differentiation and crystallization conditions of basalts from the kerguelen large igneous province an experimental study phase relations of basalts from the kerguelen large igneous province have been investigated experimentally to understand the effect of temperature fo2 and fugacity of volatiles e g h2o and co2 on the differentiation path of lip basalts the starting rock samples were a tholeiitic basalt from the northern kerguelen plateau odp leg 183 site 1140 and mildly alkalic basalt evolved from the kerguelen archipelago mt crozier on the courbet peninsula representing different differentiation stages of basalts related to the kerguelen mantle plume the influence of temperature water and oxygen fugacity on phase stability and composition was investigated at 500 mpa and all experiments were fluid saturated crystallization experiments were performed at temperatures between 900 and 1 160 c under oxidizing log fo2 qfm 4 and reducing conditions log fo2 qfm in an internally heated gas pressure vessel equipped with a rapid quench device and a pt membrane for monitoring the fh2 in all experiments a significant influence of the fo2 on the composition and stability of the mg fe bearing mineral phases could be observed under reducing conditions the residual melts follow a tholeiitic differentiation trend in contrast melts have high mg mg2 mg2 fe2 and follow a calk alkalic differentiation trend at oxidizing conditions the comparison of the natural phenocryst assemblages with the experimental products allows us to constrain the differentiation and pre eruptive conditions of these magmas the pre eruptive temperature of the alkalic basalt was about 950 1 050 c the water content of the melt was below 2 5 wt h2o and strongly oxidizing conditions log fo2 qfm 2 were prevailing in the magma chamber prior to eruption the temperature of the tholeiitic melt was above 1 060 c with a water content below 2 wt h2o and a log fo2 qfm 1 early fractionation of clinopyroxene is a crucial step resulting in the generation of silica poor and alkali rich residual melts e g alkali basalt the enrichment of alkalis in residual melts is enhanced at high fo2 and low ah2o

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

on the skaergaard intrusion and forward modeling of its liquid line of descent a reply to principles of applied experimental igneous petrology by morse 2008 lithos 105 pp 395 399 abstract forward modeling based on an experimental investigation successfully duplicated main features of the gabbros in the skaergaard layered series thy p lesher c e nielsen t f d and brooks c k 2006 experimental constraints on the skaergaard liquid line of descent lithos 92 154 180 the foundation for the modeling was equilibrium melting experiments that were controlled by temperature and oxygen fugacity at low pressure conditions the experimental techniques and methods were chosen to represent a reasonable approximation to the inferred emplacement and crystallization conditions of the skaergaard intrusion the dike rocks used as starting materials define a strong differentiation trend that represents the skaergaard liquid line of descent this suite of dikes allowed liquidus conditions to be defined for a range of composition and temperature the initial redox conditions were chosen based on measured and calculated estimates for the gabbros of interest the melting experiments defined liquidus and subliquidus conditions that were used to understand crystallization of the lower and middle zones of the skaergaard layered series and can be extrapolated to the upper zone gabbros assuming perfect fractional crystallization the forward modeling reproduces the cryptic variation seen in the main gabbro minerals olivine augite plagioclase well into the upper zone and provides reasonable liquidus temperatures and compositions it can be shown that based on the assumption of fe ti oxide modes in the middle and upper zones a range of oxygen fugacity trends can be obtained we repeat our previous conclusion that iron depletion and strong reduction in oxygen fugacity in the upper zone are only feasible for very high fe ti oxide modes that exceed the experimental evidence as well as the observations from the gabbros a strong drop in oxygen fugacity in the upper zone requires a significant sink for fe ti oxides that so far has not been identified we thus reject morse s morse s a 2008 principles of applied experimental igneous petrology a comment on experimental constraints on the skaergaard liquid line of descent by thy lesher nielsen and brooks 2006 lithos 92 154 180 lithos 105 pp 395 399 contention that we violated in our original study established principles of applied experimental igneous petrology such principles dictate that experimental and forward models are carefully tested against field observations before petrologic processes can be verified

a 1 78 ga large igneous province in the north china craton the xiong er volcanic province and the north china dyke swarm abstract the 1 78 ga xiong er volcanic province xvp and coeval north china giant mafic dyke swarm ncds are the most important magmatic events occurring after the amalgamation of the north china craton ncc the xvp consists of 3 7 km of extrusive volcanics and some feeder dykes sills located along the southern margin of the ncc and extending over an area 0 06 m km2 compositions vary from basalt to rhyolite but are predominantly intermediate in terms of silica content there are also minor sedimentary intercalations and pyroclastic units the sedimentary interlayers indicate an environment changing from continental facies to oceanic facies up section the xvp is characterized by fractional crystallization from an em i type mantle source and both continental arc andean type and rift environments have been proposed the ncds is widespread in the central ncc with an outcrop area 0 1 m km2 and are exposed at variable depths up to 20 km deepest in the north dyke compositions vary from basalt to andesite and dacite but are dominantly mafic and comprise two series of magmatism previous studies revealed that the ncds recorded assimilation and fractional crystallization of an em i type magma source with a minor dm contribution in the younger magmas both syn collisional and intra continental anorogenic environments have been proposed spatial and petrogenic correlations suggest a cogenetic relationship between the ncds and xvp and considered together they define a large igneous province lip of 0 1 m km2 in area and 0 1 m km3 in volume which is also notable for its continuous compositional range from mafic to felsic with no gap at intermediate compositions the petrology is explained by a common magma source that undergoes a silica poor and iron enriched fractionation trend at depth followed by a silica rich and iron poor fractionation trend in shallow level magma conduits dykes and surface lavas a mantle plume is favored as the cause of this 1 78 ga north china lip

performance of fractured horizontal well with stimulated reservoir volume in unconventional gas reservoir summary this paper extended the conventional multiple hydraulic fractured horizontal mfh well into a composite model to describe the stimulated reservoir volume srv caused by hydraulic fracturing employing the laplace transform source function and dirac delta function methods the continuous linear source function for general composite dual porosity is derived and the solution of the mfh well in a composite gas reservoir is obtained with the numerical discrete method through the stehfest numerical algorithm and gauss elimination method the transient pressure responses for well producing at a constant production rate and the production rate vs time for constant bottomhole pressure are analyzed the effects of related parameters such as natural permeability and radial of the srv region formation permeability and interporosity coefficient on transient pressure and production performance are analyzed as well the presented model and obtained results in this paper not only enrich the well testing models of such unconventional reservoir but also can use to interpret on site data which have significance on efficient reservoir development

liquid immiscibility and the evolution of basaltic magma this experimental study examines relationships between alternative evolution paths of basaltic liquids the so called bowen and fenner trends and silicate liquid immiscibility synthetic analogues of natural immiscible systems exhibited in volcanic glasses and melt inclusions were used as starting mixtures conventional quench experiments in 1atm gas mixing furnaces proved unable to reproduce unmixing of ferrobasaltic melts yielding instead either turbid opalescent glasses or crystallization of tridymite and pyroxenes in contrast experiments involving in situ high temperature centrifugation at 1000g g 1 4 9 8 m s did yield macroscopic unmixing and phase separation centrifugation for 3 4 h was insufficient to complete phase segregation and resulted in sub micron immiscible emulsions in quenched glasses for a model liquid composition of the middle zone of the skaergaard intrusion at super liquidus temperatures of 1110 11208c centrifugation produced a thin silicic layer 64 5 wt sio2 and 7 4 wt feo at the top of the main fe rich glass 46 wt sio2 and 21 wt feo the divergent compositions at the top and bottom were shown in a series of static runs to crystallize very similar crystal assemblages of plagioclase pyroxene olivine and fe ti oxides we infer from these results that unmixing of complex aluminosilicate liquids may be seriously kinetically hampered presumably by a nucleation barrier and thus conventional static experiments may not correctly reproduce it in the light of our centrifuge experiments immiscibility in the skaergaard intrusion could have started already at the transition from the lower to the middle zone thus magma unmixing might be an important factor in the development of the fe enrichment trend documented in the cumulates of the skaergaard layered series

ferric iron in catio3 perovskite as an oxygen barometer for kimberlitic magmas i experimental calibration a method to estimate the oxygen fugacity fo2 during the crystallization of kimberlites is developed using the fe content of catio3 perovskite pv a common groundmass phase in these rocks with increasing fo2 more fe exists in the kimberlitic liquid as fe3 and thus partitions into pv experiments to study the partitioning of fe between pv and kimberlite liquid were conducted at 100 kpa on simple and complex anhydrous kimberlite bulk compositions from 1130 to 13008c over a range of fo2 from nno 5 to nno 4 where nno is the nickel nickel oxide buffer and atnb and rare earth element ree contents in the starting materials of 0 5 wt and 1500 ppm respectively the partitioning of fe between pv and kimberlite liquid is influenced mostly by fo2 although the presence of nb increases the partition of fe3 into perovskite at a given t and fo2 multiple linear regression mlr of all the experimental data produces a relationship that describes the variation of fe andnbinpvwith fo2relative to thennobuffer

differentiation conditions of a basaltic magma from santorini and its bearing on the production of andesite in arc settings santorini volcano in the aegean region greece is characterized by andesitic to silicic dominated explosive activity and caldera forming eruptions sourced from magmatic reservoirs located at various structural levels beneath the volcano there is a good understanding of the silica rich magmatism of the island whereas the andesite dominated volcanism and the petrogenesis of the parental mafic magmas are still poorly understood to fill this gap we have performed crystallization experiments on a representative basalt from santorini with the aim of determining the conditions of differentiation pressure temperature volatile fugacities and the parental magma relationship with the andesitic eruptive rocks experiments were carried out between 975 and 1040 c in the pressure range 100 400 mpa fo2 from qfm to nno 3 5 where qfm is quartz fayalite magnetite and nno is nickel nickel oxide with h2omelt contents varying from saturation to nominally dry conditions the results show that basalt phenocrysts within the basalt crystallized at around 1040 c in a magma storage reservoir located at a depth equivalent to 200 400 mpa pressure with 3 5 wt dissolved h2o and fo2 around qfm comparison with the xenocryst and phenocryst assemblages of the upper scoria 1 andesite shows that andesitic liquids are produced by fractionation of a similar basalt at 1000 c and 400 mpa following 60 80 wt crystallization of an ol cpx plag ti mag opx 6 pig ilm assemblage with melt water contents around 4 6 wt at santorini the andesitic low viscosity and water rich residual liquids produced at these depths segregate from the parent basaltic mush and feed the shallow magma reservoirs eventually erupting upon mixing with resident magma changes in prevailing oxygen fugacity may control the tholeiitic calc alkaline character of santorini magmas explaining the compositional and mineralogical differences observed between the recent thyra and old eruptive products from akrotiri

melt inclusion evidence for mantle heterogeneity and magma degassing in the deccan large igneous province india abstract silicate melt inclusions mi trapped in minerals provide direct tools to evaluate source characteristics and magma evolution including magma chamber processes here we present results from the study of mis in basalts from the western ghats region of the deccan large igneous province lip in india the mis in plagioclase and clinopyroxene phenocrysts were analyzed the mis exhibit post entrapment modification by in situ crystal fractionation chemical interaction with the host phenocryst plagioclase or clinopyroxene degassing decrepitation and crystallization of daughter minerals during cooling the mis display variable silica sio2 41 68 wt low potassium and high fe ti contents corresponding to differentiation of basaltic to andesitic magma our data indicate h2o content of about 2 wt which is consistent with recent evidence for elevated primary h2o content in the deccan and other lips corresponding to elevated h2o in the lithospheric mantle and plumes passing through the mid mantle inheriting the hydrous nature

magnetite as an indicator of granite fertility and gold mineralization a case study from the xiaoqinling gold province north china craton abstract the xiaoqinling district in the southern margin of the north china craton is the second largest gold enriched area in china the huashan and wenyu plutons represent two typical mesozoic magmatic intrusions in this region and were coeval with the gold mineralization here we report the geochemistry and mossbauer spectral characteristics of magnetite from the two plutons with a view to explore the role of the granitic magmatism in the gold enrichment the results of epma and mossbauer spectroscopy suggest that the average values of fe2 fe3 in the magnetite from the two intrusions are lower than the standard value of 0 50 indicating an oxidizing environment the estimated oxygen fugacity is higher for the wenyu pluton than that of the huashan pluton which is also supported by the occurrence of hematite in the former and the distinct eu ce anomalies for magnetite from the two intrusions the sn content in magnetite indicates lower formation temperatures of the wenyu pluton as compared to that of the huashan pluton the results of la icp ms analysis demonstrate similar multi element variation patterns for the two intrusions titanium vs ni cr relationship suggests that the magnetite from the huashan pluton is of typical magmatic origin whereas that from the wenyu pluton shows both magmatic and hydrothermal signature the ni co ratio of magnetite from the wenyu granite is higher than that of the huashan granite which indicates a deeper source for the wenyu pluton the comparatively more favorable physico chemical conditions such as higher oxygen fugacity lower temperature as well as the involvement of deep sourced material are envisaged to have provided better metallogenic environment for generating the gold mineralization around the wenyu pluton

origin of the early permian wajilitag igneous complex and associated fe ti oxide mineralization in the tarim large igneous province nw china abstract the wajilitag igneous complex is part of the early permian tarim large igneous province in nw china and is composed of a layered mafic ultramafic intrusion and associated syenitic plutons in order to better constrain its origin and the conditions of associated fe ti oxide mineralization we carried out an integrated study of mineralogical geochemical and sr nd hf isotopic analyses on selected samples the wajilitag igneous rocks have an oib like compositional affinity similar to the coeval mafic dykes in the bachu region the layered intrusion consists of olivine clinopyroxenite coarse grained clinopyroxenite fine grained clinopyroxenite and gabbro from the base upwards fe ti oxide ores are mainly hosted in fine grained clinopyroxenite forsterite contents in olivines from the olivine clinopyroxenite range from 71 to 76 mol indicating crystallization from an evolved magma reconstructed composition of the parental magma of the layered intrusion is fe ti rich similar to that of the bachu mafic dykes syenite and quartz syenite plutons have end t values ranging from 1 4 to 2 9 identical to that for the layered intrusion they may have formed by differentiation of underplated magmas at depth and subsequent fractional crystallization magnetites enclosed in olivines and clinopyroxenes have cr2o3 contents higher than those interstitial to silicates in the layered intrusion this suggests that the cr rich magnetite is an early crystallized phase whereas interstitial magnetite may have accumulated from evolved fe ti rich melts that percolated through a crystal mush low v content in cr poor magnetite

magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace element discriminant diagrams when dealing with ancient subalkaline volcanic rocks the alkali total iron magnesium afm diagram is of limited use in assigning a tholeiitic versus calc alkaline affinity because these eleme

fe rich tholeiitic liquids and their cumulate products in the pleasant bay layered intrusion coastal maine fe rich tholeiitic liquids are preserved as chilled pillows and as the chilled base of a 27 meter thick macrorhythmic layer in the pleasant bay mafic silicic layered intrusion the compositions of olivine fo1 and plagioclase an13 8 in these extremely fine grained rocks suggest that they represent nearly end stage liquids that formed by fractionation of tholeiitic basalt their major element compositions 17 5 wt feot and 54 wt sio2 closely resemble highly evolved glasses in the loch ba ring dike and some recent estimates of end stage liquids related to the skaergaard layered intrusion and are consistent with recent experimental studies of tholeiite fractionation their trace element compositions are consistent with extensive earlier fractionation of plagioclase olivine clinopyroxene ilmenite magnetite and apatite the mineral assemblage of the chilled rocks olivine clinopyroxene quartz ilmenite and magnetite apatite saturation temperatures and very low fe3 fe2 indicate conditions of crystallization at temperatures of about 950 c and fo 2 about two log units below fmq cumulates that lie about 3 meters above the chilled base of the macrorhythmic layer contain cumulus plagioclase olivine clinopyroxene ilmenite apatite and zircon this mineral assemblage and the fe mg ratio in clinopyroxene cores suggest that this cumulate was in equilibrium with a liquid having a composition identical to that of the chilled margin which lies directly beneath it the high feot and low sio2 concentrations of this cumulate 23 3 and 45 8 wt respectively are comparable to those in late stage cumulates of the skaergaard and kiglapait intrusions this association of a chilled liquid and cumulate in the pleasant bay intrusion suggests that late stage liquids in tholeiitic layered intrusions may have been more sio2 rich than field based models suggest and lends support to recent experimental studies of tholeiite fractionation at low fo2 which indicate that saturation of an fe ti oxide phase should cause feot to decrease in the remaining liquid

kinetic controls on the partitioning of trace elements between silicate and sulfide liquids mass transfer between sulfide and silicate liquids is often discussed elements pge has resulted from liquation immiscible by reference to a mass ratio between hypothetical liquid reservoirs liquid phase separation of sulfide liquid from mafic or at equilibrium defined as r in an open system not at equilibrium ultramafic silicate magma a central assumption of modthe mass of silicate melt from which a growing sulfide droplet els of magmatic sulfide deposit formation is that the base appears to have scavenged chalcophile elements will depend on metals and pge are strongly partitioned into the sulfide diffusivities di and dfes of the element and of the fes component melt previous discussions of the process by which sulfide in the silicate melt respectively on the degree of supersaturation of liquids become enriched in chalcophile metals have fothe melt with fes c o on the radius a of the droplet and on the cused almost exclusively on models in which coexisting velocity v with which the droplet is advected through the melt so bodies of sulfide and silicate melt are considered to be that in equilibrium at all times the intent of this paper is to demonstrate that natural sulfide deposits preserved in igneous rocks will in many r 1 c fes o di 1 2 adiv dfes 1 2 adfesv instances record metal distributions that never attained equilibrium as a result of the kinetic constraints on metal chalcophile elements are expected to show inter element variations partitioning between phases the consequences are that in d spanning several orders of magnitude in some melts leading different elements will seem to show evidence for equito large inter element variations in effective r in a given sulfide libration at different silicate sulfide mass ratios within body these variations in effective r will lead to spatial separations single sulfide bodies i describe the time dependent evolubetween zones of maximum enrichment of chalcophile elements tion of metal distributions in silicate sulfide melt systems produced during fractional segregation of sulfide in layered intrusions starting with analytical solutions for simple boundary whereas it has proven impossible to model the generation of spatially conditions and then adapting them to more complex offset stratiform horizons in the australian munni munni layered systems as numerical models intrusion using equilibrium partition coefficients the present kinetic model reproduces the observed patterns with great fidelity

geochronology and geochemistry of porphyritic intrusions in the duolong porphyry and epithermal cu au district central tibet implications for the genesis and exploration of porphyry copper deposits abstract the duolong district in central tibet hosts a number of porphyry as well as high sulfidation epithermal copper gold deposits and prospects associated with voluminous calc alkaline volcanism and plutonism in this study we present new geochronological geochemical isotopic and mineralogical data for both economically mineralized and barren porphyritic intrusions from the duobuza and naruo porphyry cu au deposits zircon u pb analyses suggest the emplacement of economically mineralized granodiorite porphyry and barren granodiorite porphyry at naruo deposit took place at 119 8 1 4 ma and 117 2 0 5 ma respectively four molybdenite samples from the naruo deposit yield an isochron re os age of 119 5 3 2 ma indicating mineralization occurred synchronously with the emplacement of the early granodiorite porphyry at duobuza deposit the barren quartz diorite porphyry intruded at 119 5 0 7 ma and two economically mineralized intrusions intruded at 118 5 1 2 ma granodiorite porphyry and 117 5 1 2 ma quartz diorite porphyry respectively petrographic investigations and geochemical data indicate that all of the porphyritic intrusions were oxidized water rich and subduction related calc alkaline magmas zircons from the porphyritic intrusions have a wide range in the ehf 0 11 1 indicating that they were sourced from mixing of mantle derived mafic and crust derived felsic melts moreover the variation of trace element content of plagioclase phenocrysts indicates that the magma chambers were recharged by mafic magmas comparison of the composition of amphibole phenocrysts indicates the porphyry copper gold mineralization at duolong was generated in magma chambers at low crystallization temperatures and pressures 754 to 791 c 59 m to 73 mpa n 8 and under highly oxidizing conditions nno 2 2 to 2 7 n 8 in contrast barren intrusions were sourced from the magma chambers with higher crystallization temperatures and pressures 816 to 892 c 111 to 232 mpa n 22 that were less oxidizing nno 0 6 to 1 6 n 22 the requirement for a thermal contrast is supported by the declining of ti content in magnetite crystals in barren intrusions 12 550 to 34 200 ppm versus those from economically mineralized intrusions 600 to 3400 ppm moreover the v content in magnetite crystals from economically mineralized intrusions 990 to 2510 ppm is lower than those recorded from barren intrusions 2610 to 3510 ppm which might reflect the variation in oxidation state of the magma the calculated water solubility of the magma forming the economically mineralized intrusions 3 2 3 7 wt is lower than that of magma forming the barren intrusions 4 6 6 4 wt based on the chemical physical characteristics of economically mineralized magma our study suggests that the development of porphyry cu au mineralization at duolong was initiated by shallow level emplacement of a magma that crystallized at lower temperatures and pressures experimental studies show that copper and water solubilities in silicate melts decrease with falling temperatures and pressures indicating metals and ore forming fluids are more likely to be released from a magma reservoir emplaced at shallow crustal levels we propose the magnetite might be a convenient exploration tool in the search for porphyry copper mineralization because the variations in ti and v content of mineral concentrates and rock samples are indicative of barren versus mineralized intrusions

the peridotite plugs of rum crystal settling and fabric development in magma conduits the rum igneous complex contains numerous circular to elongate exposures of peridotite cumulates within the layered series and the country rock the extent of thermal effects on quartzo feldspathic country rock surrounding the mam tuath and west sgaorishal plugs demonstrates that these are pipe like bodies inclined at various angles to the vertical that remained at magmatic temperatures for periods of up to several months tabular olivine grains within the plugs preserve a weak sub horizontal fabric that is stronger in the plug centres than at their margins the olivine mode increases from 50 vol at the plug margins to 85 vol at the centre the spatial arrangement of the olivine grains is consistent with their being clustered with the increase in mode towards the plug centres achieved by a combination of overgrowth and mechanical re arrangement comparison of fabrics with those of the ard mheall peridotites of the rum western layered intrusion is consistent with porosity reduction in the ard mheall cumulates also having been primarily achieved by overgrowth and mechanical re arrangement compaction via intra crystalline deformation did not occur we suggest that the rum ultramafic plugs are deep level cross sections presenting the ultimate snap shots of volcanic conduits through which olivine rich magmas flowed for substantial periods probably giving rise to fire fountains of the kind associated with hawaiian eruptions the exposed parts of the plugs are now miniature cumulate bodies that developed in situ from the settling of olivine phenocrysts once flow had ceased within the conduit

laplace domain solutions for radial two zone flow equations under the conditions of constant head and partially penetrating well a mathematical model is presented for a constant head test performed in a partially penetrating well with a finite thickness skin the model uses a no flow boundary condition for the casing and a constant head boundary condition for the screen to represent the partially penetrating well the laplace domain solutions for the dimensionless flow rate at the wellbore and the hydraulic heads in the skin and formation zones are derived using the laplace and finite fourier cosine transforms the solutions of hydraulic heads have been shown to satisfy the governing equations related boundary conditions and continuity requirements for the pressure head and flow rate at the interface of the skin zone and undisturbed formation in addition an efficient algorithm for evaluating those solutions is also presented the dimensionless flow rates obtained from new solutions have been shown to be better than those of novakowski s solutions especially when the penetration ratio is large

formation of thick stratiform fe ti oxide layers in layered intrusion and frequent replenishment of fractionated mafic magma evidence from the panzhihua intrusion sw china 1 the panzhihua intrusion is one of the largest layered intrusions that hosts huge stratiform fe ti oxide layers in the central part of the emeishan large igneous province sw china up to 60 m thick stratiform massive fe ti oxide layers containing 85 modal of magnetite and ilmenite and overlying magnetite gabbro compose cyclic units of the lower zone of the intrusion the cyclic units of the middle zone consist of magnetite gabbro and overlying gabbro in these cyclic units contents of fe2o3 t tio2 and cr and fe3 ti4 ratio of the rocks decrease upward cr content of magnetite and forsterite percentage of olivine decrease as well the upper zone consists of apatite gabbro characterized by enrichment of incompatible elements e g 12 18 ppm la 20 28 ppm y and increasing of fe3 ti4 ratio from 1 3 to 2 3 upward these features indicate that the panzhihua intrusion was repeatedly recharged by more primitive magma and evolved magmas had been extracted calculations using melts indicate that extensive fractionation of olivine and clinopyroxene in deep level resulted in increasing fe and ti contents in the magma when these fe ti enriched magmas were emplaced along the base of the panzhihua intrusion fe ti oxides became an early crystallization phase leading to a residual magma of lower density we propose that the unusually thick stratiform fe ti oxide layers resulted from coupling of gravity settling and sorting of the crystallized fe ti oxides from fe ti enriched magmas and frequent magma replenishment along the floor of the magma chamber

experimental study of a kiglapait marginal rock and implications for trace element partitioning in layered intrusions abstract experiments on a chilled marginal rock from the kiglapait intrusion labrador have been performed in order to constrain the partitioning behaviour of major and trace elements during formation of kiglapait lower zone lz cumulates at 0 1 mpa and f o 2 close to fmq the liquidus is bracketed between 1225 and 1212 c and the only liquidus phases are plagioclase an 73 74 and olivine fo 82 85 in contrast lz troctolites contain fo 67 5 olivine and an 63 4 plagioclase plagioclase melt partition coefficients d s for li ti rb sr y zr ba la and eu determined by ion microprobe analysis of run products are similar to those for other basaltic systems but differ systematically from apparent d s calculated from bulk analyses of lz plagioclases and modelled liquid compositions obtained by summation the discrepancies in d s and phase compositions are inconsistent with diffusion controlled boundary layer growth crystallisation of trapped intercumulus liquid is quantitatively plausible however a the volume of liquid required to reconcile experimental and model d s 20 1 is larger than that estimated from observed proportions of intercumulus phases 11 2 and b this mechanism alone cannot reduce x an in lz plagioclases due to very slow al si interdiffusion the discrepancy between experiment and model is best resolved if the parental melt to lz cumulates was more evolved higher fe mg na ca ree and alkalis lower sr than the summed bulk composition in accord with a recent revision of the kiglapait fe mg based on olivine compositions

petrogenesis and metallogenesis of the wajilitag and puchang fe ti oxide rich intrusive complexes northwestern tarim large igneous province abstract the wajilitag and puchang intrusive complexes of the tarim large igneous province tlip are associated with significant resources of fe ti oxide ores these two mafic ultramafic intrusions show differences in lithology and mineral chemistry clinopyroxenite and melagabbro are the dominant rock types in the wajilitag complex whereas the puchang complex is generally gabbroic and anorthositic in composition with minor plagioclase bearing clinopyroxenites in the marginal zone disseminated fe ti oxide ores are found in the wajilitag complex and closely associated with clinopyroxenites whereas the puchang complex hosts massive to disseminated fe ti oxide ores mainly within its gabbroic rocks the wajilitag intrusive rocks are characterized by a restricted range of initial 87sr 86sr ratios 0 7038 0 7048 and positive end t 0 04 3 01 indicating insignificant involvement of continental crustal contamination the slightly higher initial 87sr 86sr ratios 0 7039 0 7059 and lower end t values 1 05 2 35 of the puchang intrusive rocks also suggest that the isotopic characteristics was controlled primarily by their mantle source rather than by crustal contamination both complexes have sr nd isotopic compositions close the neighboring kimberlitic rocks and their hosted mantle xenoliths in the tlip this indicates that the ferrobasaltic parental magmas were most probably originated from partial melting of a metasomatized subcontinental lithospheric mantle modified recently with subduction related materials by the impingement of the ascending mantle plume the recycled subduction related materials preserved in the lithospheric mantle could play a key role in the formation of the parental fe rich magmas in the context of an overall lip system the distinct variations in mineral assemblage for each complex and modeled results indicated that the wajilitag and puchang complexes experienced different crystallization path fe ti oxides in wajilitag joined the liquidus earlier in the crystallization sequence especially relative to the crystallization of plagioclase this is attributed to the relatively high tfeo tio2 and initial h2o contents of the parental magma in combination with definitive field and petrological evidence the enrichment of highly incompatible elements e g zr hf nb and ta and the depletion of rare earth elements in the fe ti oxide ores is consistent with the plausible interpretation that the ores could be formed by fractional crystallization and crystal accumulation of the fe ti oxide crystals from the ferrobasaltic parental magmas a considerable amount of the fe ti oxides in the puchang has transported and sunk from higher up in the chamber to the underlying unconsolidated silicate crystal pile the highly dense fe ti oxide crystal slurries further tended to effective accumulate fe ti oxides to form high grade fe ti oxide ore bodies and subsequent rapid collapse and intrusive into lower lithologies within the complex under a h2o rich environment during the late stage of magmatic differentiation the development of massive fe ti oxide ores in the case of the puchang could plausibly result from a combination of the protracted differentiation history of a fe highly enriched parental magma and the later addition of external h2o from the country rocks e g carbonates to the slowly cooling magma chamber

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

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

oxygen isotope trajectories of crystallizing melts insights from modeling and the plutonic record elevated oxygen isotope values in igneous rocks are often used to fingerprint supracrustal alteration or assimilation of material that once resided near the surface of the earth the 18 o value of a melt however can also increase through closed system fractional crystallization in order to quantify the change in melt 18 o due to crystallization we develop a detailed closed system fractional crystallization mass balance model and apply it to six experimentally and naturally determined liquid lines of descent llds which cover nearly complete crystallization intervals melt fractions of 1 to 0 1 the studied llds vary from anhydrous tholeiitic basalts to hydrous high k and calc alkaline basalts and are characterized by distinct melt temperature sio 2 trajectories as well as crystallizing phase relationships our model results demonstrate that melt fraction temperature sio 2 relationships of crystallizing melts which are strongly a function of magmatic water content will control the specific 18 o path of a crystallizing melt hydrous melts typical of subduction zones undergo larger increases in 18 o during early stages of crystallization due to their lower magmatic temperatures greater initial increases in sio 2 content and high temperature stability of low 18 o phases such as oxides amphibole and anorthitic plagioclase versus albite conversely relatively dry tholeiitic melts only experience significant increases in 18 o at degrees of crystallization greater than 80 total calculated increases in melt 18 o of 1 0 to 1 5 can be attributed to crystallization from 50 to 70 wt sio 2 for modeled closed system crystallizing melt compositions as an example application we compare our closed system model results to oxygen isotope mineral data from two natural plutonic sequences a relatively dry tholeiitic sequence from the upper and upper main zones uumz of the bushveld complex south africa and a high k hydrous sequence from the arc related dariv igneous complex mongolia these two sequences were chosen as their major and trace element compositions appear to have been predominantly controlled by closed system fractional crystallization and their llds have been modeled in detail we calculated equilibrium melt 18 o values using the measured mineral 18 o values and calculated mineral melt fractionation factors increases of 2 3 and 1 1 5 in the equilibrium melts are observed for the dariv igneous complex and the uumz of the bushveld complex respectively closed system fractional crystallization model results reproduce the 1 increase observed in the equilibrium melt 18 o for the bushveld uumz whereas for the dariv igneous complex assimilation of high 18 o material is necessary to account for the increase in melt 18 o values assimilation of evolved supracrustal material is also confirmed with sr and nd isotope analyses of clinopyroxene from the sequence beginning with a range of mantle derived basalt 18 o values of 5 7 pristine mantle to 7 0 heavily subduction influenced mantle our model results demonstrated that high silica melts i e granites with 18 o of up to 8 5 can be produced through fractional crystallization alone lastly we model the zircon melt 18 o fractionations of different llds emphasizing their dependence on the specific sio 2 t relationships of a given crystallizing melt wet relatively cool granitic melts will have larger zircon melt fractionations potentially by 1 5 compared to hot dry granites therefore it is critical to constrain zircon melt fractionations specific to a system of interest when using zircon 18 o values to calculate melt 18 o

an experimental study of the influence of oxygen fugacity on fe ti oxide stability phase relations and mineral melt equilibria in ferro basaltic systems

compositional and kinetic controls on liquid immiscibility in ferrobasalt rhyolite volcanic and plutonic series we present major element compositions of basalts and their differentiation products for some major tholeiitic series the dry low pressure liquid lines of descent are shown to approach or intersect the experimentally defined compositional space of silicate liquid immiscibility ferrobasalt rhyolite unmixing along tholeiitic trends in both volcanic and plutonic environments is supported by worldwide occurrence of immiscible globules in the mesostasis of erupted basalts unmixed melt inclusions in cumulus phases of major layered intrusions such as skaergaard and sept iles and oxide rich ferrogabbros closely associated with plagiogranites in the lower oceanic crust liquid immiscibility is promoted by low pressure anhydrous fractional crystallization that drives the low al2o3 high feo liquids into the two liquid field kinetic controls can be important in the development of two liquid separation the undercooling that occurs at the slow cooling rates of plutonic environments promotes early development of liquid immiscibility at higher temperature in contrast rapid cooling in erupted lavas leads to large undercoolings and liquid immiscibility develops at significantly lower temperatures unmixing leads to the development of a compositional gap characterized by the absence of intermediate compositions a feature of many tholeiitic provinces the compositions of experimental unmixed silica rich melts coincide with those of natural rhyolites and plagiogranites with high feotot and low al2o3 suggesting the potential role of large scale separation of immiscible si rich liquid in the petrogenesis of late stage residual melts no trace of the paired ferrobasaltic melt is found in volcanic environments because of its uneruptable characteristics instead fe ti p rich gabbros are the cumulate products of immiscible fe rich melts in plutonic settings the immiscibility process may be difficult to identify because both melts crystallize the same phases with the same compositions the two liquids might form incompletely segregated emulsions so that both liquids continue to exchange as they crystallize and remain in equilibrium even if segregated both melts evolve on the binodal surface and exsolve continuously with decreasing temperature the two liquids do not differentiate independently and keep crystallizing the same phases with differentiation further evolution by fractional crystallization potentially drives the bulk liquid out of the twoliquid field so that very late stage liquids could evolve into the single melt phase stability field

post stack stratigraphic inversion workflow applied to carbon dioxide storage application to the saline aquifer of sleipner field in the norwegian north sea the sleipner field produces gas with a high co 2 content for environmental reasons since 1996 more than 11 mt of this carbon dioxide co 2 have been injected in the utsira sand saline aquifer located above the hydrocarbon reservoir a series of seven 3d seismic surveys were recorded to monitor the co 2 plume evolution with this case study time lapse seismics have been shown to be successful in mapping the spread of co 2 over the past decade and to ensure the integrity of the overburden stratigraphic inversion of seismic data is currently used in the petroleum industry for quantitative reservoir characterization and enhanced oil recovery now it may also be used to evaluate the expansion of a co 2 plume in an underground reservoir the aim of this study is to estimate the p wave impedances via a bayesian model based stratigraphic inversion we have focused our study on the 1994 vintage before co 2 injection and the 2006 vintage carried out after a co 2 injection of 8 4 mt in spite of some difficulties due to the lack of time lapse well log data on the interest area the full application of our inversion workflow allowed us to obtain for the first time to our knowledge 3d impedance cubes including the utsira sand these results can be used to better characterize the spreading of co 2 in a reservoir with the post stack inversion workflow applied to co 2 storage we point out the importance of the a priori model and the issue to obtain coherent results between sequential inversions of different seismic vintages the stacking velocity workflow that yields the migration model and the a priori model specific to each vintage can induce a slight inconsistency in the results

trapped intercumulus liquid in the main zone of the eastern bushveld complex south africa lateral variations in the amount of trapped intercumulus liquid in the main zone of the eastern bushveld complex are constrained by new sr isotopic whole rock and mineralogical data from three profiles that are separated laterally by ca 100 km and represent thicknesses of 551 1 127 m of main zone gabbronorites below the pyroxenite marker an analysis of the an contents 100 ca ca na of plagioclase cores within the thornhill north roossenekal and stoffberg south profiles show similar systematic up section variations from an66 to an59 in contrast both the an contents of bulk plagioclase separates and the mg numbers 100 mg mg fet of orthopyroxenes show pronounced lateral variations from thornhill an67 61 mg 67 61 through roossenekal an64 58 mg 64 55 to stoffberg an59 55 mg 59 50 these mineralogical variations are interpreted to be the result of reaction between cumulus minerals and an increasing amount of trapped liquid from north to south modelling of the trapped liquid shift of orthopyroxene compositions suggests that the amount of trapped liquid in the cumulates increased from near 0 at thornhill through 10 30 at roossenekal to 30 45 at stoffberg a two to eightfold southward increase in whole rock concentrations of p ti y zr and ba is consistent with the trapped liquid model however the 14 fold increase in rb from thornhill to stoffberg is too great to be accounted for by trapped liquid alone but can be explained by local assimilation of partial melts of the country rock constant initial 87sr 86sr isotopic ratios of main zone plagioclase separates 0 7081 0 7085 in all the three profiles do not preclude assimilation of adjacent basaltic to rhyolitic country rock with initial ratios between 0 6924 0 7096 the southward increase in the amount of trapped liquid is ascribed to an increased cooling rate by enhanced heat loss and partial assimilation of country rock xenoliths in the distal cumulate sequence at stoffberg

the fedorivka layered intrusion korosten pluton ukraine an example of highly differentiated ferrobasaltic evolution abstract this study documents the petrography and whole rock major and trace element geochemistry of 38 samples mainly from a drill core through the entire fedorivka layered intrusion korosten pluton as well as mineral compositions microprobe analyses and separated mineral fraction analyses of plagioclase ilmenite magnetite and apatite of 10 samples the fedorivka layered intrusion can be divided into 4 lithostratigraphic units a lower zone lz 72 m thick a main zone mz 160 m thick and an upper border zone itself subdivided into 2 sub zones ubz2 40 m thick ubz1 50 m thick igneous lamination defines the cumulate texture but primary cumulus minerals have been affected by trapped liquid crystallization and subsolidus recrystallization the dominant cumulus assemblage in mz and ubz2 is andesine an39 42 iron rich olivine fo32 42 augite en29 35fs24 29wo42 44 ilmenite hem1 6 ti magnetite usp52 78 and apatite the data reveal a continuous evolution from the floor of the intrusion lz to the top of mz due to fractional crystallization and an inverse evolution in ubz resulting from crystallization downwards from the roof the whole rock fe mg ratio and incompatible element contents e g rb nb zr ree increase in the fractionating magma whereas compatible elements e g v cr steadily decrease the intercumulus melt remained trapped in the ubz cumulates due to rapid cooling and lack of compaction and cumulus mineral compositions re equilibrated e g olivine fe ti oxides in lz the intercumulus melt was able to partially or totally escape the major element composition of the mz cumulates can be approximated by a mixing linear relationship between a plagioclase pole and a mafic pole the latter being made up of all mafic minerals in nearly constant relative proportions by analogy with the ferrobasaltic jotunitic liquid line of descent defined in rogaland s norway and its conjugated cumulates occurring in the transition zone of the bjerkreim sokndal intrusion rogaland a monzonitic 57 sio2 melt is inferred to be in equilibrium with the mz cumulates the conjugated cumulate composition falls within error on the locus of cotectic compositions fixed by the 2 pole linear relationship ulvospinel is the only ti phase in some magnetites that have been protected from oxidation quilf equilibria in these samples show that magnetite and olivine in mz have retained their liquidus compositions during subsolidus cooling this permits calculation of liquidus fo2 conditions which vary during fractionation from fmq 0 7 to 1 4 log units low fo2 values are also evidenced by the late appearance of cumulus magnetite fo42 and the high v3 content of the melt reflected in the high v content of the first liquidus magnetite up to 1 85 v

silicate liquid immiscibility within the crystal mush late stage magmatic microstructures in the skaergaard intrusion east greenland late stage microstructures developed during the last stages of solidification of the skaergaard intrusion comprise a wide array of reactive and non reactive intergrowths reactive microstructures ascribed to open system behaviour include serrated grain boundaries between pyroxene and plagioclase primocrysts fish hook pyroxenes and mafic symplectites they form by the addition of fe and ca and removal of alkalis and silica other microstructures include those formed by internally generated redox reactions between olivine fe ti oxides and pyroxene non reactive microstructures include closely spatially associated granophyric intergrowths and previously undescribed ilmenite rich intergrowths that are interpreted as a consequence of crystallization of separated conjugate immiscible liquids the open system reactive microstructures occur predominantly in the cumulates on the chamber floor appearing in lzb and disappearing to be replaced by a granophyre ilmenite rich intergrowth association in the upper zone they are not common in the marginal border series their distribution mirrors that of efficient expulsion of trapped liquid and can be attributed to the gravitationally driven loss of a si rich immiscible component from the interstitial liquid the loss of the si rich component causes the remaining fe rich liquid to react with the primocrysts bulk rock major element data are consistent with little or no preferential loss of the si rich liquid from the mush but the resolution of the available data is not sufficient to assess the effect of this relative movement on the liquid line of descent of the bulk magma the first appearance of the paired conjugate non reactive intergrowths in mz marginal border series points to the early onset of immiscibility in the bulk liquid

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

plagioclase in the skaergaard intrusion part 1 core and rim compositions in the layered series the anorthite content of plagioclase grains xan in 12 rocks from the layered series of the skaergaard intrusion has been studied by electron microprobe typically 30 core and 70 rim analyses per thin section mean core compositions vary continuously from an66 at the base of the layered series lza to an32 30 at the top on the other hand crystal rims are of approximately constant composition an50 1 from the lza to the lower middle zone mz above the mz core and rim compositions generally overlap profiles across individual plagioclase grains from the lower zone show that most crystals have an external zone buffered at xan 50 1 the simplest explanation for these features is that during postcumulus crystallization in the lower zone interstitial liquids passed through a density maximum this interpretation is consistent with proposed liquid lines of descent that predict silica enrichment of the liquid associated with the appearance of cumulus magnetite

partial least squares discriminant analysis of trace element compositions of magnetite from various vms deposit subtypes application to mineral exploration abstract the petrography and mineral chemistry of magnetite from fifteen volcanogenic massive sulfide vms deposits in canada and the lasail vms deposit in oman as well as from two vms associated banded iron formations bif austin brook new brunswick canada and izok lake nunavut canada were investigated using optical microscopy electron probe micro analyzer epma and laser ablation inductively coupled plasma mass spectrometry la icp ms the method of robust estimation for compositional data robcompositions was applied to investigate geochemical censored data among thirty seven elements analyzed by epma and or la icp ms in magnetite from the studied deposits bedrock lithologies only the results for si ca zr al mg ti zn co and ni contain pls da shows that variable compositions of magnetite slightly discriminate different studied deposits bedrock lithologies the geochemical observations suggest that the variation in magnetite chemistry from different vms settings might be sourced from differences in 1 the composition and temperature of parental magmas or hydrothermal fluids 2 the composition of host bedrocks 3 the composition of co forming minerals and 4 oxygen fugacity pls da distinguishes magnetite compositions from the studied vms deposits and bifs from that of the other ore deposit types including ni cu porphyry cu mo au iron oxide copper gold iron oxide apatite and the bayan obo ree fe nb deposit magnetite from the vms settings on average contains lower concentrations of si zr al mg ti zn co and ni relative to that from the other mineral deposit types pls da of magnetite data from vms deposits and bifs of the bathurst mining camp as well as pls da of magnetite compositions from various mineral deposit types yield discrimination models for application to mineral exploration for vms deposits using indicator minerals in quaternary lithified sedimentary rocks

prediction of plagioclase melt equilibria in anhydrous silicate melts at 1 atm many models for plagioclase melt equilibria have been proposed over the past 30 years but the focus is increasingly on the effects of water content and pressure however many geological and petrological applications concern low pressure and low water systems such as the differentiation of large terrestrial basaltic magma chambers and lunar and asteroidal magmatism there is therefore a justified need to quantify the influence of anhydrous liquid composition on the composition of equilibrium plagioclase at 1 atm with this in mind a database of over 500 experimentally determined plagioclase liquid pairs has been created the selected low pressure anhydrous experiments include both natural and synthetic liquids whose compositions range from basalt to rhyolite four equations are proposed derived from this data the first is based on a thermodynamically inspired formalism explicitly integrating the effect of temperature this equation uses free energies and activities of crystalline anorthite available from the literature for the activity of anorthite in the liquid phase it is found that current models of the activity of individual oxides are insufficient to account for the experimental results we have therefore derived an empirical expression for the variation of anorthite activity in the liquid as a function of melt composition based upon inversion of the experimental data using this expression allows the calculation of plagioclase composition with a relative error less than 10 however in light of the fact that temperature is not necessarily known for many petrological applications an alternative set of t independent equations is also proposed for this entirely empirical approach the database has been divided into three compositional groups treated independently for regression purposes mafic ultramafic alkali rich mafic ultramafic and intermediate felsic this separation into distinct subgroups was found to be necessary to maintain errors below acceptable limits but results across group boundaries were found to be comparable overall 50 of plagioclase compositions are predicted to within 2 of the experimentally derived value and 90 to within 5 representing a significant improvement over existing models

pre eruptive conditions of the huerto andesite fish canyon system san juan volcanic field colorado influence of volatiles c o h s on phase equilibria and mineral composition crystallization experiments at 400 mpa oxidized condition logfo2 nno 1 where nno is nickel nickel oxide buffer and over a range of temperatures 850 950 c and fluid composition xh2oin 0 3 1 have been carried out to constrain the storage conditions of the sulphur rich magma of the huerto andesite an anhydrite pyrrhotite and s rich apatite bearing post fish canyon tuff mafic lava the results are used to evaluate the role of fluids released from the crystallization of magmas such as the huerto andesite on the remobilization of the largely crystallized dacitic fish canyon magma body experiments were performed using the natural andesitic bulk composition with and without added sulphur the presence of sulphur slightly affects the phase equilibria by changing the phase proportions stability fields of plagioclase pyroxenes and ilmenite and also affects the plagioclase composition phase equilibria and mineral composition data indicate that the magma may have contained 4 5 wt water in the melt and that the pre eruptive temperature was 875 25 c assuming that the magma was in equilibrium with a fluid phase the co2 concentration of the melt is estimated to be in the range 2000 4000 ppm at 400 mpa before eruption the andesite had an oxidation state very close to or slightly within the co stability field of anhydrite pyrrhotite at nno 1 1 at these conditions the sulphur content in the melt is 500 ppm assuming open system degassing resulting from continuing crystallization at depth most of the co2 dissolved in the andesitic melt should be released after the crystallization of 10 vol of the magma corresponding to a cooling from 875 to 825 850 c thus the fluids released owing to crystallization processes should be mainly composed of water at temperatures below 825 c

evolution of a permian intraoceanic arc trench system in the solonker suture zone central asian orogenic belt china and mongolia abstract the identification of a fossil arc trench system from the ophiolite decorated solonker suture zone in the southernmost central asian orogenic belt caob enables us to constrain the timing of pre subduction extension ca 299 290 ma subduction initiation ca 294 280 ma ridge trench collision ca 281 273 ma and slab break off ca 255 248 ma in the permian a fraction of proto arc crust ca 45 km long up to 8 km wide is preserved as a volcanic plutonic sequence and is juxtaposed against a wide ca 30 80 km forearc melange this proto arc crust comprises two distinct magma series island arc tholeiite iat and mid ocean ridge basalt morb both of which have strong supra subduction zone ssz geochemical signatures zircons from a gabbro and a plagiogranite yielded weighted mean 206pb 238u ages of 284 0 4 0 and 288 0 6 0 ma the forearc melange consists of numerous ophiolite fragments and continental margin derived olistoliths blocks that predate the ophiolite the olistoliths are best represented by a gabbroic block 291 8 2 3 ma that contains granite xenoliths 312 6 1 8 and 313 6 3 1 ma other dated blocks include a trondhjemite 323 9 2 7 ma a gabbro 296 6 1 7 ma and a tonalite 294 9 2 4 ma small bodies of diabase andesite and diorite in the forearc melange exhibit a wide variety of geochemical signatures we dated zircons from an n morb like diabase 274 4 2 5 ma an e morb like diabase 252 5 2 3 ma a transitional sanukitoid adakite andesite 250 2 2 4 ma a sanukitoid high mg diorite 251 8 1 1 ma and an anorthosite 252 2 1 7 ma the n morb like diabase contains ca 301 394 ma zircon xenocrysts suggesting assimilation of trench sediments when a spreading ridge intersected a trench the other dated rocks simultaneously formed near the permian triassic boundary and captured abundant zircon xenocrysts ca 269 295 ma ca 301 495 ma and ca 923 2501 ma our new formation ages constrain a magmatic episode in response to slab break off beneath a fossil forearc in a young post collisional setting and the youngest xenocryst ages ca 269 273 ma may define the maximum depositional age of trench sediments

microstructures and late stage magmatic processes in layered mafic intrusions symplectites from the sept iles intrusion quebec canada replacive symplectites vermicular intergrowths of two or more minerals are an important feature of layered igneous intrusions recording evidence of late stage reactions between interstitial liquid and crystals they are common throughout the layered series of the 564 ma sept iles layered intrusion in quebec canada and fall into three types oxy symplectites type i symplectites and type ii symplectites oxy symplectites are comprised of magnetite and orthopyroxene nucleate on olivine primocrysts and form via the reaction olivine o2 orthopyroxene magnetite type i symplectites of which there are 3 distinct categories are comprised of anorthitic plagioclase with pyroxene amphibole or olivine vermicules grow from primocryst oxide grains and replace primary plagioclase and type ii symplectites of which there are 2 distinct categories are comprised of anorthitic plagioclase with orthopyroxene amphibole vermicules grow from primocryst olivine

on the horizontal well pumping tests in anisotropic confined aquifers a method that directly solves the boundary problem of flow to a horizontal well in an anisotropic confined aquifer is provided this method solves the point source problem first and then integrates the point source solution along the horizontal well axis to obtain the horizontal well solution the short and long time approximations of drawdowns are discussed and are utilized in the semilog analysis of the drawdown a closed form analytical solution of geometrical skin effect at the wellbore is derived type curves and derivative type curves of horizontal pumping wells are generated using the chow program this program also calculates the drawdown at any given observation well at any given time the horizontal well type curves are different from the vertical well type curves at early time reflecting the different nature of flow to a horizontal well and to a vertical well the horizontal well type curves converge to the vertical well type curves at late time showing the similar nature of flow to a horizontal well and to a vertical well at late time the sensitivity of the type curves and derivative type curves on monitoring well location aquifer anisotropy horizontal well depth and horizontal well length is tested these type curves and derivative type curves can be used in the matching point method for interpreting the pumping test data

genesis of chating cu au deposit in the middle lower yangtze river metallogenic belt eastern china implications from magnetite and biotite geochemistry abstract porphyry deposits developed in intracontinental settings have some geological characteristics that differ from those developed in arc related continental margins the chating deposit is a newly discovered cu au deposit in the middle lower yangtze river metallogenic belt mlyb eastern china we carried out detailed petrographic observations and major and trace element analyses of different types of magnetite and biotite from the host quartz diorite porphyry and different alteration zones in chating to elucidate the genesis of chating deposit alteration types in chating include skarn sodic calcic potassic and phyllic and copper mineralization is closely associated with potassic alteration of quartz diorite porphyry the different types of magnetite and biotite at chating show distinctive geochemical characteristics higher ti and al in magmatic magnetites and biotites compared to the hydrothermal minerals indicate higher temperature and pressure in the quartz diorite porphyry higher v in magmatic magnetites and lower xmg in magmatic biotites indicate higher fo2 similar mineral geochemistry from typical worldwide porphyry deposits for example al2o3 tio2 feot mgo na2o iv f and iv cl contents in biotite and ni cr ti al sn and ga in magnetite indicate a predominately magmatic fluid source differences in si ca co ni mg and mn in different types of magnetite and mno cao sio2 differences in two types of biotite from typical porphyry copper deposits show the influence of external fluids moreover high iv f values and low iv cl values in biotites demonstrate that the magmatic hydrothermal system in chating was enriched in cl and lacked f consistent with the importance of cl in the transport of cu based on different discrimination diagrams for magnetite such as ni cr versus ti ni cr mn versus ti v and al mn versus ti v and the geochemical similarities of biotite from chating and other porphyry deposits combined with the similarity of alteration assemblages we conclude that chating has porphyry cu au affinities but the hydrothermal system was affected by external fluids in contrast to more typical subduction related porphyry deposits

crystallization sequence and magma chamber processes in the ferrobasaltic sept iles layered intrusion canada the sept iles layered intrusion quebec canada 564 ma is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro and an upper border series with anorthosite capped by cupolas of a type granite chilled margin compositions suggest a ferrobasaltic parental magma close to that of the skaergaard intrusion but much richer in iron and titanium samples from drill cores and surface sampling of the 4 7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 fe ti oxide layers cm to m thick and many anorthositic autolithic blocks the sequence of crystallization in the layered series is plagioclase an72 34 and olivine fo75 21 followed by magnetite and ilmenite then ca rich pyroxene and finally apatite an olivine gap is observed between fo66 and fo59 the saturation of fe ti oxides before ca rich pyroxene is interpreted to be the result of the high feot and tio2 contents and the low cao content of the parental magma contamination by old continental crust has occurred during crystallization of the layered series as indicated by sr isotopic compositions 87sr 86sr564 0 70360 0 70497 the differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases cr content of magnetite and lower sr isotope ratios these reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma the author 2010 published by oxford university press all rights reserved for permissions please e mail journals permissions oxfordjournals org

the aurora volcanic field california nevada oxygen fugacity constraints on the development of andesitic magma the aurora volcanic field located along the northeastern margin of mono lake in the western great basin has erupted a diverse suite of high k and shoshonitic lava types with 48 to 76 wt sio2 o ver the last 3 6 million years there is no correlation between the age and composition of the lavas three quarters of the volcanic field consists of evolved 4 wt mgo basaltic andesite and andesite lava cones and flows the majority of which contain sparse euhedral phenocrysts that are normally zoned there is no evidence of mixed hybrid magmas the average eruption rate over this time period was 200 m 3 ykm 2 yyear which is typical of con tinental arcs and an order of magnitude lower than that for the slow spreading mid atlantic ridge all of the au rora lavas display a trace element signature common to subduction related magmas as exemplified by baynb ratios between 52 and 151 pre eruptive water contents ranged from 1 5 wt in plagioclase rich two pyroxene andesites to 6 wt in a single hornblende lamprophyre and several biotite hornblende andesites calculated oxygen fugacities fall within 0 4 and 12 4 log units of the ni nio buffer the aurora potassic suite follows a classic calc alkaline trend in a plot of feo t ymgo vs sio 2 and displays linear decreasing trends in feo t and tio2 with sio2 content suggesting a prominent role for fe ti oxides during differentiation however develop ment of the calc alkaline trend through fractional crys tallization of titanomagnetite would have caused the residual liquid to become so depleted in ferric iron that its oxygen fugacity would have fallen several log units below that of the ni nio buffer nor can fractionation of hornblende be invoked since it has the same effect as titanomagnetite in depleting the residual liquid in ferric iron together with a thermal stability limit that is lower than the eruption temperatures of several andesites 1040 10808c derived from two pyroxene ther mometry unless some progressive oxidation process occurs fractionation of titanomagnetite or hornblende cannot explain a calc alkaline trend in which all erupted lavas have oxygen fugacites the ni nio buffer in con trast to fractional crystallization closed system equi librium crystallization will produce residual liquids with an oxygen fugacity that is similar to that of the initial melt however the eruption of nearly aphryic lavas ar gues against tapping from a magma chamber during equilibrium crystallization a process that requires crys tals to remain in contact with the liquid a preferred model involves the accumulation of basaltic magmas at the mantle crust interface which solidify and are later remelted during repeated intrusion of basalt as an end member case closed system equilibrium crystallization of a basalt followed by equilibrium partial melting of the gabbro will produce a calc alkaline evolved liquid namely high sio 2 and low feo t ymgo with a relative fo2 corrected for the effect of changing temperature that is similar to that of the initial basalt differentiation of the aurora magmas by repeated partial melting of previous underplates in the lower crust rather than by crystal fractionation in large stable magma chambers is consistent with the low eruption rate at the aurora vol canic field

magnesium isotopic evidence for chemical disequilibrium among cumulus minerals in layered mafic intrusion abstract magnesium isotopic compositions of olivine clinopyroxene and ilmenite from the baima intrusion sw china for the first time are investigated to constrain the magnitude and mechanisms of mg isotope fractionation among cumulus minerals in layered mafic intrusions and to evaluate their geological implications olivine and clinopyroxene have limited mg isotope variations with 26 mg ranging from 0 33 to 0 05 and from 0 29 to 0 13 respectively similar to those of mantle xenolithic peridotites by contrast ilmenites display extremely large mg isotopic variation with 26 mg ranging from 0 50 to 1 90 the large inter mineral fractionations of mg isotopes between ilmenite and silicates may reflect both equilibrium and kinetic processes a few ilmenites have lighter mg isotopic compositions than coexisting silicates and contain high mgo contents without compositional zoning indicating equilibrium fractionation the implication is that the light mg isotopic compositions of lunar high ti basalts may result from an isotopically light source enriched in cumulate ilmenites on the other hand most ilmenites have heavy mg isotopic compositions coupled with high mgo concentration and chemical zoning which can be quantitatively modeled by kinetic mg isotope fractionations induced by subsolidus mg fe exchange between ilmenite and ferromagnesian silicates during the cooling of the baima intrusion the extensive occurrence of kinetic mg isotope fractionation in ilmenites implies the possibility of widespread compositional disequilibrium among igneous minerals in magma chambers consequently disequilibrium effects need to be considered in studies of basaltic magma evolution magma chamber processes and magmatic fe ti oxide ore genesis

experimental determination of coexisting iron titanium oxides in the systems fetialo fetialmgo fetialmno and fetialmgmno at 800 and 900 c 1 4 kbar and relatively high oxygen fugacity a synthetic low melting rhyolite composition containing tio2 and iron oxide with further separate additions of mgo mno and mgo mno was used in hydrothermal experiments to crystallize ilm hem and usp mt solid solutions at 800 and 900 c under redox conditions slightly below nickel nickel oxide nno to approx 3 log 10 f text o 2 units above the nno oxygen buffer these experiments provide calibration of the feti oxide thermometer oxygen barometer at conditions of temperature and oxygen fugacity poorly covered by previous equilibrium experiments isotherms for our data in roozeboom diagrams of projected usp vs ilm show a change in slope at 60 ilm consistent with the second order transition from feti ordered ilm to feti disordered ilm hem this feature of the system accounts for some but not all of the differences from earlier thermodynamic calibrations of the thermobarometer in rhyolite containing 1 0 wt mgo 0 8 wt mno or mgo mno usp mt crystallized with up to 14 of aluminate components and ilm hem crystallized with up to 13 geikielite component and 17 pyrophanite component relative to the fetialo system these components displace the ferrite components in usp mt and the hematite component in ilm hem as a result projected contents of ulvospinel and ilmenite are increased these changes are attributed to increased non ideality along joins from end member hematite and magnetite to their respective mg and mn bearing titanate and aluminate end members the compositional shifts are most pronounced in ilm hem in the range ilm50 80 a solvus region where the chemical potentials of the hematite and ilmenite components are nearly independent of composition the solvus gap widens with addition of mg and even further with mn the bacon hirschmann correlation of mg mn in usp mt and coexisting ilm hem is displaced toward increasing mg mn in ilmenite with passage from ordered ilmenite to disordered hematite orthopyroxene and biotite crystallized in experiments with added mgo and mgo mno their x fe varies with log 10 f text o 2 and t consistent with equilibria among ferrosilite annite and ferrite components and the chemical potentials of sio2 and orthoclase in the liquid experimental equilibration rates increased in the order opx bt ilm hem usp mag

differentiation of ferro basaltic magmas under conditions open and closed to oxygen implications for the skaergaard intrusion and other natural systems because processes such as fractional crystallization and crystallization under conditions closed to oxygen are difficult to simulate in the laboratory there is a need for quantitative models of magma crystallization behaviour comparison of experimental data on an iron rich basaltic composition with predictions of the melts free energy minimization algorithm shows that although liquidus temperatures and silicate mineral equilibria are predicted relatively well the saturation of fe ti oxides is not we have used the same experimental data to construct an alternative crystallization model based on known equilibrium phase relations mineral melt partitioning of major elements and mass balance constraints the model is used to explore the consequences of equilibrium and fractional crystallization in systems open and closed to oxygen liquid lines of descent for perfect equilibrium and perfect fractional crystallization are predicted to be very similar in a system open to oxygen the model predicts that magnetite saturation leads to strongly decreasing iron and increasing silica contents of residual liquids whereas systems closed to oxygen crystallize less abundant magnetite leading to a less pronounced iron depletion in the liquid predicted bulk solid compositions and variations offo with falling temperature agree well with those observed or inferred from the cumulates of the skaergaard intrusion but none of the predicted liquid lines of descent are consistent with the extreme iron enrichment proposed for this intrusion based on mass balance calculations compositional factors such as water and phosphorus are not thought to be the source of the discrepancy as the cumulates of the basistoppen sill which closely resemble those of skaergaard may be used to calculate a liquid line of descent in agreement with that predicted by the model for fractional crystallization closed to oxygen a comparison of the predicted t io paths and liquid lines of descent with those inferred from natural systems suggests that volcanic centres such as iceland and hawaii evolve under conditions open to oxygen whereas evidence from plutonic environments e g skaergaard and kiglapait layered intrusions suggests that they evolved under conditions more closed to oxygen the compositional evolution of the melt phase in volcanic and plutonic systems may therefore be different although the results of this study suggest that magnetite saturation will limit fe enrichment in all environments to 20wt feo consistent with enrichments reported for volcanic glasses

origin of fe ti oxide ores in mafic intrusions evidence from the panzhihua intrusion sw china economicconcentrationsof fe ti oxidesoccuras massive conform able lenses or layers in the lower part of the panzhihua intrusion emeishan large igneous province sw china mineral chemistry textures and quilfequilibria indicate that oxides in rocks of theintrusion were subjected to extensive subsolidus re equilibration andexsolution the primary oxide reconstructed from compositions oftitanomagnetite in the oresand associated intergrowths isan alumi nous titanomagnetite usp

disequilibrium iron isotopic fractionation during the high temperature magmatic differentiation of the baima fe ti oxide bearing mafic intrusion sw china abstract iron isotopic compositions of olivine clinopyroxene and titanomagnetite of the baima fe ti oxide bearing layered mafic intrusion sw china are used to investigate fe isotopic fractionation during the formation of the fe ti oxide ore bodies and to constrain the origin of silicate minerals and fe ti oxides the baima intrusion comprises the lower zone of interlayered troctolite clinopyroxenite and oxide ores and the upper zone of gabbros significant differences of fe isotope values between olivine fe 56 0 01 to 0 11 clinopyroxene fe 56 0 11 to 0 22 and titanomagnetite fe 56 0 20 to 0 31 were observed in rocks and ores of the lower zone iron isotopic fractionation between olivine and clinopyroxene olivine and titanomagnetite and clinopyroxene and titanomagnetite exhibits large variations of 0 06 to 0 22 0 12 to 0 27 and 0 00 to 0 20 respectively suggesting disequilibrium fractionation this disequilibrium cannot be explained by thermal or chemical gradient induced kinetic fractionation or by possible subsolidus exsolution of granular ilmenite from titanomagnetite instead it could be attributed to crystallization of silicates and titanomagnetite from two immiscible si rich and fe rich liquids continuous segregation of the fe rich liquid changed the fe isotopic composition of the si rich liquid and thus the fe isotopic compositions of olivine and clinopyroxene crystallized from it resulting in disequilibrium fe isotopic fractionation between them the effect of oxygen fugacity on the crystallization order of titanomagnetite and ilmenite from the fe rich melts on the other hand gave rise to the disequilibrium fe isotope fractionation between titanomagnetite and olivine clinopyroxene

the magmatic hydrothermal transition in the lower oceanic crust clues from the ligurian ophiolites italy abstract the gabbroic bodies from the jurassic ligurian ophiolites are structurally and compositionally similar to the gabbroic sequences from the oceanic core complexes of the mid atlantic ridge initial cooling of the ligurian gabbros is associated with local development of hornblende bearing felsic dykes and hornblende vein networks the hornblende veining is correlated with the widespread development of hornblende as coronas pseudomorphs after the clinopyroxene in the host gabbros in addition the studied gabbroic body includes a mantle sliver locally containing hornblende gabbros and hornblendite veins the hornblendes from the felsic dykes and the hornblende rich rocks within the mantle sliver show a similar geochemical signature characterized by low mg cao and al2o3 negligible cl and high tio2 k2o ree y zr and nb concentrations the whole rock sm nd isotopic compositions of the felsic dykes and the hornblende rich rocks define a sm nd isochron corresponding to an age of 154 20 ma and an initial end of 9 2 0 5 the 18o of the hornblendes and coexisting zircons from these rocks about 4 5 and 5 8 respectively do not indicate the presence of a seawater component in these melts the formation of the felsic dykes and of the hornblende rich rocks within the mantle sliver involved sio2 rich silicate melts with negligible seawater component which presumably were derived from high degree fractional crystallization of mor type basalts the vein and the coronitic pseudomorphic hornblendes show high mg and cao significant cl 0 02 0 17 wt and low tio2 and k2o concentrations the coronitic pseudomorphic hornblendes have trace element compositions similar to those of the clinopyroxenes from the gabbros and 18o values 1 0 to 0 7 close to seawater suggesting an origin by reaction between migrating seawater derived fluids and the host gabbros the vein hornblendes commonly show slight lree enrichment relatively high concentrations of nb up to 2 5 ppm and 18o ranging from 3 7 to 0 8 the crystallization of these hornblendes most likely involved both seawater and magmatic components

two tiered magmatic hydrothermal and skarn origin of magnetite from gol gohar iron ore deposit of se iran in situ la icp ms analyses abstract genesis of magnetite from gol gohar iron deposit ggid of southeastern iran is studied with reference to elemental composition more than 1 2 billion tonnes of magnetite ore at 58 total fe is hosted by greenschist to amphibolite facies metapelites and magnesian marbles the ggid occurs in the mainly metamorphic terrain of sanandaj sirjan geological province with continental margin tectonic setting the magnetite bearing ore is divided into two distinct types of massive and banded the latter hosted mainly by magnesian marbles both subtypes of the ore bodies are associated with mineral assemblages consisting of calcite dolomite forsterite tremolite actinolite talc serpentine and chlorite the ore minerals in both subtypes are magnetite hematite with minor amounts of pyrite pyrrhotite and chalcopyrite concentrations of temperature dependent elements ti al and ga in the two subtypes would suggest that temperature of formation was higher for the massive magnetite with ti 626 ppm al 69 ppm and ga 56 ppm on average and relatively lower for the banded magnetite with ti 60 ppm al 62 ppm and ga 4 ppm on average the multi element diagrams for massive magnetite show patterns closer to those of magmatic hydrothermel iron deposits kiruna type whereas patterns of the banded magnetite match better with those of skarn deposits particularly the magnesian skarns average concentrations of v 1000 ppm and cr 4 ppm of the massive subtype fall within the range of those of kiruna type deposits and the in average lower concentrations of v 10 ppm and cr 1 ppm of the banded magnetite match the values of skarn deposits the average v content of the massive magnetite 1342 ppm is consistent with the global range of magmatic hydrothermal magnetite up to 3880 ppm but different from global values of purely magmatic magnetites up to 6600 ppm the banded magnetites contain 0 21 25 ppm v which is only consistent with the lowest values of hydrothermal magnetites we contend that the massive magnetite was formed by magmatic hydrothermal processes i e kiruna type and the banded magnetites were generated via metasomatic reactions between iron rich residual magmatic fluids and the magnesian carbonate host rocks i e skarn type

transient pressure analysis of fractured well in bi zonal gas reservoirs for hydraulic fractured well how to evaluate the properties of fracture and formation are always tough jobs and it is very complex to use the conventional method to do that especially for partially penetrating fractured well although the source function is a very powerful tool to analyze the transient pressure for complex structure well the corresponding reports on gas reservoir are rare in this paper the continuous point source functions in anisotropic reservoirs are derived on the basis of source function theory laplace transform method and duhamel principle application of construction method the continuous point source functions in bi zonal gas reservoir with closed upper and lower boundaries are obtained sequentially the physical models and transient pressure solutions are developed for fully and partially penetrating fractured vertical wells in this reservoir type curves of dimensionless pseudo pressure and its derivative as function of dimensionless time are plotted as well by numerical inversion algorithm and the flow periods and sensitive factors are also analyzed the source functions and solutions of fractured well have both theoretical and practical application in well test interpretation for such gas reservoirs especial for the well with stimulated reservoir volume around the well in unconventional gas reservoir by massive hydraulic fracturing which always can be described with the composite model

kiglapait mineralogy iii olivine compositions and rayleigh fractionation models olivints present throughout the layered cumulates of the kiglapait intrusion record extreme iron enrichment during fractional crystallization mn is less compatible than fe the exchange coefficient kd for mn fe ol liq has values near 0 95 but they drop to 0 7 near the lower one upper one boundary ca is depleted by more than a factor of 30 relative to experimental values at 5 kbar pressure attempts to find a sink for ca in the lower zone without invoking liquid as a reactant are unconvincing and questions of metastability arise cumulus olivines vary systematically to lower fo contents with stratigraphic height using equilibrium values for the exchange coefficient kd fe mg ol ljq j and the observed mode of olivine and residual porosity a rayleigh fractionation calculation reproduces the observed lower zone trend without recourse to multiple injections of magma an anomalously fe rich region above the main ore band in the upper zone ascribed to ponding of fe rich magma at the floor of the intrusion until later buoyant residual magma entrained the fe rich residua such fe rich ponds probably account for the abnormal fe enrichment shown by some other fenner trend layered intrusions summation over the observed crystal compositions yields values of xjug that do not represent the equilibrium liquid but that reduce to it by a simple multiplier p 0 78 this result means that if ko is known the high temperature liquidus olivine compositions can be retrieved or vice versa because the observed olivine compositions are supported by realistic forward models there is no need to invoke evolved boundary layer liquids to explain the in situ crystallization of kiglapait cumulates classical cumulate theory suffices

response of a partially penetrating well in a heterogeneous aquifer integrated well face flux vs uniform well face flux boundary conditions a two dimensional integrated well face flux iwff model is developed for computing the drawdown at the well face and around a fully or partially penetrating well with wellbore storage situated in a layered confined aquifer in this model we calculate drawdown and well face flux distributions by numerically solving a two dimensional diffusion equation in cylindrical coordinates subject to appropriate initial and boundary conditions and to the well face boundary constraint of an integrated well face flux rather than the physically inconsistent uniform well face flux boundary condition the uwff model the differences between the iwff and uwff models in a partially penetrating well situated in a homogeneous isotropic aquifer are insignificant for wellbore drawdown less than 3 but are pronounced for the well face flux in fact the latter strongly deviates from uniformity as the ratio of the screen length to the aquifer thickness decreases for partially penetrating wells situated in multilayer aquifers significant differences between the two models may arise especially if the screen is not located in the most conductive layer these differences depend on the hydraulic conductivity contrast of the adjacent layers consequently the uniform well face flux boundary condition should be used with extreme caution

petrogenesis and tectonic implications of the iron rich tholeiitic basalts in the hutuo group of the wutai mountains central trans north china orogen abstract the hutuo group located in the wutai mountains area is characteristic of paleoproterozoic strata in the north china craton and plays an important role in establishing evolutionary processes in the trans north china orogen we present petrological observations along with geochemical and nd isotopic data for basalts in the qingshicun and hebiancun formations of the hutuo group these basalts are enriched in tfeo 11 97 18 01 wt consistent with occurrences of iron rich basalt world wide they also display relatively high mgo 4 95 12 25 wt ni 79 121 ppm and cr 37 101 ppm and low in sio 2 41 37 51 95 wt therefore the iron rich character of the hutuo group basalts originated with their parental magma rather than via shallow crustal fractionation at low oxygen fugacity as inferred for many high iron basalts the hutuo group basalts exhibit weak to moderate differentiation of light ree over heavy ree la lu cn 2 61 6 79 with minor or slight eu anomalies eu eu 0 77 1 41 and also show the nb and ti troughs without obvious zr and hf anomalies the nd t values of the basalts range from 1 23 to 0 81 with t dm of 2489 2664 ma the basalts most plausibly originated from the fertile subcontinental lithosphere mantle and in the case of the qingshicun formation basalts also underwent the crustal contamination basalts in the hutuo group also have the high zr hf ratios and present high ti v values of 24 55 and zr y ratios ranging from 4 6 to 13 6 suggesting that they were emplaced in a within plate setting considering the sedimentary associations and detrital fragments in the hutuo and gantaohe groups and bimodal magmatism along the trans north china orogen we propose that 2 2 2 0 ga geological events within the orogen were rift related but did not result from subduction or island arc processes

silica rich lavas in the oceanic crust experimental evidence for fractional crystallization under low water activity we experimentally investigated phase relations and phase compositions as well as the influence of water activity ah2o and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium depleted system at shallow pressure 200 mpa moreover we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment sio2 74 6 wt as starting material we used a dacitic glass dredged at the pacific antarctic rise phase assemblages in natural high silica systems reported from different locations of fast spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt water content t 950 c melt h2o 1 5 wt at redox conditions slightly below the quartz fayalite magnetite buffer the relatively low water content is remarkable because distinct hydrothermal influence is generally regarded as key for producing silica rich rocks in an oceanic environment however our conclusion is also supported by mineral and melt chemistry of natural evolved rocks these rocks are only congruent to the composition of those experimental phases that are produced under low ah2o low feo contents under water saturated conditions and the characteristic enrichment of al2o3 in high ah2o experiments in particular contradict natural observations while experiments with low ah2o match the natural trend moreover the observation that highly evolved experimental melts remain h2o poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination

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

the formation of sio2 rich melts within the deep oceanic crust by hydrous partial melting of gabbros small amounts of felsic evolved plutonic rocks often called oceanic plagiogranites always occur as veins or small stocks within the gabbroic section of the oceanic crust four major models are under debate to explain the formation of these rocks 1 late stage differentiation of a parental morb melt 2 partial melting of gabbroic rocks 3 immiscibility in an evolved tholeiitic liquid and 4 assimilation and partial melting of previously altered dikes recent experimental data in hydrous morb type systems are used to evaluate the petrogenesis of oceanic plagiogranites within the deep oceanic crust experiments show that tio2 is a key parameter for the discrimination between different processes tio2 is relatively low in melts generated by anatexis of gabbros which is a consequence of the low tio2 contents of the protolith due to the depleted nature of typical cumulate gabbros formed in the oceanic crust on the other hand tio2 is relatively high in those melts generated by morb differentiation or liquid immiscibility since the tio2 content of many oceanic plagiogranites is far below that expected in case of a generation by simple morb differentiation or immiscibility these rocks may be regarded as products of anatexis this may indicate that partial melting processes triggered by water rich fluids are more common in the deep oceanic crust than believed up to now at slow spreading ridges seawater may be transported via high temperature shear zones deeply into the crust and thus made available for melting processes

thermodynamic analysis of fe and mg partitioning between plagioclase and silicate liquid thermodynamic analysis of fe and mg bearing plagioclase and silicate liquid was carried out based on reported element partitioning data between plagioclase and silicate liquid in reduced conditions solution properties of ternary feldspar standard state properties of plagioclase endmembers and solution properties of multicomponent silicate liquid derived mixing properties of fe and mg bearing plagioclase are in harmony with estimated results from synthetic experiments in the systems caal2si2o8 cafesi3o8 and caal2si2o8 camgsi3o8 based on the determined solution properties of the plagioclase a computer program to calculate the element partition relationships between fe and mg bearing plagioclase and multicomponent silicate liquid was developed the feo mgo and mgo mgo feo in plagioclase predicted from known liquid compositions and pressure are in agreement with measurements within 0 2 wt 0 1 wt and 0 1 mol ratio respectively the fe3 content in plagioclase crystallized at high oxygen fugacity can be estimated with this program the fe3 total fe ratio in plagioclase crystallized near the quartz fayalite magnetite buffer ranges from 0 to 0 5 which is consistent with previous study on natural plagioclase in submarine basalt derived solution properties of the fe and mg bearing plagioclase are also used to calculate equilibrium composition relationship between olivine and plagioclase change of xfo in olivine coexisting with plagioclase affects mgo and feo contents in plagioclase greatly the present model predicts xfo of coexisting olivine from the chemical composition of plagioclase to 0 1 accuracy at given pressure and temperature

two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton petrogenesis and tectonic implications abstract mafic dyke swarms constitute a common occurrence within the cratonic provinces in the world since the archean proterozoic boundary and their geneses harbor critical information for facilitating regional tectonic and supercontinental reconstruction this zircon u pb dating and geochemical study documents two episodes of paleoproterozoic mafic intrusions from liaoning province north china craton ncc the haicheng suite hcs with an emplacement age of ca 2125 ma from the liaodong peninsula and the guohua suite ghs with an age of ca 1816 ma from the western liaoning terrane the hcs meta gabbros are tholeiitic in composition with an sio 2 range from 46 to 52 modest enrichment in light rare earth elements lree and depletion in high field strength elements hfse and possess radiogenic whole rock nd nd t 1 91 to 4 21 and zircon hf hf t 4 02 to 8 48 isotopic compositions these features endow the hcs with a juvenile subduction fluid metasomatized lithospheric mantle source by contrast the ghs exhibits a meta gabbroic to dioritic composition and a transitional character from tholeiitic to calc alkali with variably enriched lrees and more evolved isotopic signatures nd t 0 20 to 5 82 zircon hf t 0 09 to 4 91 than the hcs while the relatively intact high fe gabbroic samples are supposed to represent partial melts from a fertile cratonic sub continental lithospheric mantle source in the garnet spinel stability field the low fe dioritic ones tend to bear the imprints of subsequent assimilation and fractional crystallization process apart from making an important contribution to the present archive of the paleoproterozoic mafic dyke swarms in the ncc the present two mafic magmatic suites witnessed a shift in tectonic setting from a subduction related continental arc environment to a post orogenic extensional regime synthesizing two suites with coeval felsic igneous episodes as well as concomitant episodic metamorphic events in the jiao liao ji belt leads to the characterization of a possible divergent double subduction system in the eastern ncc during the time span of ca 2 2 1 80 ga synchronized beating of episodic magmatic and metamorphic pulses in the constituent mobile belts of the ncc carries further implication of attesting to the ubiquity and importance of divergent double subduction system in the cratonic amalgamation and its incorporation within the supercontinent columbia

platinum group element distribution in the main zone and upper zone of the bushveld complex south africa abstract the platinum group element pge contents of the upper portions of the bushveld complex were investigated with three questions in mind a in natural systems does magnetite concentrate os ir ru and rh ipge as has been observed in experimental systems b is there a au pd enriched layer present such as observed in the upper parts of the skaergaard intrusion c can changes in metal ratios be used for prospecting for pge deposits in the sulfide poor main magnetite layer of the eastern bushveld ir and rh are enriched relative to pt pd and au and this could be because magnetite preferentially concentrated ir and rh over pt pd and au however in most other magnetite layers no enrichment was observed this could be because most magnetite layers contain approximately 1 sulfides and the pge budget is dominated by the sulfides these sulfides obscured the effects of magnetite collecting ipge because sulfides collect all the pge and the partition coefficients for the pge into a sulfide liquid are much greater than the partition coefficient for ipge into magnetite the weighted average of the platinum group elements pge and au over the 2000 m of sampled stratigraphy is au 2 1 ppb pd 1 7 ppb pt 1 7 ppb rh 0 18 ppb ru comparison of the composition of the marginal rocks of the bushveld with a weighted average for the complete 6 km of the bushveld cumulates shows that the cumulate pile is much richer in compatible elements ir rh cr and poorer in incompatible elements sm and hf than the marginal rocks two possible solutions to this are a the magma emplaced into the chamber was a crystal mush and thus more mafic than marginal rocks to the intrusion or b fractionated magma has been removed from the cumulate sequence and either irrupted or intruded the country rocks as granites and granophyres

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

the formation of p rich fe ti oxide ore layers in the taihe layered intrusion sw china implications for magma plumbing system process abstract the taihe intrusion is one of the layered intrusions that host giant fe ti oxide deposit in the central part of the emeishan large igneous province sw china different from the other layered intrusions the taihe intrusion has a massive fe ti oxide ore layer at the top of the lower zone lz particularly the rocks of both middle and upper zones contain as much as 5 12 apatite and the most important fe ti oxide ore layers apatite magnetite clinopyroxenite occur at the bases of cyclic units in the middle zone mz rather than in the lower zone lz high cr and ni concentrations of clinopyroxene 65 263 ppm and 66 83 ppm respectively and high an contents of plagioclase 79 80 of the lz rocks indicate their more primitive parental magmas the clinopyroxene and plagioclase of the mz rocks are characterized by low cr and ni contents 1 21 ppm and 0 4 10 ppm respectively and low an 51 67 indicating more evolved parental magma the fe ti oxide ore layers in the mz are not only high in fe and ti but also enriched in p2o5 and rare earth elements indicating an unusual fe ti p rich parental magma it is speculated that the mz represents a later intrusion of fe ti p rich magmas that were produced by the fe ti enriched magma from a deep seated magma chamber mixing with the extensively evolved p rich magma in a middle level magma chamber early crystallization and cumulation of fe ti oxide and apatite together with clinopyroxene from the fe ti p rich magmas from the middle level magma chamber resulted in the formation of fe ti oxide ore layers in the mz fe ti p rich magma and apatite magnetite clinopyroxenites occur in the base of cyclic units whereas apatite gabbros are presented at the upper parts of each cyclic unit the upper zone uz is the product of the crystallization of highly differentiated magma consists chiefly of apatite gabbro and minor intercalated apatite clinopyroxenite

precious metal enrichment at low redox in terrestrial native fe bearing basalts investigated using laser ablation icp ms primary native fe is a rare crystallizing phase from terrestrial basaltic magmas requiring highly reducing conditions fo2 iron wustite buffer in order to form reducing conditions in basaltic magmas can be achieved through assimilation of carbonaceous crustal material which leads to formation of an immiscible molten c rich native fe alloy liquid if this liquid also contains sufficient sulfur it can undergo further division into conjugate fe c rich and a fe s rich immiscible melts that can effectively scavenge the highly siderophile elements hse re au and the platinum group elements pge pd pt rh ru ir os as well as ni and cu to economic abundances three localities are known globally where native fe bearing mafic rocks occur 1 paleocene basalts of disko island west greenland 2 a miocene lava of the buhl basalts germany and 3 mafic intrusions associated with the late permian siberian flood basalts in this contribution we report major and minor element compositions and hse concentrations for the main alloy phases feni metal and cohenite and sulfide for all three known global occurrences of native fe bearing basalt total hse abundances in metal grains obtained by laser ablation inductively coupled plasma mass spectrometry la icp ms are lowest in the buhl basalt 0 05 ppm intermediate in the disko island basalts 4 8 ppm and highest the siberian khungtukun and dzhaltul intrusions 10 30 ppm these differences demonstrate that while native fe formation is the result of carbonaceous crustal assimilation hse enrichment is not ubiquitous during this process the siberian occurrences are characterized by pt pge ppge pt pd enrichment relative to the ir pge ipge rh ru ir os consistent with models of early stage fractionation of olivine chromite and metallic ipge in staging magma reservoirs prior to the addition of c rich crustal materials in the shallow crust relative to noril sk ni cu pge sulfide ores the siberian native fe basalts are enriched in the ppge relative to the ipge but exhibit ru enrichments in contrast disko island native fe rocks do not show significant fractionation of the ppge from the ipge but have positive re and ru anomalies and high os ir ratios to reconcile these observations we present a general model where some parental melts experienced early stage crustal assimilation in staging magma reservoirs prior to reduction by carbon rich materials e g khungtukun dzhaltul whereas basaltic parental melts to disko island and buhl solely experienced interaction with carbonaceous material resulting in extensive devolatilization native fe segregation and native fe formation

radial flow to a partially penetrating well with storage in an anisotropic confined aquifer summary drawdowns generated by extracting water from large diameter e g water supply well are affected by wellbore storage we present an analytical solution in laplace transformed space for drawdown in a uniform anisotropic aquifer caused by withdrawing water at a constant rate from partially penetrating well with storage the solution is back transformed into the time domain numerically when the pumping well is fully penetrating our solution reduces to that of papadopulos and cooper 1967 hantush 1964 when the pumping well has no wellbore storage theis 1935 when both conditions are fulfilled and yang 2006 when the pumping well is partially penetrating has finite radius but lacks storage newly developed solution is then used to explore graphically the effects of partial penetration wellbore storage and anisotropy on time evolutions of drawdown in the pumping well and in observation wells we concluded after validating the developed analytical solution using synthetic pumping test

chondritic models of 4 vesta implications for geochemical and geophysical properties simple mass balance and thermodynamic constraints are used to illustrate the potential geochemical and geophysical diversity of a fully differentiated vesta sized parent body with a eucrite crust e g core size and density crustal thickness the results of this analysis are then combined with data from the howardite eucrite diogenite hed meteorites and the dawn mission to constrain vesta s bulk composition twelve chondritic compositions are considered comprising seven carbonaceous three ordinary and two enstatite chondrite groups our analysis excludes ci and ll compositions as plausible vesta analogs as these are predicted to have a negative metal fraction second the melts thermodynamic calculator is used to show that the enstatite chondrites the cv ck and l groups cannot produce juvinas like liquids and that even for the other groups depletion in sodium is necessary to produce liquids of appropriate silica content this conclusion is consistent with the documented volatile poor nature of eucrites furthermore carbonaceous chondrites are predicted to have a mantle too rich in olivine to produce typical howardites and to have fe mn ratios generally well in excess of those of the heds on the other hand an na depleted h chondrite bulk composition is capable of producing juvinas like liquids has a mantle rich enough in pyroxene to produce abundant howardite diogenite and has a fe mn ratio compatible with eucrites in addition its predicted bulk silicate density is within 100 kg m 3 of solutions constrained by data of the dawn mission however oxidation state and oxygen isotopes are not perfectly reproduced and it is deduced that bulk vesta may contain approximately 25 of a cm like component values for the bulk silicate composition of vesta and a preliminary phase diagram are proposed

on the aquitard aquifer interface flow and the drawdown sensitivity with a partially penetrating pumping well in an anisotropic leaky confined aquifer summary a mathematical model for describing groundwater flow to a partially penetrating pumping well of a finite diameter in an anisotropic leaky confined aquifer is developed the model accounts for the jointed effects of aquitard storage aquifer anisotropy and wellbore storage by treating the aquitard leakage as a boundary condition at the aquitard aquifer interface rather than a volumetric source sink term in the governing equation which has never developed before a new semi analytical solution for the model is obtained by the laplace transform in conjunction with separation of variables specific attention was paid on the flow across the aquitard aquifer interface which is of concern if aquitard and aquifer have different pore water chemistry moreover laplace domain and steady state solutions are obtained to calculate the rate and volume of total leakage through the aquitard aquifer interface due to pump in a partially penetrating well which is also useful for engineers to manager water resources the sensitivity analyses for the drawdown illustrate that the drawdown is most sensitive to the well partial penetration it is apparently sensitive to the aquifer anisotropic ratio over the entire time of pumping it is moderately sensitive to the aquitard aquifer specific storage ratio at the intermediate times only it is moderately sensitive to the aquitard aquifer vertical hydraulic conductivity ratio and the aquitard aquifer thickness ratio with the identical influence at late times

in situ la icp ms trace elemental analyses of magnetite the late palaeoproterozoic sokoman iron formation in the labrador trough canada abstract the sokoman iron formation in the labrador trough canada a typical granular iron formation gif is coeval with the 1 88 ga nimish volcanic suites in the same region it is composed of the lower middle and upper iron formations in addition to primary and altered magnetite in iron formations of the hayot lake rainy lake and wishart lake areas magnetite in volcanic breccia associated with the iron formation is identified for the first time in the stratigraphy trace elemental compositions of the most primary altered and volcanic brecciated magnetite of the sokoman iron formation were obtained by la icp ms commonly detected trace elements of magnetite include ti al mg mn v cr co and zn these three types of magnetite have different trace elemental compositions primary magnetite in the iron formation has a relatively narrow range of compositions with the depletion of ti pb mg and al magnetite from volcanic breccia is rich in ti al v mn mg zn cu and pb indicative of crystallization from mantle derived magmas altered magnetite in the iron formation shows a relatively wide range of trace elemental compositions mineralizing fluids associated with magmas that generated the 1 88 ga nimish volcanic suites circulated through the sedimentary piles to further enrich the iron formations and to form magnetite with variable compositions the comparisons of different types of primary and altered magnetite in the iron formation in the region show distinct provenance discrimination our findings also support the origin of iron formations in association with multiple stages of exhalative volcanic and hydrothermal processes

stable and metastable silicate liquid immiscibility in ferrobasalts the onset of immiscibility in ferrobasaltic systems has been the subject of much research recently the compositional space of the two liquid field and the maximum temperature of the binodal surface have been investigated experimentally but results from static and centrifuge experiments are controversial in the article by hou and veksler 2015 may june issue entitled experimental confirmation of high temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems the authors present experimental evidence for immiscibility between silica and iron rich melts at 1150 1200 c which are significantly higher to previous studies ca 1000 1025 c these results have important implications for potential large scale differentiation of magmas by liquid unmixing and for the formation of both fe ti p rich melts and rhyolites

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage