage iii fluids are characterized by lower temperature 170 to 240 c and salinity 1 to 6 wt nacl equiv indicating fluid mixing could be an efficient tin mineralizing mechanism meteoric waters are dominant in stage iv resulting in a further lowering of temperature 130 to 200 c and salinity 0 4 to 1 wt nacl equiv

unsteady flow to a partially penetrating pumping well with wellbore storage in a dual permeability confined aquifer abstract in this article a new model is presented for imparting unsteady flow to a partially penetrating pumping well with wellbore storage placed in double permeability confined aquifers to investigate the wellbore drawdown transient behavior in this model both the fracture and matrix systems are connected directly with the wellbore as flow pathways while comprehensively considering the crossflow between the matrix and the fractures the top and bottom boundaries are assumed to be impermeable and the outer side boundaries could be infinite subsequently laplace transformation and finite fourier cosine transformation are employed to obtain analytical solutions of the dual permeability flow model in the laplace domain the derived analytical solution is general and can be reduced to several other previous results the numerical inversion algorithm of stehfest is used to solve the wellbore drawdown in the real time domain subsequently the model is validated by comparing it with previous results groundwater flow characteristics are analyzed in detail and divided into five flow stages wellbore storage flow early radial flow quasi spherical flow crossflow between the matrix and the fractures and quasi radial flow the different flow stages show some special values on the drawdown and its derivative log log plots there is a hump dip feature in the semi logarithmic curve of the drawdown derivative which are inherent characteristic for dual permeability flow behavior the effects of some important parameters of the aquifer or pumping wells on drawdown and its derivative such as wellbore storage coefficient penetration ratio crossflow coefficient storativity ratio transmissivity ratio dimensionless aquifer thickness of anisotropy and skin factor are analyzed and discussed in detail

preliminary groundwater quality assessment in the central region of ghana insufficient knowledge of the hydrogeochemistry of aquifers in the central region of ghana has necessitated a preliminary water quality assessment in some parts of the region major and minor ions and trace metal compositions of groundwater have been studied with the aim of evaluating hydrogeochemical processes that are likely to impair the quality of water in the study area the results show that groundwater in the area is weakly acidic with mean acidity being 5 83 ph units the dominant cation in the area is na followed by k ca and mg and the dominant anion is cl followed by hco3 and so42 two major hydrochemical facies have been identified as na cl and na hco3 water types multivariate statistical techniques such as cluster analysis ca and factor analysis principal component analysis pca in r mode were employed to examine the chemical compositions of groundwater and to identify factors that influenced each q mode ca analysis resulted in two distinct water types as established by the hydrochemical facies cluster 1 waters contain predominantly na cl cluster 2 waters contain na hco3 and na cl cluster 2 waters are fresher and of good quality than cluster 1 factor analysis yielded five significant factors explaining 86 56 of the total variance pc1 explains 41 95 of the variance and is contributed by temperature electrical conductivity tds turbidity so42 cl na k ca mg and mn and influenced by geochemical processes such as weathering mineral dissolution cation exchange and oxidation reduction reactions pc2 explains 16 43 of the total variance and is characterized by high positive loadings of ph and hco3 this results from biogenic activities taking place to generate gaseous carbon dioxide that reacts with infiltrating water to generate hco3 which intend affect the ph pc3 explains 11 17 of the total variance and is negatively loaded on po43 and no3 indicating anthropogenic influence the r mode pca supported by r mode ca have revealed hydrogeochemical processes as the major sources of ions in the groundwater factor score plot revealed a possible flow direction from the northern sections of the study area marked by higher topography to the south compositional relations confirmed the predominant geochemical process responsible for the various ions in the groundwater as mineral dissolution and thus agree with the multivariate analysis

the origin of the tongkeng changpo tin deposit dachang metal district guangxi china clues from fluid inclusions and he isotope systematics tongkeng changpo is the largest tin deposit within the giant dachang polymetallic tin ore field in guangxi southern china which is part of a large skarn system associated with cretaceous granitoids the tongkeng changpo mineralization consists of veins and stockworks in the upper levels and replacement stratiform orebodies mantos at lower levels based on textural relationships three major mineralizing stages can be recognized stage i with cassiterite sulphides stannite tourmaline and quartz stage ii with cassiterite sulphides sulphosalts quartz and calcite and stage iii with calcite as the main phase the study of fluid inclusions has shown that there are two main fluid types co2 and nacl h2o homogenization temperatures are 270 to 365 c 210 to 240 c and 140 to 190 c for stages i ii and iii respectively salinities range from 1 to 7 wt nacl equiv in the early ore stage and 3 to 10 wt nacl equiv in the late stages laser raman spectroscopy indicates that the inclusion fluids in stages i and ii were of carbono aqueous composition with minor amounts of ch4 and h2s whereas those in stage iii were aqueous helium isotopic analyses of inclusion fluids indicate that the 3he 4he ratios in the ore veins are in between 1 2 to 2 9 ra ra 1 4 10 6 modern atmospheric ratio and range from 1 6 to 2 5 ra in the stratiform orebodies this range of 3he 4he ratios is significantly higher than that of crustal fluids 0 01 0 05 ra the similar characteristics of fluid inclusions and their he isotopic composition as well as age constraints indicate that the ore veins and stratiform orebodies of the tongkeng changpo deposit formed from the same hydrothermal system likely related to granite intrusions of the mesozoic yanshanian tectono thermal event in addition the high r ra ratios indicate a mantle contribution in the ore fluids

hydrogeochemistry of the sarada river basin visakhapatnam district andhra pradesh india systematic hydrogeochemical survey has been carried out for understanding the sources of dissolved ions in the groundwaters of the area occupied by sarada river basin visakhapatnam district andhra pradesh india khondalites charnockites and granite gneisses and calc granulites of precambrians and alluvial deposits of quaternaries underlie the study area groundwaters are both fresh and brackish the latter waters being a dominant most groundwaters are characterized by na hco 3 facies due to chemical weathering of the rocks enrichment of na k cl so 4 2 no 3 and f in some groundwater samples is caused by seawater intrusion locally accompanied by ion exchange and anthropogenic activities resulting in an increase of brackish in the groundwaters based on the results of this hydrogeochemical study suitable management measures are recommended to solve the water quality problems

groundwater flow to a general well configuration in an unconfined aquifer overlying a fractured bedrock abstract unconfined aquifers sometimes overlie fractured bedrocks consisting of unconfined fractured aquifer systems pumping induced hydrodynamics in such aquifer systems has not received much attention as in other types of aquifer systems this paper aims to obtain semi analytical solutions of flow to a general well configuration in such an unconfined fractured two layer aquifer system the examples of general well configuration specifically discussed here include 1 a horizontal well 2 a vertical well 3 a vertical well with one horizontal collector and 4 a vertical well with two horizontal collectors which are perpendicular with each other the methodology is general and can be extended to other types of wells with minor modifications of solutions developed in this study the point sink source solution is first obtained using double infinite fourier and laplace transformations where sink is for pumping and source is for injection the line sink source solution is then obtained via integrating the point sink source along the desired direction and following the principle of superposition the de hoog numerical inverse laplace transform and gaussian quadrature are used to obtain time domain dimensionless drawdown solutions the instantaneous drainage of water table and the inter porosity flow of the underlying fractured aquifer are taken into account the effects of the length of horizontal well on dimensionless drawdown and dimensionless drawdown derivative and scaled sensitivity of the hydraulic parameters of the underlying fractured aquifer are explored the dimensionless drawdowns and drawdown derivatives of a vertical pumping well a vertical well with a single horizontal collector and a vertical well with two perpendicular horizontal collectors are also compared the scaled sensitivity of dimensionless drawdown to the hydraulic parameters of the underlying fractured aquifer of these different pumping well structures is explored the results of this study can be used to evaluate the hydraulic parameters using the drawdown data collected during a pumping test performed in a general well configuration in a unconfined fractured two layer aquifer system furthermore the presented solutions can be utilized to design the pumping well to minimize drawdown in low permeability or thin aquifers by eliminating the inter porosity flow term from the underlying fractured aquifer the solutions are applicable to groundwater flow to a pumping well in leaky aquifers

new aspects on the formation of hydrocarbon source rocks episodic volcanism favors as shown by examples from europe the usa and brazil the formation of organic rich sediments hydrocarbon source rocks the examples examined from europe comprise the lower carboniferous oil shale group scotland upper carboniferous coal measures western germany upper jurassic kimmeridge shale north sea area lower cretaceous blattertonstein northwest germany and eocene messel oil shale rheingraben examples from the usa are devonian mississippian gas shales permian phosphoria shale middle cretaceous mowry shale eocene green river shale and miocene monterey shale examples from brazil are permian irati oil shale and oligocene paraiba valley oil shale volcanism is reflected during sedimentation 1 by exhalation of so2 and or co2 2 volcanic ashfalls 3 by generation of anoxia and preservation of organic matter and 4 by halmyrolytic alteration of volcanic ashes into highly surface active clay minerals montmorillonite

reassessment of proterozoic granitoid ages in ghana on the basis of u pb zircon and monazite dating abstract the west african craton in ghana is of early proterozoic age and forms alternating volcanic belts and sedimentary basins made up of rocks of the birimian supergroup as well as younger conglomerates and quartzites of the tarkwaian group and extensive granitoid plutons no consensus exists on absolute and relative ages of plutons within belts and basins u pb geochronology of four different granitoid complexes indicates that contrary to long held views belt granitoid plutons ashanti belt 2172 2 ma sefwi belt 2179 2 ma are 60 to 90 ma older than basin plutons kumasi basin 2116 1 ma belt granitoid are approximately coeval with volcanic rocks of the birimian supergroup while basin plutons are late kinematic and postdate tarkwaian sedimentation the first high precision geochronological data for rocks from ghana i e the eastern part of the birimian domain on the west african craton presented here show that magmatism within this region occurred over a time span of at least 90 ma and provide further evidence that the period between 2 1 and 2 2 ga was one of important magmatism in west africa

genesis of the jianzhupo sb pb zn ag deposit and formation of an ore shoot in the wuxu ore field guangxi south china abstract the jianzhupo sb pb zn ag deposit in the southeastern dachang sn polymetallic ore belt guangxi region south china is the largest deposit in the wuxu district and is hosted by devonian limestone and mudstone the deposit mainly comprises a stage i jamesonite sphalerite ore shoot and stage ii jamesonite sphalerite calcite quartz jscq veins we use homogenization temperatures salinities and the h o isotopic compositions of fluid inclusions from the jianzhupo deposit to constrain the genesis of the deposit and determine factors that controlled the formation of the ore shoot fluid inclusions from both stages of mineralization contain large volumes of co2 and minor bitumen c6h6 and ch4 fluid inclusions from the ore shoot yield homogenization temperatures of 120 c 290 c mainly 250 c 270 c and salinities of 3 4 13 6 wt nacl equiv fluid inclusions from the stage ii mineralization yield homogenization temperatures of 150 c 350 c mainly 240 c 310 c and salinities of 1 4 12 0 wt nacl equiv ore forming fluids of the jianzhupo deposit yield 18oh2o and dv smow values of 4 9 9 9 and 78 to 111 respectively and plot close to the composition of magmatic water on the dv smow vs 18oh2o diagram co2 in the ore forming fluids was likely generated through deep skarnization beneath the wuxu ore field rather than from metamorphism thermal degradation or the oxidization of organic matter h o isotopic compositions of ore forming fluids that contain large volumes of co2 with minor bitumen and c6h6 indicate that they were derived from magmatic water that was mixed with basin brines ore forming fluids of the stage i ore shoot yield lower 18oh2o values 4 9 6 7 than those associated with the stage ii mineralization 7 5 9 9 moreover ore forming fluids of the ore shoot and the jscq veins yield strongly and weakly positive correlations between homogenization temperature and salinity respectively this difference suggests that rapid and large scale mixing between magmatic water and basin brines was the key factor that controlled the formation of the ore shoot

early proterozoic ore deposits and tectonics of the birimian orogenic belt west africa abstract the early proterozoic of the west african craton comprises a series of volcanic troughs and sedimentary basins the birimian with granitic terranes accreted on archean nuclei in the man and reguibat shields studies of the birimian of the man shield indicate a model of polycyclic evolution with a major collision event d 1 2 1 ga thrusting part of the proterozoic terrane over the archean before individualization of numerous volcanic troughs and clastic infill basins the proposed evolution for the birimian orogenic belt comprises 1 deposition of the sedimentary lower birimian b1 with minor tholeiitic volcano sedimentary intercalations containing chert and or mn formations and with most of the detritus being derived from early proterozoic sources apart from contamination near the proterozoic archean contact 2 pre b2 crustal thickening related to d 1 thrusting 3 formation over about 40 ma of the upper birimian b2 with numerous volcanic troughs of different composition tholeiitic and rare komatiitic bimodal tholeiitic to calc alkaline volcano plutonic and tarkwaian clastic infill basins and 4 major transcurrent tectonics with sinistral d 2 and dextral d 3 strike slip faults such a tectonic evolution from a collision d 1 phase to a transcurrent d 2 d 3 phase is typical of collision belts and in the present case the evolution of the birimian orogenic belt can be extended into guyana the metallogenic history of the birimian shows a three phase evolution coinciding with the orogenic evolution and extends over almost 150 ma from the perkoa massive zn ag sulfides 2 12 ga with a clear mantle affinity to the latemesothermal au quartz veins 2 ga with according to lead isotopes a high crustal participation the economic mineralization of belt thus consists of 1 1 pre orogenic pre d 1 deposits related to early extension zones this was diverse with stratiform au tourmalinite type 1 au loulo in mali dorlin in guyana stratiform fe cu faleme in senegal and mn nsuta in ghana tambao in burkina faso and a single massive zn ag sulfide deposit perkoa in burkina faso associated with regional volcanosedimentary variably tholeiitic stratigraphic marker beds 2 2 syn orogenic post d 1 to syn d 2 d 3 deposits with disseminated au sulfides type 2 au yaoure in the ivory coast in extensional zones of the b2 followed by auriferous paleoplacers type 3 au in b2 extensional zones tarkwaian banket conglomerate or syn d 2 transtensional zones debris flow of orapu in guyana 3 3 late orogenic post peak d 2 d 3 deposits with mesothermal au mineralization evolving from a disseminated gold bearing arsenopyrite and au quartz lode type type 4 au ashanti in ghana to a quartz vein type with free gold and cu pb zn ag bi paragenesis most of the gold in west africa comes from this phase finally the metallogeny of the birimian appears as rich in au and mn formations and poor in volcanogenic mineralization and bif it differs from the archean metallogeny of west africa and other regions through the presence of certain deposit types such as au stratiform tourmalinite gold bearing conglomerate with au and fe ti oxides but no uranium or sulfides and au arsenopyrite rich shear zone deposits that are very common in but not exclusive to the proterozoic and paleozoic

semi analytical solution for flow in leaky unconfined aquifer aquitard systems this study presents a semi analytical solution for the problem of leakage in an unconfined aquifer bounded below by an aquitard of finite or semi infinite extent the homogeneous anisotropic unconfined aquifer of infinite radial extent is pumped continuously at a constant rate from a well of infinitesimal radius the aquitard is also homogeneous anisotropic and of infinite radial extent flow in both the aquifer and the aquitard is allowed to occur both vertically and horizontally exact solutions to the governing equations given in this work are developed in the double laplace hankel transform space for drawdown response in the unconfined aquifer and the underlying aquitard the inverse transforms of the solutions are obtained numerically the theoretical results show that leakage can cause significant departure at both early and late times from the solution with no leakage the solution presented here can be used in least squares routines for estimation of hydraulic parameters for two layered unconfined aquifer aquitard systems

constant head test at a partially penetrating well in an aquifer aquitard system abstract an analytical model for describing pumping induced drawdown by constant head test at a partially penetrating well in a leaky confined aquifer is developed by treating the leakage of aquitard storage as an interface phenomenon rather than an volumetric effect which is the novel and never developed so far three different cases of remote lateral boundaries are considered in the model the new drawdown solution in laplace space is obtained and inverted into time domain solution utilizing the stehfest method the semi analytical solutions for well discharge are then obtained under three different cases analytical solutions in laplace and time domains are developed for calculating the total leakage rate and volume across the aquitard aquifer interface due to constant head test at a partially penetrating well in a leaky confined aquifer and such solutions are of great use for groundwater resource management based on the newly developed solutions the distribution of wellbore flowrate and aquitard leakage are explored and the sensitivity analysis is conducted to identify the most important controlling factor the sensitivity analysis shows that the wellbore flowrate and the drawdown in infinite case 1 finite case 2 and closed case 3 leaky confined aquifer systems are both sensitive to the variation of well partial penetration well radius and aquifer anisotropic ratio during the whole pumping period and they are most sensitive to the change of outer boundary distance at late time for case 3 the effect of the outer boundary on the drawdown or wellbore flowrate is more significant for a shorter outer boundary distance

40ar 39ar thermochronology of paleoproterozoic granitoids of northeast burkina faso west african craton implications for regional tectonics abstract the greenstone belts of northeast burkina faso in the west african craton wac comprise birimian meta sedimentary and mafic ultramafic complexes that are intruded by granitoids and late dolerite dykes the granitoid greenstone belt assemblages underwent at least two phases of deformation that have resulted in their principal nw and ne trends we performed a detailed 40ar 39ar dating together with zircon u pb ages in order to unravel the thermo chronological history of the studied granitoids our previous zircon u pb data indicated that the granitoids were emplaced between 2138 7 and 2181 7 ma this period is well known for crustal growth in the wac the emplacement of granitoids was concomitant with d1 or the tangaean event 2130 2170 ma amphibole and micas yield two 40ar 39ar age groups the first group 2046 12 2132 13 ma constrained the d2 deformation event and the second group 1918 24 to 1984 12 ma constrained the d3 or wabo tempelse event considering closure temperatures of the isotopic systems the u pb ages and the present 40ar 39ar dating results suggest that after emplacement the granitoids cooled to 315 c at ca 2020 ma with a mean cooling rate of 6 5 c ma corresponding to a mean uplift rate of 0 65 km ma the additional k feldspar 40ar 39ar data indicate a later slow cooling stage with a rate of 0 54 c ma corresponding to a mean uplift rate of 0 054 km ma subsequent to the end of the major crustal growth in the wac at 2000 ma

flow to a well in an unconfined fractured and leaky wedge shaped aquifer system abstract wedge shaped aquifers are usually formed where two linear boundaries intersect these types of aquifers are commonly seen in river basins and alluvial fans but have received much less attention in the hydrological sciences community fundamental understanding of the effects of lateral boundaries on the hydrodynamic process in such aquifers is quite poor particularly for unconfined fractured and leaky wedge shaped aquifer systems which will be the concern of this study solutions of flow to a well in an unconfined fractured wedge shaped two aquifer system are obtained using laplace hankel and fourier transforms an infinitesimal radius pumping well partially penetrates the overlying unconfined aquifer both aquifer layers are homogeneous and anisotropic bounded by two intersecting linear lateral boundaries of constant head or barrier types and the aquifer system is semi infinite in radial direction the time domain drawdowns are obtained via the stehfest algorithm and gaussian quadrature the inter porosity flow in the underlying fracture aquifer the instantaneous water table drainage the horizontal and vertical hydraulic conductivity anisotropy and the wedge angle are taken into account eliminating the inter porosity flow in the underlying fractured aquifer the presented solution reduces to a leaky wedge shaped aquifer case the influences of the underlying fractured aquifer hydraulic parameters on the overlying unconfined aquifer for different wedge angles and linear lateral boundaries types are explored using dimensionless drawdown and scaled sensitivity curves the results of this study can be utilized to obtain hydraulic parameters of an alluvial and river basin unconfined fractured wedge shaped aquifer systems the presented solution can also be used for water budget assessment of river basin aquifers

genesis of tin dominant polymetallic deposits in the dachang district south china insights from cassiterite u pb ages and trace element compositions abstract the dachang tin dominant polymetallic district in western south china hosts a total reserve of 110 mt ore 1 sn 3 5 by products of zn pb sb in and cu and 100 to 300 g t ag economic tin orebodies in the district mainly developed in devonian limestone black shale and siliceous rocks as massive stratiform and vein stockwork mineralization la icp ms u pb dating on seven cassiterite samples from the tongkeng changpo and gaofeng sn zn pb deposits and the dafulou huile and kangma sn zn deposits yields weighted mean 206pb 238u ages ranging from 90 3 1 8 ma to 95 4 4 9 ma these dates are significantly younger than the devonian ore hosted strata but agree well with the previously published zircon u pb ages of 96 6 93 9 ma for the longxianggai biotite granite within analytical uncertainties showing a close temporal link between the granitic magmatism and tin mineralization cassiterite grains from various ore types in the dachang district show clear growth zonations as reflected from their cathodoluminescence images la icp ms trace element analyses of cassiterite grains indicate that they have relatively high ti fe and w but low nb and ta contents which corresponds to the clear luminescencing chemical variations of cassiterite from different ore types i e cassiterite sulfide ores and cassiterite bearing quartz veins are indistinguishable except for more enriched fe in cassiterite from cassiterite quartz veins combined with cretaceous u pb ages elevated fe and w contents of cassiterite suggest tin dominant polymetallic deposits in the dachang district were formed in a granite related magmatic hydrothermal system controlled by the longxianggai biotite granite precluding their syngenetic origin

evolution of the precambrian in ouzzal block central sahara algeria abstract new structural and geochronological data are used to constrain the evolution of the precambrian in ouzzal block situated on the eastern side of the west african craton the results of this study can be summarized as follows 1 i the block can be subdivided into two series one is mainly composed of archaean granitic gneisses 3 2 2 5 ga old while the other contains metasedimentary and basic to ultrabasic rocks which can be compared with those described in archaean supracrustal terrains 2 ii the entire block is affected by very high temperature granulite facies metamorphism 3 iii the metamorphism is associated with two main deformational phases the first of which is responsible for a regional foliation foliation refolded during the second phase 4 iv the major tectono metamorphic event in the area is related to a 2 0 ga old eburnian orogeny which ended with carbonatite emplacement nearly all evidence of the earliest crustal evolution events i e the initial emplacement and deformation of the granitic and supracrustal materials has been erased by the eburnian event

a method of calculating pumping induced leakage summary we have discussed pumping induced leakage in a leaky confined aquifer bounded by a relatively thin aquitard whose storage effect is neglected both constant rate and constant drawdown fully penetrating vertical pumping wells are considered we have derived closed form analytical solutions of the steady state leakage rates and volumes within any given radial distance from the well for both the constant rate and constant drawdown pumping wells for the constant rate well we have derived the closed form analytical solutions for the total leakage rate and volume over the entire aquitard aquifer boundary at a given time and the semi analytical solutions for calculating the leakage rate and volume within any radial distance from the pumping well at a given time for the constant drawdown well we have further provided the analytical solutions of the leakage rate and volume in the laplace domain those solutions are numerically inverted to yield results in the real time domain with the scale invariant relationship of butler jr j j tsou m s 2003 pumping induced leakage in a bounded aquifer an example of a scale invariant phenomenon water resour res 39 12 1344 doi 10 1029 2002wr001484 the solutions of the total leakage rates and volumes can be generalized to finite size aquifers with lateral impermeable boundaries these solutions are useful for managing multi layer aquifers in which pumping induced water transfer across the aquitards can occur

neoproterozoic mineralization in a hydrothermal cassiterite sulfide deposit at jiumao northern guangxi south china mineral scale constraints on metal origins and ore forming processes abstract most tin deposits worldwide are inferred to have formed from fluids derived from evolved granitic magma systems neoproterozoic silicate and sulfide stage sn deposits at jiumao of south china in contrast have been thought to be derived from metasedimentary and mafic ultramafic host rocks the sn deposit may thus have formed by components and processes distinct from those that commonly contribute to sn deposits although spatially associated greisen hosted sn deposits also occur to characterize in detail the formation of the jiumao ore deposits which contain 28 000 t of sn we present new field and petrographic observations major and trace element compositions for silicate and ore minerals and u pb age data of cassiterites and zircons for the deposits and granites our research shows that 1 the granite greisen system formed at 830 ma which is the earliest sn mineralization event in south china 2 the silicate and sulfide stage ores in the country rocks formed at an fo2 of nno with temperatures of 350 c and 170 c respectively 3 all vein type sn ores at jiumao were formed by sn f b rich fluids that were derived from the yuanbaoshan granite magma system rather than ultramafic rocks 4 the fe rich character of the ores hosted by the metasedimentary rocks and the mg rich character of the ores hosted by the ultramafic rocks largely controlled the reactions and efficacy of cassiterite precipitation and thus ore grade we highlight that differences in mineral assemblages largely relate to differences of the protolith compositions and fluid rock reactions e g b and tourmaline deposition in the ores hosted by the metasedimentary rocks but not in the ores hosted by the ultramafic rocks cassiterite and titanite trace element compositions reflect fluid composition protolith composition and intensive parameters of crystallization

three dimensional saturated unsaturated flow with axial symmetry to a partially penetrating well in a compressible unconfined aquifer 1 a new analytical solution is presented for the delayed response process characterizing flow to a partially penetrating well in an unconfined aquifer the new solution generalizes that of neuman 1972 1974 by accounting for unsaturated flow above the water table three dimensional axially symmetric flow in the unsaturated zone is described by a linearized version of richards equation in which hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value defining the interface between the saturated and unsaturated zones unsaturated soil properties are characterized by an exponent having the dimension of inverse length or equivalently a dimensionless exponent d b where b is initial saturated thickness our treatment of the unsaturated zone is similar to that of kroszynski and dagan 1975 who however have ignored internal artesian aquifer storage according to kroszynski and dagan aquifers that are not excessively shallow have values of d their parameter a much greater than 10 we find that in such typical cases unsaturated flow has little impact on early and late dimensionless time drawdown a short distance below the water table unsaturated flow causes drawdown to increase slightly at intermediate dimensionless time values that represent transition from an early artesian dominated to a late water table dominated flow regime delayed drainage from the unsaturated zone becomes less and less important as d increases as d this effect dies out and drawdown is controlled entirely by delayed decline in the water table as in the model of neuman the unsaturated zone has a major impact on drawdown at intermediate time and a significant impact at early and late times in the atypical case of d 1 becoming the dominant factor as d approaches zero the soil water retention capacity becomes very large and or saturated thickness becomes insignificant our new solution was used to analyze field data from a pumping test conducted by moench et al 2001 in a glacial outwash deposit at cape cod massachusetts the solution was fitted individually and simultaneously to time drawdown data from 20 piezometers and observation wells and simultaneously to data from three piezometers in each of two clusters at various depths and distances from the pumping well with very good results our parameter estimates of hydraulic conductivities from the simultaneous fit are similar to those obtained previously by moench 2004 but our estimates of specific yield and storage are smaller and larger respectively while our estimate of is not comparable with his estimates of three empirical parameters

sulfur isotope distribution and contamination related to the balya pb zn mine in turkey sulfur isotope 34s values and weight of acid volatile sulfur avs chrome reducible sulfide crs elemental sulfur es and acid soluble sulfates were determined in balya mine ore rock mine wastes and kocacay river and lake manyas sediments estimation of isotopic fractionation 34s between product sulfate and initial crs pyrite was used to evaluate the progress of sulfide oxidation in the mine waste area water and acid soluble sulfate produced from different mine waste samples such as metallurgical waste mw and waste rock wr in laboratory experiments also shows distinct 34s values and allows identification of the acid mine drainage sources in the mine waste area average 34sso4values are 1 43 for mw n 4 and 2 06 for wr n 8 short 24 hr and long 60 days term leach experiments were considered using alternating wet dry conditions to simulate sulfate production capacity and metal discharge characteristics for mw and wr piles release of heavy metals follows the order of pb2 mn2 zn2 cu2 for these pile samples values of 34sso4 for river water that was collected after 3 4 h of heavy rainfall are close to values of 34sso4 for water soluble sulfates from mine waste piles used in laboratory leach experiments

an oxygen hydrogen sulfur and carbon isotope study of carbonate replacement skarn tin deposits of the dachang tin field china the dachang tin field located in guangxi province of southern china is one of the largest in the world it comprises the changpo bali and longtaoshan carbonate replacement tin deposits and the lamo cu zn skarn deposit these deposits are hosted by devonian carbonate rich sedimentary rocks which have been metamorphosed to calc silicate skarn and marble near the contact of the longxianggei granite calculated delta 18 o sub h 2 o values of the hydrothermal fluids in equilibrium with quartz cassiterite and calcite are 10 6 and 11 6 9 1 to 10 2 and 7 5 to 9 8 per mil respectively measured delta d values of fluid inclusion waters in cassiterite and calcite are 115 and 120 and 73 to 93 per mil respectively the decrease in the calculated delta 18 o sub h 2 o values from 11 6 to 7 5 per mil is attributed to increase in the co 2 content of the hydrothermal fluids the low delta d values of fluid inclusion waters in cassiterite may be the result of decreasing ch 4 co 2 as the originally magmatic fluid migrated from reducing conditions in carbonaceous black shale to oxidizing conditions in pure limestone oxygen and hydrogen isotope data indicate that the hydrothermal fluid was derived from the longxianggei granite variations in delta 13 c and delta 18 o values of calcite in orebodies altered limestone and marble are due to continuous isotopic exchange reaction between magmatic fluid and carbonate rocks at variable water to rock ratios between 300 degrees to 600 degrees c sulfur isotope data indicate that host rocks controlled the variations in sulfur isotope compositions of sulfide minerals in different deposits of the tin field with significant contribution of sulfur from magmatic fluids

the empire cu zn mine idaho exploration implications of unusual skarn features related to high fluorine activity the empire cu zn skarn deposit is unusual because of the proximal position of zn mineralization abundance of endoskarn and the extremely vermicular texture of quartz phenocrysts in the related intrusive rocks cu zn skarn occurs at the contact between upper mississippian white knob limestone and the granite porphyry phase of the mackay stock which consists from early to late of quartz monzodiorite granophyre granite porphyry porphyritic granite and many dikes the late phases have high f and also extremely vermicular quartz phenocrysts endoskarn is more abundant than exoskarn the earliest alteration of the intrusive rocks consists of disseminated diopsidic pyroxene di64hd36 to di88hd12 actinolite and titanite this assemblage was cut by early scapolite me18 to me35 mostly me18 26 and or green pyroxene di14hd80 to di20hd77 veinlets with or without wollastonite halos these early veins were then cut by main stage endoskarn veins that typically have a garnet minor pyroxene inner zone a wollastonite and or pyroxene ca rich plagioclase an56 to an89 envelope and a halo containing disseminated fine grained alteration minerals of the same assemblage as the envelope some veins contain only the envelope assemblage and are interpreted to represent the alteration front the inner zone locally contains vesuvianite where many veins intersect endoskarn is massive pyroxene is zoned around fluid conduits the distal pyroxene is fe rich hedenbergitic whereas the proximal pyroxene is fe poor diopsidic the garnet changes in the opposite way being fe poor al rich grossularitic in locations distal to the fluid conduits and fe rich andraditic in proximal locations in contrast in the exoskarn all pyroxene is diopsidic and garnet is andraditic weak retrograde alteration composed of quartz calcite chlorite with minor fluorite talc and epidote overprinted both endoskarn and exoskarn magnetite precipitated after garnet pyroxene in both endoskarn and exoskarn sphalerite precipitated together with chalcopyrite in proximal locations and is associated with retrograde alteration other ore minerals include minor molybdenite bornite pyrite galena arsenopyrite native au as well as supergene minerals such as chrysocolla malachite azurite native cu and limonite fluid xenoliths from pyroxene in early endoskarn veinlets homogenize at 600 c massive endoskarn and exoskarn replacing limestone inclusions in granite porphyry formed at 500 to 700 c whereas the highest temperature inclusions 700 c occur in narrow garnet minor pyroxene veins fluid inclusions in exoskarn replacing wall rock have homogenization temperatures of 500 to 650 c retrograde alteration and cu zn mineralization occurred at 250 to 300 c fluid inclusions in prograde minerals contain daughter minerals whereas fluid inclusions in retrograde minerals do not indicating a decrease in salinity with time late stage fluids have low eutectic temperatures indicating the possible presence of kcl nacl fecl2 cacl2 mgcl2 k2co3 and or na2co3 formation of the unusually abundant endoskarn the proximal position of zn mineralization and the extremely vermicular texture of quartz phenocrysts are all believed to have been promoted by the high f content of the magmatic fluid these features may serve as exploration indicators of associated high f mineralization such as buried porphyry mo deposits

aquitard effect on drawdown in water table aquifers 1 the effects of an aquitard on drawdown in an overlying unconfined aquifer can be represented by a drainage type term at the aquitard aquifer interface the functional form of this boundary condition is similar to the boulton neuman boundary condition used for water table aquifers except the kernel contains an inverse square root of time instead of a negative exponential type curves using the new boundary condition were obtained in semianalytical form examples for several representative conditions show that the effect of the underlying aquitard can contribute to the type curve at early and intermediate times but the effect becomes negligible at late times

early proterozoic crustal evolution in the birimian of ghana constraints from geochronology and isotope geochemistry abstract representative suites of ghanaian granitoids metavolcanics and metasediments were selected from birimian rock units for rb sr pb pb and sm nd analyses isotopic data on the igneous rocks provide evidence for a major early proterozoic crust forming episode which took place over a maximum time interval from 2 3 to 2 0 ga by a differention from a depleted mantle source there is little evidence for the involvement of significantly older e g archaean crust in the genesis of the igneous rock units the only exception so far found is the winneba granitoid which appears to contain a magmatic contribution from presumably underlying archaean basement sm nd model ages indicates that birimian sediments were derived from adjacent penecontemporaneous volcanic belts the birimian of ghana forms part of a major proterozoic eburnean episode of juvenile crustal accretion which has been recognised in the surrounding areas of mauretania senegal ivory coast burkina faso mali and niger where it has been dated at 2 1 2 2 ga abouchami et al the birimian terranes bridge a major gap in mantle activity and associated crustal evolution for a period considered as quiescent on other continents

flow to a partially penetrating well with variable discharge in an anisotropic two layer aquifer system abstract a general analytical model for the problem of variable discharge of groundwater from a well in an anisotropic two layered aquifer system is developed by taking account of the interface flow between the two layers the well of infinitesimal radius partially penetrates the lower layer and is pumped at a variable discharge the horizontal as well as vertical flows in both layers are included and importantly the effects of constant head case 1 and no flux case 2 boundaries at the top of the upper layer are considered laplace domain solutions for drawdown in dimensionless form are derived with the help of hankel transform and are inverted to the time domain numerically the drawdown characteristics induced by an exponentially decayed rate of pumping are discussed and sensitivity analysis is also performed to explore the influence of different parameters on drawdown characteristics the results show that the drawdown around a partially penetrating well in the lower pumped layer induced by an exponential decreasing pumping rate usually contains three stages the effect of anisotropy and well configuration have great influences on the drawdown distribution near the pumping well and the horizontal flow and storativity of the upper unpumped layer cannot be ignored in determining the upper aquifer drawdown the sensitivity analysis also illustrates that the dimensionless drawdown in the lower pumped layer is very sensitive to well configuration parameters all the time it is only sensitive to the hydraulic parameters of the lower aquifer for case 1 and to the hydraulic parameters of the lower layer and the specific storage of the upper layer at late times the dimensionless drawdown of the upper layer is not sensitive to the variable well discharge parameters over the whole pumping period and is not sensitive to the storage parameters of both layers for case 1 however the drawdown in the upper layer is sensitive to all the hydraulic parameters and well configuration parameters for case 2 at late times

three dimensional response to a partially penetration well pumping in a general anisotropic three layer aquifer system abstract three dimensional response to well pumping in a multilayer aquifer system with rigorous treatment of interfacial flow attracts great attention among the subsurface hydrologists because of its theoretical importance and practical merits in this study a general theory of three dimensional groundwater flow to a well of infinitesimal radius in an anisotropic three layer aquifer system is developed with a constant rate pumping in the lower layer and associated semi analytical solutions of drawdowns in individual layers are obtained this theory discards many previous assumptions for studying a multilayer aquifer system such as simplified flow configuration in the aquitard treatment of cross formation flow as a volumetric averaged term adding to the governing equations of aquifer flows and sometimes negligence of vertical flow components in the aquifers additionally this theory considers three types of commonly used top boundary conditions a water table with delayed gravity drainage boundary condition case 1 a constant head top boundary condition case 2 and a no flow top boundary condition case 3 the dimensionless drawdown solutions in laplace domain are obtained and inverted numerically to calculate the time domain solutions the solution encompasses existing solutions for a two layer or a single layer e g unconfined or confined aquifer system as subsets the developed solutions are tested extensively with a finite element numerical solution using comsol and other existing solutions and a sensitivity analysis is performed to prioritize the influences of different parameter groups the results of this study can be used to predict the pumping induced drawdown at any position with an observation well and to estimate the hydraulic parameters of the lower pumped layer and upper layer as well as the middle layer the developed theory provides a basis for other potential applications such as geotechnical engineering and groundwater management