prolonged magmatism juvenile nature and tectonic evolution of the chinese altai nw china evidence from zircon u pb and hf isotopic study of paleozoic granitoids abstract paleozoic granitoid magmatism played an important role in the tectonic evolution of the chinese altai and zircon u pb and hf isotopic compositions have been determined for samples from eleven granitic plutons batholiths the jiadengyu gneissic granitic pluton yielded a zircon u pb age of 479 ma and thus it does not represent precambrian basement as suggested previously our results and published data demonstrate that voluminous granitoids were continuously emplaced over more than 30 area of the chinese altai during the period from 447 ma to 368 ma with a climax at ca 400 ma ages for zircon overgrowth rims demonstrate additional thermal events at ca 360 and 280 ma respectively positive e hf t values 0 to 9 of normal magmatic zircons suggest that the granitoid magmas were derived from juvenile sources xenocrystic zircon cores are 543 421 ma old and also give positive e hf t values 2 5 to 12 suggesting their origin as early crystallized minerals in the magma chambers or as inherited cores from newly accreted meterials the strong magmatism at ca 400 ma significantly changed the hf isotopic composition of the magma source by substantial input of juvenile material in a relatively short period geophysical geological and geochemical data support that ridge subduction was a possible mechanism for the strong magmatism ca 400 ma and the above mentioned change of hf isotopic composition in the magma source

chemistry of rainwater in the massif central france a strontium isotope and major element study atmospheric aerosols sea salt crustal dust and biogenic aerosols are the primary source of dissolved species in rainwater as well as one of the sources of dissolved species in river water chemical weathering studies require quantification of this atmospheric input the crustal component of atmospheric input can have various origins both distant and local the proportions of the various inputs marine distant or local are determined in this study strontium isotope ratios and ca na k mg al cl so4 no3 and sr concentrations were measured in rainwater samples collected in the massif central france over a period of one year each sample collected automatically represents a monthly series of rain events chemical composition of the rainwater samples varied considerably and the 87sr 86sr ratios ranged between 0 709198 and 0 713143 using na as an indicator of marine origin and al for the crustal input in rain samples the proportion of marine and crustal elements was estimated from elemental ratios a marine origin of 4 to 100 of cl of 0 6 to 20 of the so4 of 1 to 10 of ca 1 to 40 of k 4 to 100 of mg and 1 to 44 of sr was determined strontium isotopes were used to characterize the crustal sources the 87sr 86sr ratios of the crustal sources varied considerably from 0 7092 to 0 71625 and indicate the occurrence of multiple sources for the crustal component in the analysed rainwaters

hydrothermal evolution and ore genesis of the hongshi copper deposit in the east tianshan orogenic belt xinjiang nw china constraints from ore geology fluid inclusion geochemistry and h o s he ar isotopes abstract the hongshi lode type copper deposit is located in the kalatag region in the east tianshan xinjiang nw china the lode ore bodies are hosted in the late ordovician to early silurian daliugou formation and the cu mineralization is closely associated with andesite minor amounts of intrusive rocks such as the quartz porphyry are also exposed the country rocks have undergone extensive silicification chlorite alteration and sericite alteration the metallic minerals are pyrite and chalcopyrite with minor magnetite sphalerite and galena the gangue minerals are quartz sericite epidote calcite and chlorite the mineralized veins in the hongshi deposit can be divided into an early quartz pyrite vein stage the main quartz chalcopyrite pyrite sphalerite vein stage and a late quartz calcite chlorite vein stage fluid inclusion petrography shows that two phase liquid rich type i two phase vapor rich type ii and daughter bearing multiphase type iii fluid inclusions are present in the hydrothermal quartz sulfide veins in the hongshi deposit the fluid inclusions in the early stage minerals are mainly type i and type ii with minor type iii their homogenization temperatures and salinities range from 198 c to 315 c with a peak value of 253 c and from 1 40 to 8 81 wt nacl equiv respectively the coexistence of type ii and type iii inclusions and their similar homogenization temperatures but contrasting salinities suggest that fluid boiling processes occurred in the early stage the main stage minerals feature dominantly type i and type ii inclusions with homogenization temperatures and salinities of 168 c 280 c with a peak value of 209 c and 1 40 6 16 wt nacl equiv respectively the late stage minerals feature dominantly type i and type ii inclusions with homogenization temperatures and salinities of 109 c 179 c with a peak value of 157 c and 0 53 3 23 wt nacl equiv respectively the initial ore forming fluids of the hongshi deposit were therefore associated with an h2o nacl system with a near neutral ph low intermediate temperatures and low salinities the oxygen and hydrogen stable isotopic analyses of fis in quartz from the different ore forming stages show that the ore forming fluids were of volcanic origin with gradually increasing proportions of meteoric water during after mineralization the 34s values of chalcopyrite and pyrite from the main ore forming stage vary between 1 9 and 11 9 suggesting a volcanic source the 3he 4he ratios of fluid inclusions in the main stage pyrite mainly range from 0 12 to 1 40 ra and the 40ar 36ar values vary from 310 to 337 all these isotopic characteristics suggest that the ore fluids were likely derived from a combination of crustal and mantle components combining the integrated analysis of ore deposit geology the fluid evolutionary process and h o s he ar isotopes we suggest that the hongshi deposit should be classified as a volcanic subvolcanic hydrothermal copper deposit processes including local fluid unmixing decreasing temperature and fluid mixing may have been responsible for the hydrothermal alteration and cu precipitation

re os and u pb geochronology for the xiaorequanzi vms deposit in the eastern tianshan nw china constraints on the timing of mineralization and stratigraphy abstract the xiaoriquanzi volcanogenic massive sulfide vms cu zn deposit occurs at the western part of the paleozoic dananhu haerlik arc in the eastern tianshan xinjiang china due to a lack of precise mineralization ages the metallogenesis of the deposit has long been debated in this study systematic geochronological methods are used to constrain the mineralization age of the deposit the deposit is hosted in the xiaorequanzi formation volcanic sedimentary rocks the orebodies occur as clusters of lenticular bodies with or without banding and they are controlled by the nw trending acticline the ore types contain massive banded laminated and chlorite enriched ores as well as vein type veinlet dissemination and dissemination ores in this study re os dating of the chalcopyrite from the xiaorequanzi deposit yields an isochron age of 354 11 ma and initial 187os 188os ratios of 0 39 0 14 which is consistent with the zircon u pb ages of ore hosted tuff sandstone and dacite at 357 3 2 4 ma and 359 5 3 4 ma respectively zircon u pb dating reveals that the mineralized granite porphyry formed at 354 7 3 2 ma and this age is similar to the exhalative syn sedimentary mineralization age 354 11 ma thus precise geochronologic studies reveal that the seafloor volcanic hydrothermal system formed exhalative syn sedimentary mineralization in the local extensional basin of the dananhu haerlik arc during the early carboniferous 354 357 ma from early silurian to carboniferous two epochs vms and porphyry deposits alternately formed in dananhu haerlik long lived arc this reveals complicated arcs basins tectonic transformation at the island arc setting

isotopic identification of gases of a deep origin in french thermomineral waters within the subsurface convective system which constitutes the thermomineral waters of which the meteoric origin is proved by the oxygen deuterium couple the associated gases free or dissolved may represent the only juvenile component in this cycle the juvenile origin of the gases can be clearly established through ascertaining the isotopic composition of certain elements argon nitrogen carbon and helium the study of these gases associated with thermomineral waters has been undertaken systematically since 1976 one of the first objectives of these investigations has been the determination of the carbon isotopic compositions of the carbon dioxide bicarbonate system for 50 thermomineral springs in various geological settings the massif central pyrenees and vosges mountainous regions france on the basis of isotopic compositions three sources of primordial or initial carbon have been put forward which correspond to characteristic figures for the carbon compositions expressed in 13c values the exogenous carbon domain 13cco2 from 10 to 25 13chco 3 from 18 to 2 the endogenous magmatic carbon domain 13cco2 from 10 to 2 13chco 3 from 2 to 6 and the endogenous sedimentary carbon domain 13cco2 from 2 to 2 and 13chco 3 6 in the case of springs with exogenous carbon of which a part is atmospheric nitrogen isotopes confirm that origin in the cases of springs with magmatic or mantle carbon argon isotopes indicate also a deep origin

tracing surface water mixing and groundwater inputs using chemical and isotope fingerprints δ18o δ2h 87sr 86sr at basin scale the loire river france abstract the spatial and temporal distributions of major elements stable isotopes of water molecule and strontium isotope ratios were investigated in the surface waters of the loire river basin the present study using a coupled hydrological and geochemical approach focuses on surface water mixing and the interactions between ground and surface water stable isotopes 18o 2h provide good evidence for the complex hydrological behavior of the loire river system at the basin scale and if binary mixing of surface water masses explain the longitudinal evolution of the loire signature in the upstream part of the basin groundwater contributions are required to explain locally the loire signature the water chemistry in the different zones of the basin shows large variations in major element contents the no3 content in the loire river roughly increases from up to downstream and is mainly controlled by the input from tributaries the highest concentrations are observed in the middle part of the loire basin in close relation with the diffuse agricultural sources in terms of water rock interaction using na as the reference element the loire basin data are scattered between the three main end members representing the major lithologies i e basalts granite gneiss and carbonate strontium isotope ratios measured in water range from 0 70691 to 0 71395 and plotted vs the ca na ratios the 87sr 86sr ratios clearly discriminate the three main lithological endmembers in the middle loire section the loire flow rate increases without significant inputs of surface water previous studies attributed this increase to groundwater inputs the relationship between 87sr 86sr and the cl sr ratios clearly shows the groundwater inputs from the beauce carbonate aquifer along a 90 km river profile between orleans and amboise these conservative tracers can be used to calculate up to 20 groundwater mixing during low flow period

surface water groundwater interactions in an alluvial plain chemical and isotopic systematics our work on the loire river forms part of a french national research program dedicated to wetlands and aims to better understand the global functioning of the system from the hydrological geochemical ecological and sociological aspects the present study using a coupled hydrological and geochemical stable and sr isotopes approach focuses on the soulangy site with its secondary anastomosing channels just below the confluence of the loire and allier rivers and also on the dorna nt site with two unconnected oxbow lakes 50 km upstream of the confluence the stable isotopes of water 18o 2h show that the alluvial or riverbank aquifer feeds the loire river during the summer but is not recharged by the river during flood periods in the winter the alluvial groundwater thus has a purely local origin from precipitation the major elements reveal an anthropogenic input of cl and more importantly of no3 especially near farms the 87sr 86sr isotopes identify different groundwater layers in the alluvium i e an upper and a lower alluvial aquifer and a perched aquifer at dornant that have relatively complex relationships with the surface water the two main rivers loire and allier present distinct geochemical characteristics reflecting the different lithologies that they drain upstream in addition the secondary channels lying parallel to the loire main stream at the soulangy site give different geochemical signatures which shows that they are not fed by the same overflows of the loire they are more or less well connected to the upper level of the alluvial plain and a longitudinal study of one of these channels has revealed a loire river influence progressively replaced by a water contribution from the upper alluvial aquifer similarly the two oxbow lakes at the dornant site are not supplied by the same water during the summer months a conceptual scheme of the loire hydrosystem based on 18o and 87sr 86sr suggests that the isotopic variations of the loire river can be related to a massif central surface water supply for the loire and allier main streams and to a groundwater supply from the alluvial plains

a synthesis of mineralization styles and geodynamic settings of the paleozoic and mesozoic metallic ore deposits in the altay mountains nw china abstract the altay mountains within the xinjiang region of northwestern china hosts major metallic ore deposits here we review the geological characteristics metallogenic features and tectonic settings of these deposits the metallic ore deposits in the altay mountains occur mainly within four regions north altay central altay south altay and erqis we recognize seven types of metallic ore deposits in the altay mountains vms submarine volcanogenic iron magmatic skarn pegmatite hydrothermal vein cu zn fe and orogenic gold among these types the vms pegmatite orogenic gold and skarn deposits are the most common most of the rare metal pegmatite deposits are distributed in central altay with only a few in south altay the vms submarine volcanogenic type iron and skarn type deposits are distributed in south altay whereas the orogenic type gold deposits are distributed in the erqis fault belt the hydrothermal vein type deposits occur in the erqis fault belt and chonghu er basin in south altay magmatic type deposits are mostly in the erqis fault belt and central altay based on isotopic age data the vms submarine volcanogenic type fe and skarn type cu pb zn fe mineralization occurred during early middle devonian 410 377 ma orogenic type au magmatic type cu ni and a small number of skarn type fe hydrothermal vein type cu zn pegmatite type rare metal deposits in early middle permian 293 261 ma pegmatite type rare metal deposits few skarn type fe deposit in early middle triassic 248 232 ma and dominantly represented by pegmatite type rare metal deposits in late triassic early jurassic 223 180 ma the metallic ore deposits in the altay mountains formed in various tectonic settings such as the early middle devonian continental arc and oceanic island arc early middle permian post collisional extensional setting and triassic early jurassic intracontinental setting

long term behaviour of continental hydrothermal systems u series study of hydrothermal carbonates from the french massif central allier valley abstract u series dating of hydrothermal carbonates deposited by co2 rich thermo mineral waters of the french massif central provides new insights on the long term behaviour of a continental hydrothermal system dating of aragonite veins and travertines impregnating old terrace levels of the allier river allowed identification of the main episodes of surface deposition and thus factors likely to influence these circulations fifteen layers from three veins and four travertines from two separate areas were analysed sr isotope compositions were also measured on vein samples the results show that this region was subjected to at least 3 main episodes of surface or near surface hydrothermal deposition 253 to 208 ky 135 to 100 ky and less than 8 ky comparison of these ages with a global climatic curve indicates that preferential deposition of carbonates occurs during warm periods suggesting a strong influence of climatic conditions on the hydrothermal system it is suggested that this climatic influence does not necessarily imply the absence of carbonate deposition during cold and dry periods but rather that carbonate precipitation might occur at depth before the geothermal fluids reach the surface in addition the isotope compositions of fluids recorded by the 87sr 86sr and 234u 238u initial ratios in the aragonite veins from coudes remained remarkably constant over 250 ky ranging from 0 71360 to 0 71371 and from 3 10 to 3 39 respectively the two samples coming from saladis show a slightly higher 234u 238u initial ratio around 3 95 the constancy of these ratios over such a long period suggests a hydrothermal system in a near steady state with respect to water rock interaction we thus propose a possible model allowing a conservative steady state despite variations in the water recharge rates in response to the climatic variations the difference between 234u 238u initial ratios measured in the coudes and saladis systems suggests the existence of two separate reservoirs and constrains their lateral extension to a few km at most

neoproterozoic to paleozoic geology of the altai orogen nw china new zircon age data and tectonic evolution abstract we present a synthesis and a new account of the geological and tectonic history of the terranes of the chinese paleozoic altai orogen together with new single zircon ages for granitic and rhyodacitic rocks a central terrane consists of neoproterozoic to silurian amphibolite facies metasedimentary rocks and abundant devonian carboniferous granites the presence of precambrian basement is indicated by sinian fossils our xenocryst ages and published nd mean crustal residence ages of granites felsic arc type lavas on the southern margin of the terrane have a mean 207pb 206pb zircon age of 505 ma reflecting the time of arc volcanism and the presence of xenocysts with ages between 614 and 921 ma suggests derivation by intracrustal melting accordingly we suggest that a cambro ordovician continental magmatic arc was built on the southern margin of the central terrane by northward subduction a low grade ordovician andean type arc with a continental basement is situated above a normal fault on

late permian triassic metallogeny in the chinese altay orogen constraints from mica 40ar 39ar dating on ore deposits abstract the central asian orogenic belt caob constitutes the largest phanerozoic accretionary orogen on earth it extends over 5000 km and hosting numerous metal deposits the chinese altay orogen an important element of the caob hosts abundant devonian ca 410 370 ma deposits the 40 ar 39 ar dating of seven mica separates from the representative samples syngenetic with orogenic type mineralization is summarized to record a poorly studied permian to triassic metallogenic episode in the chinese altay orogen the kelan and maizi basins in the chinese altay orogen which likely represent an arc accretionary complex contain a series of polymetallic lode deposits hosted in low grade metamorphic volcano sedimentary rocks two muscovite and five biotite separates were obtained from the ore forming veins paragenetically associated with au bearing polymetallic sulfides in the keketale pb zn wulasigou cu tiemurt pb zn dadonggou pb zn and sarekuobu au deposits these separates yielded 40 ar 39 ar plateau ages ranging from 260 ma to 205 ma integration of these results with other published geological and geochronological data indicates that the au cu pb zn mineralization post dated the final caob assembly with fluid movement and mineralization possibly driven by regional metamorphism and deformation it is herein proposed for a metallogenic model that the metamorphic fluid migration following final assembly of the caob results into the formation of the deposits

mantle derived helium in two peruvian hydrothermal ore deposits strong differences exist between the helium isotopic compositions of mantle derived magmas1 8 axial vent hotspring fluids9 14 subduction related magmas15 20 and many associated hot springs21 24 and the atmospheric and crustal values fig 1 here we report helium isotope ratios for two late tertiary fossil hydrothermal systems responsible for precious metal base metal and tungsten mineralization and compare them to those of circum pacific hot spring emanations the 3he 4he ratios of inclusion fluids hosted by gangue and sulphide minerals from casapalca and pasto bueno peru all lie between two and three times the atmospheric value indicating the presence of a dilute component of mantle helium consistent with previously reported stable isotope evidence for the presence of magmatic fluids during mineralization25 27 although post trapping modification of the helium isotope composition is possible we suggest that these apparently low values represent the composition of helium inherited from contributing magmas as a tracer of magmatic fluids in hydrothermal systems helium isotopes are decoupled from the factors that govern other stable isotope signatures

parent material controlled subsoil weathering in a chronosequence the allier terraces limagne rift valley france abstract the chronosequence in the allier terraces is subject to erratic changes in parent material composition with time approximately 65 of the total variance in the basaltic elements content in the allier terrace sands can be explained by the combined effect of parent material and time related neoformation of clay in the subsoil it is shown that parent material composition as a function of transport distance strongly influences weathering rate in the allier terrace chronosequence in order to evaluate parent material controlled weathering effects a process model simulation was made based on an exponential decrease of mgo and neoformation of clay long term simulations with this model suggest that parent material controlled subsoil weathering is significant for sediments with easy weatherable fragments after prolonged weathering the role of parent material decreases and becomes untraceable in strongly weathered materials

genesis of the yandong porphyry cu deposit in eastern tianshan nw china evidence from geology fluid inclusions and isotope systematics abstract the yandong porphyry cu deposit 372 mt at 0 58 cu is located in the center of the eastern tianshan xinjiang nw china multiple stage hydrothermal activities have resulted in potassic chlorite sericite phyllic and propylitic alteration in this deposit the yandong deposit formed in four stages i e an early quartz magnetite pyrite stage i a quartz pyrite chalcopyrite stage ii a quartz chalcopyrite pyrite molybdenite stage iii and a late quartz carbonate stage iv three evolutionary episodes were observed by a detailed fluid inclusion study 1 early ore stage i fluids were trapped under two phase conditions as evidenced by the coexistence of vapor rich v type inclusions homogenization temperatures 410 494 c average salinity 2 2 wt nacl equiv liquid rich l type inclusions homogenization temperatures 311 430 c average salinity 9 5 wt nacl equiv and hypersaline h type inclusions trapped at 300 bars or a depth of approximately 1 km assuming lithostatic pressure conditions 2 main ore stage ii and iii fluid inclusions in quartz were also trapped under two phase conditions boiling as identified by the coexistence of v and l type fluid inclusions l type inclusions homogenized between 161 and 390 c average 270 c with salinities of 1 6 9 9 wt nacl equiv average 4 9 wt nacl equiv and a depth of 1 km 100 bars hydrostatic pressure conditions 3 late ore stage iv fluids are represented by inclusions in barren quartz carbonate veinlets characterized by homogenization temperatures ranging from 123 to 261 c average 179 c and salinities between 0 7 and 4 7 wt nacl equiv average 2 0 wt nacl equiv the initial hydrothermal fluids are characterized by high temperature high salinity and high oxygen fugacity belonging to a h 2 o nacl system hydrogen and oxygen isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and mixed with abundant meteoric waters in the quartz carbonate stage sulfur stable isotope suggests that the ore forming metals came primarily from the tonalite magma that sourced from the subducted oceanic slab involving some mantle peridotites during ascent the cu mineralization of the yandong porphyry deposit occurred at a shallow crustal level approximately 1 km and the fluid boiling or phase separation decrease of temperature as well as fluid rock interaction were likely important factors responsible for metal accumulation and deposition in the magmatic hydrothermal system

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

origin of the subduction related carboniferous intrusions associated with the yandong porphyry cu deposit in eastern tianshan nw china constraints from geology geochronology geochemistry and sr nd pb hf o isotopes the yandong porphyry cu deposit is located at the south margin of the dananhu tousuquan arc belt in eastern tianshan northwest china the cu ores comprise mainly disseminations and vein zones in the potassic and phyllic alteration zones and are predominantly hosted in diorite porphyry tonalite and quartz porphyry which intruded into carboniferous qi eshan group volcanic rocks the u pb ages indicate that four intrusions were emplaced between 338 6 2 9 and 326 1 2 6 ma five molybdenite samples yield re os model ages of 333 8 329 5 ma with a weighted average age of 331 8 2 1 ma fourteen pyrite samples have 206pb 204pb of 17 776 18 959 207pb 204pb of 15 410 15 534 and 208pb 204pb of 37 323 38 127 similar to the age corrected data of the yandong tonalite the tonalite shows adakite like characteristics e g high sr y ratios and low y contents and has positive end t and ehf t values and low zircon o isotopes 3 7 4 6 suggesting that the melt was derived from partial melting of a subducted oceanic slab followed by mantle peridotite interaction the diorite porphyry exhibits high mg and low sr y values slightly negative eu anomalies and positive ehf t values indicating a lithospheric mantle source the quartz porphyry with stronger negative eu anomalies less evolved ehf t values and low 18o values 4 7 5 5 was probably derived from mantle melts that experienced mixing with lower crustal materials melts or assimilation the new data suggest that the yandong intrusions formed in an arc setting as the tonalite is genetically linked to the cu mineralization subduction related slab melts must have played a key role in the formation of the yandong deposit

the western central asian orogenic belt a window to accretionary orogenesis and continental growth abstract the architecture of accretionary orogens is a key to understand continental growth here we present an overview of the orogenic components and their amalgamation in the western central asian orogenic belt caob the caob records the convergence and interactions among various types of orogenic components including the japan type mariana type and alaska aleutian type arc systems as well as the active marginal sequences of the siberia craton which incorporated wide accretionary complexes and accreted arcs and terranes during construction of the caob the kazakhstan arc chain was characterized by multiple subduction whereas the northern fringe of the tarim craton remained mostly as a passive margin the multiple convergence and accretions among these various orogenic components generated huge orogenic collages in the late paleozoic and even in the early triassic involving parallel amalgamation circum microcontinent amalgamation and oroclinal bending the preservation of trapped basins played a significant role in orogenesis with some parts of the oceanic plate being subducted and others behaving as rigid units the orogenesis in the caob was long lived lasting for more than 800 m y involving multiple subduction and long continuous accretion and featuring the complexity of accretionary orogenesis and continent growth

a combined fluid inclusion and s h o he ar isotope study of the devonian ashele vms type copper zinc deposit in the altay orogenic belt northwest china abstract the altay orogenic belt of kazakhstan and china incorporates one of the world class volcanogenic massive sulfide vms polymetallic metallogenic belt more than 12 large and superlarge vms deposits have been found in this belt the ashele basin is located at the western end of the chinese altay bordering kazakhstan and hosts the large ashele copper zinc deposit which is a typical vms deposit and the largest one in this basin the principal orebodies are stratabound and located between basalt and tuff units in the ashele formation the mineralization has a two layered structure that consists of an upper stratiform concordant massive cu zn or barite orebody and a lower veinlet disseminated and stockwork cu or cu pb zn ag orebody associated with silicic alteration several exhalative rocks such as barite hematitic jasper pyrite and silicified units also occur here we investigate the ore forming fluids of the exhalative sedimentary units including jaspilte stratiform barite and cu zn orebodies which carry fluid inclusions that show homogenization temperatures of 100 410 c with two peaks around 230 and 150 c and low salinity clustering between 2 and 8 wt nacl equiv corresponding to nacl h2o fluids the ore forming fluids of the vein orebody and silicified zones are characterized by low to medium temperature peak homogenization temperatures between 120 and 280 c low to medium salinity 0 7 12 3 wt nacl equiv and h2o co2 ch4 n2 nacl fluids the 34s values of barite associated with the stratiform barite orebody range from 20 4 to 21 4 indicating that the sulfur was derived from the seawater the sulfur isotope values of sulfide 3 7 to 7 7 with a mean of 3 1 are similar to those of vms deposits from other parts of the world the host volcanic rocks are inferred to be the major source from which the mineralizing fluid leached the ore forming elements the 3he 4he ratios of fluid inclusions in pyrite are in the range of 0 136 0 260 r ra broadly similar to the helium ratios of the crust the 40ar 36ar ratios range from 394 to 9515 and are higher than those of atmospheric argon the 40ar 4he ratios of the ore fluids range from 0 002 to 0 064 with a mean of 0 034 the helium and argon isotope compositions of fluid inclusions suggest that the ore fluids of the ashele deposit were mainly derived from the crust and were mixed with a minor amount of mantle component the 18osmow values of quartz from the silicified zones and vein orebody range from 8 3 to 11 1 with corresponding 18ofluid values of 4 45 to 2 24 whereas the d values of fluid inclusions are between 140 and 90 the 18osmow values of barite from the stratiform barite orebody range from 7 7 to 9 1 with corresponding 18ofluid values of 3 03 to 1 79 with d values of fluid inclusions showing a range of 162 and 135 the combined isotopic data h o and he ar suggest that the ore forming fluids of the ashele deposit were mainly derived from deep circulation of seawater and mixed with magmatic fluids the decrease in temperature and pressure water rock exchange and changes in the composition of ore fluids played important roles in the ore forming processes of the ashele cu zn deposit

mesozoic volcanogenic massive sulfide vms deposits in mexico abstract volcanogenic massive sulfide vms deposits are the most conspicuous type of deposits that formed during the mesozoic in mexico many mexican vms deposits display classical kuroko type mineral zonation and structure and some of them as cuale and la minita formed in shallow submarine environments the most prospective time window for the formation of vms deposits in mexico comprises the late jurassic and the early cretaceous vms stopped forming during the progressive continentalization of mexico since its metallotectonic processes dominated by extensive tectonics changed giving way to compression during the late early cretaceous new vms deposits did not form until after the opening of the gulf of california mesozoic vms deposits in mexico occur in submarine volcano sedimentary sequences that deposited essentially in association with back arc basins now found roughly along the boundaries between tectonostratigraphic terranes or within juvenile and slightly evolved arcs at the internal parts of the terranes while few others occur on the epicontinental seafloor and hinterlands of eastern mexico vms deposits are especially abundant in the guerrero composite terrane and are also present in the alisitos and parral terranes however new evidence referred in this paper indicate the western continental edge of the cratonic block of oaxaquia as a promising new prospective region for vms deposits interestingly no vms deposits are found in the northern part of the guerrero composite terrane despite the occurrence of marine volcano sedimentary sequences similar to those in the south such absence can be related to differential extensional unroofing much larger in the southern part of the guerrero composite terrane than in the northern part many vms deposits occur along or close to terrane boundaries especially around the guerrero composite terrane this distribution reflects the association between vms deposits and back arc basins which represented the frontal part of terranes or sub terranes that were ultimately accreted to the oaxaquia cratonic block as a consequence vms deposits usually display strong deformation and thrusting and their mineral and compositional zonation can be found overturned due to such common association between these deposits and terrane boundaries that reactivated during the cenozoic vms deposits are especially susceptible to overprinting by later metallogenic processes unrelated to vms producing environments this susceptibility may be held accountable for the complex mineral associations found in the francisco i madero deposit the inclusion fluids in the cuale la minita el rubi tizapa and campo morado deposits have salinities that range from 2 5 to 20 0 wt nacl equiv and temperatures of homogenization from 110 to 420 c although a particular fluid inclusion assemblage with daughter halite and sylvite from a stockwork at the tizapa deposit ranged salinities from 39 7 to 64 7 wt nacl and from 35 9 to 43 5 wt kcl and temperatures of homogenization from 440 to 550 c the general characteristics listed above may account for mineralizing fluids from magmatic marine and modified marine sources the entrainment of cool and oxidizing seawater within upwelling fluids increased as the paleohydrothermal systems waned the waning stages are normally represented by barite rich mineralizations and in the case of the la minita deposit this notoriously outlasted by mn oxide mineralization that reflects even more oxidizing conditions a similar evolution is deduced in cuale which is the only known mesozoic vms deposit in mexico that formed in a shallow submarine environment together with la minita the shallower the formation of vms deposits is the more quickly mineralizing fluids evolve into highly oxidized end members once the paleohydrothermal systems cooled down the extremely high salinity and hot inclusion fluids in tizapa despite the unavailability of further geochemical data are likely to represent magmatic brines that did not undergo significant mixing with seawater as for the temporal evolution of the studied deposits they generally exhibit 1 an increasing magmatic contribution from early to middle stages for both fluids as mineralizing fluids grew hotter and more saline and sulfur and 2 the waning of hydrothermal activity towards the last stages on mineralization which is characterized by the prevalence of seawater as fluids grew cooler and more diluted and oxidizing thus reflecting quite a typical evolution for most vms deposits elsewhere new 34s values for the same vms deposits reflect multiple sources of sulfur in the mineralizing fluids magmatic sedimentary metasedimentary and marine different degrees of dominance of either source for sulfur in these deposits and in their stages of mineralization have been inferred in a way that also responds to a schematic evolution from magmatic to seawater dominated paleohydrothermal systems

orbit and tide error reduction for the first 2 years of topex poseidon data more than 2 years of topex poseidon data repeat cycles 1 81 are processed with orbit and tide error reduction schemes that preserve the oceanic signal the rms crossover difference xd between heights belonging to the same cycle is a good measure of the errors because the real oceanic variability manifests little of itself in times less than 10 days this rms xd is reduced from 10 8 to 8 1 cm after the tide error correction and to 6 0 cm after the orbit error reduction and editing a more than threefold reduction in power even for the remarkably error free topex poseidon data if the mesoscale variability that manages to reveal itself in less than 10 days e g in the western boundary currents and residual coastal tide errors are screened out the global area weighted residual xd is only 4 3 cm implying that for variability studies the residual error is only 3 0 cm for instantaneous point measurements of altimetric sea level away from coastal regions far exceeding the prelaunch mission requirement the important issue of signal preservation which has been shown analytically elsewhere is addressed here directly using data treated with orbit reduction as well as untreated data it is shown that the time compartmentalized orbit error reduction leaves the annual heating and cooling cycle intact as anticipated by the analytical proof whereas conventional orbit error removal procedures would wreak havoc the error of the cartwright and ray 1991 tide model is estimated to be in excess of 5 cm global area weighted rms including shallow seas the crossover difference inducing part of the orbit correction which includes any short term large scale along track variations is estimated to be 3 3 cm along track rms for the joint gravity model 2 orbit the total orbit error is estimated to be 3 5 cm an independent confirmation of estimates based on satellite tracking and other means

declining water budget in a deep regional aquifer assessed by geostatistical simulations of stable isotopes case study of the saharan continental intercalaire summary the stable isotopes of water were used to improve the determination of the groundwater budget of the deep saharan continental intercalaire ci a deep confined aquifer mixing processes between the ci and shallower aquifers have been described in several regional studies over the last few decades based on observed isotopic differences between local water masses here we improve the quantitative determination of the discharge flux of this aquifer in one of its main outlet regions the djeffara plain in tunisia based on geostatistics and a simple mass balance mixing model applied before and after the beginning of extensive pumping in the 1970s first the average values of 18 o and 2 h were precisely documented in the mixing zone between ci water and the local recharge based on conditional simulations using spatially distributed isotopic data together with the available estimate of local recharge and conservative hypotheses on the isotopic end members we estimate the discharge flux of the ci in the djeffara plain at 1 78 1 03 m 3 s 1 in 1970 probably near natural steady state reduced to 1 02 0 58 m 3 s 1 in 2004 under strong anthropogenic pressure related to the drastic increase in pumping rates in the deep ci aquifer during this period considering the general groundwater budget over the entire ci aquifer we estimate a recharge value of 5 13 m 3 s 1 or 6 5 mm yr 1 over the 25 000 km 2 of recharge area in the saharan atlas this value is in line with the evaluation of 2 1 mm yr 1 obtained recently from the grace satellite gravity data for the overall outcrops considering that recharge occurs mostly in the atlas region

in situ la mc icp ms u pb geochronology of igneous rocks in the ashele basin altay orogenic belt northwest china constraints on the timing of polymetallic copper mineralization abstract the altay orogenic belt of kazakhstan hosts a world class polymetallic copper volcanogenic massive sulfide vms metallogenic belt and the eastern margin of this belt extends into the southern chinese altay the ashele basin is located at the western end of the chinese altay and borders kazakhstan the basin hosts the large ashele copper zinc deposit which is a typical vms deposit and the largest deposit in the ashele basin and it hosts the subvolcanic hosted medium sized sarsuk polymetallic gold deposit both of these deposits are hosted in the ashele formation volcanic sequence the ashele copper zinc orebodies are stratabound orebodies located between basalt and tuff units and were formed during exhalative sediment deposition in comparison the sarsuk gold copper lead zinc orebodies are hosted by rhyolite porphyry that contains disseminated veinlet and veinlet stockwork ore that formed during intrusion of the rhyolite porphyry this study presents new zircon la mc icp ms u pb analyses of six volcanic and subvolcanic units and dikes associated with the sarsuk and ashele deposits the ore bearing rhyolite porphyry diabase dike basalt tuff and dacite porphyry samples analyzed during this study yielded ages of 382 0 382 8 381 7 388 2 387 0 and 379 4 ma respectively these data indicate that the ashele formation formed during the early mid devonian 375 402 ma whereas the ashele copper zinc deposit formed during the middle devonian 388 387 ma and the sarsuk polymetallic copper gold deposit formed during the latest middle devonian 382 ma inherited zircons within the six samples analyzed during this study yielded u pb ages of 618 2294 ma suggesting the presence of precambrian crystalline basement within the altay orogenic belt

a revised stratigraphic and tectonic framework for the ashele volcanogenic massive sulfide deposit in the southern chinese altay evidence from stratigraphic relationships and zircon geochronology abstract the ashele volcanogenic massive sulfide vms deposit is the largest and most representative vms deposit in the chinese altay metallogenic belt but its stratigraphic sequence tectonic framework and morphology are debated in this paper on the basis of previous research field investigations excavation pits drill core sampling and new la icp ms u pb analyses of zircons from mafic and felsic volcanic rocks we show that the main structure of the ashele deposit is an overturned tightly closed syncline and that the primary orebody is controlled by this structure moreover we show that the ashele vms deposit displays a double layer structure made up of a feeder zone of veinlet disseminated and stockwork orebodies overlain by massive stratiform orebodies that are folded we revise the stratigraphy of the ashele formation into five conformable sedimentary subsequences based on new field investigations and the zircon geochronology of each subsequence from bottom to top we divide the formation into a siliceous tuff layer 405 1 1 8 ma a dacitic layer 395 9 403 ma a rhyolitic layer 390 9 0 83 ma an orebody layer ca 387 ma and a basalt layer 387 377 ma the early to middle devonian ashele formation unconformably underlies the late devonian qiye formation

stable isotope characteristics of tiemurte pb zn deposit in altay xinjiang lying in kelang basin on the southern margin of altay the tiemurte medium size lead zinc deposit occurs in 2nd lithological member of upper silurian lower devonian kangbutiebao formation with the host rocks being marble chlorite quartz schist calcareous argillaceous siltstone and skarn the ore deposit has experienced three evolutionary periods i e sedimentary exhalative period superposed reforming period and hypergenic period the 34s values of the sedimentary exhalative period range mainly from 27 8 to 16 0 with the peak value being 26 0 and a few values varying from 1 7 to 3 4 suggesting that the ore forming fluid was mainly derived from the mixed fluid of meteoric water and magmatic water in the sedimentary exhalative period d values of quartz and calcite are from 122 to 61 18o values change from 9 5 to 10 9 and 18oh2o values vary from 5 8 to 4 8 implying that the ore forming fluid was probably the mixture of magmatic water meteoric water and metamorphic water the tiemurte lead zinc deposit belongs to vms type subjected to superposed reformation

fluid inclusion noble gas and halogen evidence on the origin of cu porphyry mineralising fluids the naturally occurring noble gas isotopes 40ar 36ar 84kr and 129xe and halogens cl br i have been determined simultaneously in irradiated quartz vein samples by noble gas mass spectrometry quartz vein samples were collected from the potassic and propylitic alteration zones of six porphyry copper deposits pcd bingham canyon utah and silverbell ray mission pinto valley and globe miami in arizona in addition analyses of 3he 4he have been obtained from sulphide minerals hosted by the quartz veins at silverbell ray pinto valley and globe miami the majority of pcd fluids studied have br cl and i cl ratios that overlap those of fluids included in mantle diamond suggesting that the salinity had a juvenile origin the high i cl 121 10 6 mole m in samples from the propylitic zone of silverbell is attributed to the presence of sedimentary formation water 3he 4he ratios have r ra values in the range 0 3 to 1 72 and provide evidence for the involvement of a crustal component in addition to mantle volatiles 40ar 36ar ratios vary from meteoric values of 317 in the propylitic zone of bingham canyon and 323 in the skarn alteration of mission up to 3225 in the potassic zone of pinto valley fluids in both the potassic and propylitic alteration zones of every deposit are a mixture of a low salinity end member comprising meteoric water and air and a high salinity end member consisting of a mixed mantle and crustal fluid the 40ar cl ratio of fluid inclusions at pinto valley 10 4 m is similar to values obtained previously for mantle fluids the 40ar cl value is two orders of magnitude lower at bingham canyon where a depleted 36ar concentration 0 2 10 6 cm3 g below that of air saturated water asw and a range of highly fractionated noble gas compositions f84kr 13 and f129xe 160 indicate that boiling and pulsed fluid flow have occurred

stable isotopic and geochemical identification of groundwater evolution and recharge sources in the arid shule river basin of northwestern china stable isotopic dvsmow and 18ovsmow and geochemical signatures were employed to constrain the geochemical evolution and sources of groundwater recharge in the arid shule river basin northwestern china where extensive groundwater extraction occurs for agricultural and domestic supply springs in the mountain front of the qilian mountains the yumen tashi groundwater ytg and the guazhou groundwater gzg were ca hco3 ca mg hco3 so4 and na mg so4 cl type waters respectively total dissolved solids tds and major ion mg2 na ca2 k so42 cl and no3 concentrations of groundwater gradually increase from the mountain front to the lower reaches of the guazhou basin geochemical evolution in groundwater was possibly due to a combination of mineral dissolution mixing processes and evapotranspiration along groundwater flow paths the isotopic and geochemical variations in melt water springs river water ytg and gzg together with the end member mixing analysis emma indicate that the springs in the mountain front mainly originate from precipitation the infiltration of melt water and river in the upper reaches the lateral groundwater from the mountain front and river water in the middle reaches are probably effective recharge sources for the ytg while contribution of precipitation to ytg is extremely limited the gzg is mainly recharged by lateral groundwater flow from the yumen tashi basin and irrigation return flow the general characteristics of groundwater in the shule river basin have been initially identified and the results should facilitate integrated management of groundwater and surface water resources in the study area copyright 2015 john wiley sons ltd

chemical and isotopic characteristics of groundwater dominated radovna river nw slovenia in order to investigate stream water spring waters and water from a borehole facies weathering processes residence times and average recharge altitudes in the radovna river valley were analysed for their concentrations of dissolved ca2 mg2 k na hco3 cl no3 so4 2 and for the isotope compositions of hydrogen oxygen and dissolved inorganic carbon dic all water samples show a ca2 hco3 water facies with low contents of k na cl no3 and so4 2 water rock interaction and carbonate weathering are the significant contributors to water geochemistry analysis of the water chemistry indicates that waters drain a monolithological terrain and non anthropogenically influenced watershed the 2h and 18o values are seasonally dependent on the snowmelt precipitation and evaporation the average recharge altitudes for all sampling locations are between 1120 and 2130 m the average residence time for the stream water is 2 4 years and for karst springs 1 2 years the 13cdic values in all samples are influenced by dissolution of carbonates degradation of organic matter and by equilibrium with atmospheric co2 all geochemical and isotope analyses show changes in stream water in the downstream direction and are highly dependent on the inflow of karstic spring based on hydrogeological mapping geochemical and stable isotope results a conceptual hydrogeological model of the radovna system in which karstic and alluvial aquifers are in contact was determined

fluid inclusion characteristics and mineralization of dadonggou pb zn ore deposit in altay xinjiang the dadonggou pb zn ore deposit is located in the kelan volcanic sedimentary basin the biggest basin on the southern margin of the altay mountains with the attitude of its ore bodies the same as that of the strata the ore bearing wall rock is mainly volcanic sedimentary rock of the lower devonian kangbutiebao formation and the ores occur in bedded disseminated and veinlet forms ore minerals consist simply of galena sphalerite and pyrite in this paper the authors carried out systemic measurements of homogeneous and freezing temperatures and salinities of fluid inclusions in quartz calcite and sphalerite formed at different ore forming stages in the dadonggou pb zn deposit chromatographic analysis of quartz samples and laser raman spectroscopic analysis of fluid inclusions in quartz and sphalerite were also conducted three main types of fluid inclusions namely nacl h2o inclusions co2 h2o ch4 inclusions and co2 h20 nacl inclusions were identified the homogenization temperatures of the fluid inclusions vary remarkably from 97 3 to 480 mostly in the range of 140 300 the salinities w nacleq of fluids range from 0 2 to 57 1 mostly between 3 2 and 14 8 the gas components of fluid inclusions are mainly co2 and h2o with minor amounts of such components as ch4 n2 and h2 the liquid components of fluid inclusions are mainly na ca2 f and cl subordinately k and so42 and small amounts of mg2 br and no 3 with the calculated ion concentration ranging from 36 6 to 58 0 according to previously analyses of the isotopic composition of c h o and s of the ores the 13cv pdb values of calcite range from 4 2 to 0 4 the dv smow of the inclusions in quartz range from 89 to 127 and the 18oh2o values of quartz and calcite range from 11 4 to 7 6 it is suggested that the ore forming fluid was mainly derived from the mixed meteoric water and magmatic water the carbon in the ore fluid was mainly derived from marine carbonates the change of physicochemical conditions and the immiscibility of co2 h2o exerted the main effect on the ore forming process of the dadonggou pb zn ore deposit

nd sr isotopic mapping of the chinese altai and implications for continental growth in the central asian orogenic belt article i nfo the chinese altai orogen is a typical domain of the central asian orogenic belt and in previous syntheses was divided into six tectonic units or terranes in this paper 41 new and 36 published whole rock nd and sr isotopic data for granitoid intrusions and mafic dykes within units 2 and 3 of the central altai and units 4 to 6 of the southern altai were used for isotopic mapping the age of the samples used is known from u pb zircon dating end t values range from 4 to 2 in the central altai units 2 and 3 and from 1 4 to 6 in the southern altai units 4 and 5 and up to 8 4 in unit 6 correspondingly nd model ages tdm decrease from 1 6 1 1 ga in the central altai to 1 0 0 5 ga in the southern altai except for a continental fragment in unit 4 isr is elevated in the central units decreasing to b0 705 in the southern units 5 and 6 these results demonstrate that the central altai contains widespread old crustal components in its basement whereas the southern altai comprises a higher proportion of juvenile crust when integrated with published u pb zircon ages our data show that new crust grew southwards in the chinese altai in addition our data suggest that units 2 and 3 are a single tectonic unit whereas the southern altai unit 4 which previously was regarded as a single young accretionary terrane should be subdivided into two units a younger arc and an older continental fragment the granitoids in the chinese altai can be divided into syn and post non orogenic groups the syn orogenic granitoids have ca 50 80 mantle derived component whereas the post non orogenic granitoids contain ca 70 90 the generation of syn and post non orogenic granitoids represents horizontal lateral and vertical crustal growth which contributed ca 18 28 and 7 8 respectively to the area of the chinese altai this work shows that isotopic mapping is an effective approach to elucidate terrane composition in the central asian orogenic belt and thereby better constrain palaeozoic crustal growth

using stable hydrogen and oxygen isotopes to reveal monsoonal and related hydrological effects on meteoric water in the western pacific monsoon region a case study of the ilan region northeastern taiwan abstract this study analyzes the isotopic compositions 2h and 18o of meteoric waters including precipitation and stream water to reveal what major hydrological processes affect the hydrological regime of the ilan region northeastern taiwan the isotopic results indicate monsoonal flows as the fundamental factors affecting studied precipitation and stream water summer precipitation sourced from southerly air mass exhibits lower and deuterium excess de values than winter precipitation sourced from northerly air masses the 18o and de values are respectively 7 7 and 8 for summer precipitation and 3 3 and 24 for winter precipitation furthermore semi quantitative estimations using de evidence indicate that summertime southerly air masses generally contribute more to stream water than wintertime northerly air mass flows approximately 54 vs 46 however the contribution fractions are controlled by the orientation of catchments to the windward side of respective monsoonal flows northern catchments located on the windward side of southerly air masses receive about 60 of their water from precipitation condensed from the southerly air masses and 40 from the northerly air masses by comparison southern catchments located on the windward side of northerly air masses receive about 59 of their water from northerly air masses and 41 from southerly air masses additionally catchment effect induced from value is notable in stream basins with high elevations but this is not related to catchment sizes besides this altitude effect which is determined in terms of 18o values was derived using data from four precipitation stations of northern taiwan it ranges from 2 5 to 3 0 per 100 m depending on the season moreover based on the de evidence secondary evaporation effects are apparent with moisture recycling influencing inland summer precipitation and raindrop evaporation influencing inland winter precipitation

element partitioning in sediment soil and vegetation in an alluvial terrace chronosequence limagne rift valley france a landscape geochemical study abstract the geochemical behaviour of specific elements in fluvial sediments topsoils soil profiles and plant material on a sequence of quaternary alluvial terraces was reconstructed semi quantitatively using indices of accumulation or depletion with respect to abundance in the lithosphere local soils and sediments topsoils of different ages and soil profiles are most clearly differentiated by the degree of leaching of ca mg and some minor elements with respect to less mobile si and ti clay translocation within soil profiles of older terraces leads to accumulation of al and associated elements in deeper horizons and accumulation of fe and mn in pseudogley horizons in the upper part of the clay accumulation layers p k ca mn and zn are strongly concentrated in plant materials relative to the topsoils ca is accumulated more strongly in oak bark than in grasses and the relative accumulation is greater on the older terraces due to the low ca content in their topsoils mn contents of both grasses and oak bark are greater on the older terraces than the younger for most elements topsoil and plant material contents show little correlation probably because plant requirements exert a greater control on element uptake than does availability the results illustrate that landscape geochemical analysis is useful for rapid appraisal of long term landscape processes such as erosion sedimentation weathering and preferential plant uptake

metallogenesis and fluid evolution of the huangtupo cu zn deposit east tianshan xinjiang nw china constraints from ore geology fluid inclusion geochemistry h o s isotopes and u pb zircon re os chalcopyrite geochronology abstract the recently discovered huangtupo cu zn deposit is located in the dananhu tousuquan arc east tianshan nw china orebodies are hosted in volcano sedimentary rocks of the late ordovician early silurian daliugou formation the metallogenic physicochemistry ore forming fluids and metallogenesis of the deposit were investigated through orebody features fluid inclusion microthermometry laser raman spectroscopy and synchrotron radiation x ray fluorescence srxrf the results indicate that the deposit includes an upper sedimentary exhalative ore belt stage i as well as a lower vein stockwork ore belt in a hydrothermal fluid supply channel stage ii associated with silicification chloritization epidotization pyrophyllitization and beresitization alteration the re os isochron age of 429 5 10 ma obtained from primary chalcopyrite the la icp ms zircon u pb age of 423 3 2 9 ma for the host hangingwall tuff fluid inclusion fi microthermometry and geological characteristics were applied to constrain hydrothermal processes and ore genesis quartz and barite were collected from the massive sulfide and vein ores for fi study four types of fi were identified liquid rich l type vapor rich v type daughter mineral bearing s type and c type containing co2 h2o stage i barite fis yield homogenization temperatures of 232 364 c peak value 265 c with salinities of 4 85 10 94 wt nacl equiv whereas stage ii quartz fis yield temperatures of 270 400 c peak value 350 c with salinities of 2 41 13 72 wt nacl equiv peak value 6 28 wt laser raman spectroscopy analyses of fi gas compositions indicate that the fis contain mainly h2o with minor co2 and n2 initial ore forming fluids comprise a medium high temperature low salinity system of hot evolved seawater that was cooled and diluted by mixing with cold seawater fluid mixing and local boiling would have facilitated mineralization srxrf analyses indicate that the liquid phase is enriched in cu and zn the 34s values of sulfide indicate that the sulfur was derived from the magma host volcanic rocks oxygen and hydrogen isotopic data also imply that the ore forming fluids were mainly derived from deep circulation of seawater and mixed with minor magmatic fluids the estimated trapping pressures for vein stockwork mineralization fluids range from 20 to 60 bar average 40 bar at a depth of 0 4 km the ore fluids ascenting along faults and fracture networks at or near the seafloor played important roles in oreforming processes of the huangtupo vms cu zn deposit

ore genesis and hydrothermal evolution of the donggebi porphyry mo deposit xinjiang northwest china evidence from isotopes c h o s pb fluid inclusions and molybdenite re os dating

sediment recycling and crustal growth in the central asian orogenic belt evidence from sr nd hf isotopes and trace elements in granitoids of the chinese altay felsic igneous rocks are common constituents of volcanic arcs and contain valuable information about subduction related magmatism in this study we investigate nine granitoids with s type volcanic arc affinity from the chinese altay emplaced from 507 to 391 ma in an active subduction zone during the early middle paleozoic these granitoids are characterized by moderate to high sio2 contents 61 01 75 30 wt moderate total alkalis na2o k2o 3 43 7 64 wt and high al2o3 contents 13 29 17 18 wt negative epsilon nd t values 6 1 to 1 0 the wide range of epsilon hf t values 7 0 to 9 0 and enrichment of liles such as pb th and u all suggest that the granitoids were probably derived from the partial melting of subducting oceanic sediments and the associated mantle wedge this inference is further supported by the nd isotope data the high initial sr 87 sr 86 ratios 0 703963 0 719428 low ba th ratios 7 00 118 93 and uniformly negative end t values 6 1 to 1 0 indicate that slab derived aqueous fluids were vital in generating the initial magma of these granitoids and assimilation played only a minor role our data demonstrate that residual zircon retains a substantial amount of hf during the partial melting of oceanic sediments therefore hf may not be an effective tracer for the input of recycled sediments we conclude that sediment recycling played an important role in the generation of arc magmatism and the growth of the central asian orogenic belt caob c 2016 international association for gondwana research published by elsevier b v all rights reserved

geology geochronology and fluid inclusion studies of the xiaorequanzi volcanogenic massive sulphide cu zn deposit in the east tianshan terrane china the xiaorequanzi cu zn deposit is in the westernmost part of east tianshan terrane in northwestern china the deposit is unique in the region being a volcanogenic massive sulphide vms deposit loc

accretionary orogenesis of the chinese altai insights from paleozoic granitoids zircon u pb dating and whole rock major oxide trace element and nd sr isotope compositions have been determined for four representative granitic intrusions in the sw chinese altai in order to understand the orogenesis and history of crustal growth in the central asian orogenic belt caob the ashile and halatas bodiesare relatively small intrusions formed in the late carboniferous 318 6ma andpermian 267 4ma respectively thelargertarlang tb andkeketuohaibatholiths kb havemagmaticagesof 359 to 412 ma the granitoids consist chiefly of tonalite granodiorite and granite and are metaluminous to weakly peraluminous in composition asi 0 8 1 1 the ashile pluton is characterized by relatively high mgo 2 73 3 54 wt and sr 395 456 ppm contents with low k2o na2o ratios 0 31 0 42 and mantle like nd sr isotopic compositions endt 2 85 to 3 26 initial 87 sr 86 sr 0 7047 0 7051 it probably formed by fractional crystallization of a mantle derived magma with limited assimilation of oldcrustalmaterial theotherintrusionshavenear zeroornegative endtvalues 0 67to 4 41 andhighersrisotopiccompositions initial 87 sr 86 sr 0 7067 0 7092 indicating a mixture of juvenile and old components in their genesis these intrusions are characterized by relatively low k rb cs contents and low rb sr ratios mostly b0 6 and generally exhibit moderate to high heavy rare earth element hree concentrations ybn 8 26 and weak hree fractionation dy ybnb1 5 with or without negative europium anomalies eu eu 0 5 1 0 these characteristics are consistent with an origin by dehydration melting of a hornblendebearing mid crustal source above the garnet stability field dominated by mafic to intermediate rocks this suggests that the deep crust of the chinese altai may contain a considerable proportion of juvenile material mantle derived magmatism probably in an active extensional continental margin setting played an important role in the formation of the chinese altai acting not only as a heat sourceforcrustalmeltingbutasasourceofjuvenilecomponents therelativelysmallvolumesanddistinctgeochemicalcompositions of the ashile and halatas plutons may imply a substantial change in the geodynamic setting in the late paleozoic 2007 elsevier b v all rights reserved

fluid inclusion and noble gas studies of the dongping gold deposit hebei province china a mantle connection for mineralization the dongping gold deposit 100 t au occurs about 200 km inboard of the northern margin of the north china craton the deposit is mainly hosted by syenite of a middle paleozoic alkalic intrusive complex that was emplaced into late archean basement rocks both groups of rocks are intruded by late jurassic to early cretaceous crustal melt granite dikes and stocks some within a few kilometers of the deposit the gold ores were deposited during this latter magmatic period at about 150 ma a time that was characterized by widespread regional north south compression that formed the east west trending yanshan deformational belt the ores include both the telluride mineral bearing low sulfide quartz veins and the highly k feldspar altered syenite with most of the resource concentrated in two orebodies 1 and 70 fluid inclusion microthermometry indicates heterogeneous trapping of low salinity e g 5 7 wt nacl equiv fluids that varied from a few to 60 mole percent nonaqueous volatile species laser raman spectroscopy confirms that the vapor phase in these inclusions is dominated by co2 but may be comprised of as much as 9 mole percent h2s and 20 mole percent n2 methane concentrations in the vapor phase are consistently 1 mole percent the variable phase ratios are consistent with fluid immiscibility during ore formation fluid inclusion trapping conditions are estimated to be 250 to 375 c and 0 6 to 1 0 kbar helium isotope studies of fluid inclusions in ore stage pyrites indicate 3he 4he ratios of 2 1 to 5 2 ra ra 1 4 10 6 for air for orebody 1 and 0 3 to 0 8 ra for orebody 70 the former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1 the lower values for orebody 70 which is characterized by a more disseminated style of gold mineralization are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks which may have contributed additional 4he to the fluids a mantle source for at least some of the components of the gold forming fluid is consistent with upwelling of hot asthenosphere and erosion of as much as 100 to 150 km of cool archean lithosphere beneath the craton during this time the dongping deposit is located along the 100 km wide north south gravity lineament which marks the western border of the thinned crust as both regional metamorphism of mesoproterozoic and younger cover rocks and widespread granite magmatism also occurred at ca 150 ma it is unclear as to whether one or both of these also contributed fluid and or metals to the hydrothermal system importantly these new data suggest that economically significant gold deposits of similar mineral style and fluid composition which are scattered along the margins of the craton may all be products of a fluid originally partly sourced within the mantle

a combined fluid inclusion and s pb isotope study of the neoproterozoic pingshui volcanogenic massive sulfide cu zn deposit southeast china abstract the pingshui cu zn deposit is located in the jiangshan shaoxing fault zone which marks the neoproterozoic suture zone between the yangtze block and cathaysia block in south china it contains 0 45 million tons of proven ore reserves with grades of 1 03 wt cu and 1 83 wt zn this deposit is composed of stratiform massive sulfide ore bodies which contain more than 60 vol sulfide minerals these ore bodies are hosted in altered mafic and felsic rocks spilites and keratophyres of the bimodal volcanic suite that makes up the neoproterozoic pingshui formation metallic minerals include pyrite chalcopyrite sphalerite tennantite tetrahedrite and magnetite with minor galena gangue minerals are quartz sericite chlorite calcite gypsum barite and jasper three distinct mineralogical zones are recognized in these massive sulfide ore bodies a distal zone composed of sphalerite pyrite barite zone i an intermediate zone characterized by a pyrite sphalerite chalcopyrite assemblages zone ii and a proximal zone containing chalcopyrite pyrite magnetite zone iii a thin layer of exhalative jaspilite overlies the sulfide ore bodies except in the proximal zone the volcanic rocks of the pingshui formation are all highly altered spilites and keratophyres but their trace element geochemistry suggests that they were generated by partial melting of the depleted mantle in an island arc setting homogenization temperatures of the primary fluid inclusions in quartz from massive sulfide ores are between 217 and 328 c and their salinities range from 3 2 to 5 7 wt nacl equivalent raman spectroscopy of the fluid inclusions showed that water is the dominant component with no other volatile components fluid inclusion data suggest that the ore forming fluids were derived from circulating seawater the 34 s values of pyrite from the massive sulfide ores range from 3 6 to 3 4 indicating that the sulfur was primarily leached from the arc volcanic rocks of the pingshui formation both pyrite from the massive sulfide ores and plagioclase from the spilites have similar lead isotope compositions implying that the lead was also derived from the pingshui formation the low lead contents of the massive sulfide ores and the geochemistry of their host rocks are similar to many vms cu zn deposits in canada e g noranda and thus can be classified as belonging to the bimodal mafic subtype the presence of magnetite and the absence of jaspilite and barite at the 505 m level in the pingshui deposit suggest that this level is most likely the central zone of the original lateral massive sulfide ore bodies if this interpretation is correct the deep part of the pingshui cu zn deposit may have significant exploration potential

a review of cu dominant mineral systems in the kalatag district east tianshan china abstract the chinese east tianshan is the easternmost sector of the tianshan mountain range in the central asian orogenic belt caob and accommodates several events of magmatism crustal growth and mineralization the kalatag arc is unique in the east tianshan due to its widespread early paleozoic volcanic rocks which offers a special opportunity to study the early paleozoic cu dominant mineral systems in island arc setting in this region nine deposits have been discovered in recent years these deposits occur in paleozoic volcanic rocks between the kalatag fault and kabei fault and can be divided into six mineral systems i e vms cu zn epithermal cu porphyry cu au skarn fe cu magmatic cu ni sulfide and hydrothermally overprinted deposits among them vms epithermal porphyry skarn and magmatic cu ni sulfide mineralization are distributed in the southeastern central northwestern and westernmost kalatag respectively the mineralization and associated intrusive rock ages can be clustered into four episodes in the kalatag arc i e late ordovician silurian ca 450 430 ma middle devonian ca 390 380 ma late carboniferous ca 320 300 ma and permian ca 280 ma here paleozoic granitoids show similar geochemistry and isotopic features all paleozoic granitoids plot in the subalkaline field and predominantly tholeiitic to calc alkaline series with enrichment of large ion lithophile elements and depletion of high field strength elements these granitoids plot in a volcanic arc fields in tectonic discrimination diagrams which are characteristic of an island arc setting the fluid inclusions in porphyry and skarn system are characterized by high temperature high salinity low content of co2 whereas epithermal system represented by low temperature low salinity low content of co2 and the vms system can be described as medium temperature medium low salinity co2 bearing fluid h o isotopic data suggest that ore fluids were sourced from a mixing fluid between magmatic and meteoric water s pb isotopic data show that the sulfur mainly came from magma or ore hosting igneous rocks the yudai porphyry cu au deposit the hongshi epithermal cu deposit and the honghai au rich vms cu zn deposit formed at the same time related to a subduction environment the early paleozoic vms mineralization is generally overprinted by late magmatic hydrothermal fluids which may be due to multiple accretionary orogeny in kalatag island arc we propose that the north dipping subduction of the paleo tianshan ocean or south dipping subduction of the junggar ocean during late ordovician silurian which may led to the development of yudai porphyry copper hongshi epithermal copper and honghai vms copper zinc deposits in the kalatag arc after that north dipping subduction of the paleo tianshan ocean resulted to the formation of the middle devonian ca 390 380 ma and late carboniferous ca 320 300 ma cu mineralization finally the permian ca 280 ma magmatic copper nickel sulfide deposits associated with ultramafic mafic complexes developed in post collisional extension setting part of a large igneous province lip event associated with mantle plume upwelling

kinetic and mineralogic controls on the evolution of groundwater chemistry and 87sr 86sr in a sandy silicate aquifer northern wisconsin usa abstract substantial flowpath related variability of 87sr 86sr is observed in groundwaters collected from the trout lake watershed of northern wisconsin in the extensive shallow aquifer composed of sandy glacial outwash groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter lake uplands 87sr 86sr of groundwater derived mainly as seepage from a precipitation dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase in contrast 87sr 86sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed due to suppression of plagioclase dissolution together with preferential leaching of sr from radiogenic phases such as k feldspar and biotite the results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic sr whereas stagnant waters obtain relatively radiogenic sr nearly the entire range of strontium isotope composition observed in groundwaters from the watershed was measured in the experimental product waters the constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions in contrast episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution perhaps due to accumulation of clay mineral nuclei on its reactive surfaces differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior this study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations

mantle crustal and atmospheric noble gases in ailaoshan gold deposits yunnan province china abstract helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the ailaoshan gold province china the province is a series of gold deposits hosted on a 200 km segment of a major normal fault formed during eocene extension the deposits have been well characterised using conventional geochemical and microthermometric techniques the results of which are consistent with a predominantly high temperature magmatic fluid present in the ore minerals in contrast analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle derived magmatic fluid and two different low temperature fluids similar to modern groundwaters the specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle derived component and a surface derived component to these fluids the magmatic fluid dominates deposits from the northern end of the fault the second groundwater is present only in deposits in the south of the province by assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature 3he heat ratios can be estimated the 3he heat ratios vary systematically along the fault from 30 10 12 cm3 stp j 1 in the northern deposits to

isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer the allier river valley france summary hydrodynamic hydrochemical and isotopic investigations were carried out on 18 points including boreholes piezometers and surface waters from february 2011 to august 2012 to assess groundwater quality in the unconfined shallow alluvial aquifer of the allier river one of the main tributary of the loire river the study area located near the city of clermont ferrand france plays an important socio economic role as the alluvial aquifer is the major source of drinking water for about 100 000 inhabitants the objective of the project aims at understanding the functioning of alluvial aquifers that occupy a pre eminent position in the hydrogeologic landscape both for their economic role production of drinking water and agricultural development and for their ecological role moreover this study also targets at determining the factors and processes controlling shallow groundwater quality and origin the water circulates from the south with a natural alimentation from the hills in the non pumped part of the alluvial aquifer in the pumping zone this general behaviour is altered by the pumping that makes the water from the allier river enter the system in a large proportion four end members have been identified for the recharge of the alluvial groundwater rainfall allier river surrounding hills aquifer and the southern non pumped part of the alluvial system results indicate that despite the global ca hco 3 water type of the groundwater spatial variations of physico chemical parameters do exist in the study area ionic concentrations increase from the allier river towards east due either to the increase in the residence time or a mixing with groundwater coming from the aquifer s borders stable isotopes of the water molecule show the same results boreholes close to the river bank are recharged by the allier river depleted values while boreholes far from the river exhibit isotopic contents close to the values of hills spring or to the southern part of the alluvial aquifer both recharged by local precipitation one borehole b65 does not follow this scheme of functioning and presents values attesting of a probable sealing of the allier river banks based on these results the contribution of each end member has been calculated and the functioning of the alluvial system determined

identification of different groundwater flowpaths within volcanic aquifers using natural tracers for the evaluation of the influence of lava flows morphology argnat basin chaine des puys france hydrochemical and stable isotopic 2h 18o data were used to characterize the groundwater flow and major chemical features within a complex fractured volcanic aquifer system the argnat basin which is located in the chaine des puys french massif central from 10 sampling points the study of the transfer into the saturated zone from upstream to downstream given the geological context and topography allows to estimate the role of supply from high and low altitudes to the recharge processes this work shows the existence of different types of supply between pahoehoe and a a flows therefore the morphology of volcanic flows impacts the chemical and isotopic signatures of groundwater enhancing or reducing the influence of the unsaturated zone on the pathways of infiltrated water pahoehoe flows imply horizontal water flows of low discharge at the top of the lava whereas a a flows seems to be much more heterogeneous and locally able to promote the existence of perched water bodies and further vertical circulations taking into account these two types of behaviour a conceptual scheme of the functioning of this heterogeneous environment is proposed which will help towards a sustainable management of volcanic aquifers in relation with the european union groundwater directive 2006 118 ce 2006

hydrogeochemical controls on shallow alluvial groundwater under agricultural land case study in central portugal a hydrogeochemical study employing graphical multivariate statistical and modeling tools was conducted in an area of alluvial deposits in the mondego river basin to determine the factors and processes controlling the shallow groundwater chemistry groundwater was collected from 29 observation wells in six sampling campaigns between march 2001 and september 2002 samples were analyzed for basic physicochemical parameters major ions and some minor ions hierarchical cluster analysis was applied to the data set including both the spatial and temporal monitoring data and resulted in the definition of eight distinct water types with the aid of hydrochemical and physicochemical scatter plots it was possible to identify the main processes controlling the groundwater chemistry 1 evapotranspiration and recharge 2 calcium and magnesium carbonate and co2 dissolution 3 nitrate leaching from agriculture 4 oxidation and reduction and 5 cation exchange these processes are frequently common to more than one water type but unique in combination and or extent in space and or time geochemical modeling of the water types using phreeqc allowed the validation and to a certain extent quantification of the processes that affect the shallow groundwater evolution these tools can provide an essential support for the assessment of groundwater vulnerability to contamination and for the elaboration of groundwater resource management strategies

resolving mantle and crustal contributions to ancient hydrothermal fluids hear isotopes in fluid inclusions from dae hwa wmo mineralisation south korea abstract helium and argon isotopes from fluid inclusions in individual colour zones b c d and e of a large scheelite crystal from the 88 ma dae hwa w mo deposit south korea trace the source and history of the ore fluids a gradual decrease of the fluid 3 he 4 he 3 he 36 ar and 40 ar 36 ar from the core to the edge of the scheelite reflects the progressive dilution of a magmatic fluid by meteoric water and is consistent with the previously observed decrease of 18oh2o and fluid inclusion homogenisation temperatures th shelton et al 1987 the covariation of fluid inclusion he ar isotope systematics with 18o and th defines a magmatic component with 3 he 4 he 1 2 10 6 3 he 36 ar 0 01 and 40 ar 36 ar 1000 anomalously high helium and argon isotope ratios in zone d fluids represents undiluted magmatic noble gases this may reflect local variation in the magmatic gas flux or gas loss due to boiling of the hydrothermal fluids prior to mixing with magmatic gas helium and argon isotope systematics constrain mantle and crustal components in the hydrothermal fluids 40 ar 3 he 4 5 104 are close to the mid ocean ridge basalt value implying that 40ar is mantle in origin radiogenic isotope ratios of the mantle endmember 40 ar 4 he 0 69 0 06 are similar to contemporary geothermal fluids the coincidence of mantle derived he and ar in the fluids is strong evidence that mantle melting during late cretaceous subduction triggered the crystal melting responsible for granite formation 40 ar 4 he of the meteoric fluid 0 007 0 001 is far lower than the crystal production ratio 0 2 implying an origin in crust below 200 c

hydrogeochemical processes in shallow quaternary aquifers from the northern part of the datong basin china groundwater is the most important source of water supply in datong city however the levels of shallow quaternary groundwaters from urbanized areas have been declining continuously and groundwater quality deteriorating in recent years understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in datong mineral hydrolysis of alumino silicate minerals such as plagioclase and clinopyroxene is the primary process controlling the concentration of h4sio4 in the study area speciation calculations using the geochemical modeling code phreeqc indicated that hydrolysis of bedrock mainly composed of basalt and metamorphic rocks is the major hydrogeochemical process controlling groundwater chemistry the study area can be divided into 3 hydrogeochemical zones a recharge unimpacted zone b intermediate industry impacted zone and c discharge agriculture impacted zone ion exchange and industrial and or agricultural contamination contribute to the increase of na from zone a to zone c where the concentration of no3 is up to 461 5 mg l with a mean value of 101 5 mg l indicating that agricultural practice seriously affects groundwater sulfate concentration in groundwaters in an alluvial fan at datong is extremely high up to 1172 9 mg l and shows a close relationship with the concentrations of trace elements especially ni and co indicating that coal mining is the main contamination source for groundwater from the alluvial fan in addition to agricultural activities

distribution of porphyry deposits in the eurasian continent and their corresponding tectonic settings in the eurasian continent there are three huge metallogenic belts of cu and mo porphyry deposits comprising the paleozoic central asian ore belt in the north the tethyan eurasian ore belt of jurassic to cenozoic age in the southwest and the east margin ore belt of the eurasian continent of jurassic to cretaceous age in the east the latter is considered to be part of the vast circum pacific ore belt some of the main features of the spatial temporal distribution of cu and mo porphyry systems and related geodynamic processes of the three metallogenic belts are described in particular the key role of postsubduction related porphyry ore systems is emphasized comprising collisional and post collisional cu mo porphyry deposits during the geological history of the eurasian continent the recurrent feature of these ore systems and related felsic rocks is their derivation from partial melting of stagnant or residual oceanic slabs and mixing with a variable amount of crustal material during magma ascent to shallower levels 2013 published by elsevier ltd

a hydrogeological and hydrochemical explanation of the groundwater composition under irrigated land in a mediterranean environment algarve portugal in the campina de faro in the south of portugal agricultural practices have a large impact on groundwater composition these practices involve pumping of water for irrigation from combinations of large diameter shallow wells noras and small diameter deep boreholes furos excess irrigation water returns to the aquifer and mixes with water from the regional groundwater flow system this irrigation return flow is concentrated by strong evapotranspiration and by flushing of fertilisers the concentration increase induces cation exchange whereby ca on the soil exchanger is replaced by na the mixing in the aquifer allows application of a mixing cell model which may then be used to calculate transmissivities from the cl mass balance the calculations are complicated by the time variant behaviour of cl and the method is adjusted to calculate the change of chloride in time results from the calculations appear to be in good agreement with hydrochemical observations

isotope signatures and hydrochemistry as tools in assessing groundwater occurrence and dynamics in a coastal arid aquifer groundwater from the la paz arid coastal aquifer in baja california mexico is essentially the only source of drinking water for the local population and tourists as well as irrigation water for agricultural needs the intensive exploitation of the aquifer and water cycling has resulted in groundwater abatement up to 10 m and high salinity up to 5800 mg l 1 a study using hydrochemistry isotopic deuterium oxygen 18 and carbon 14 and gaseous tracers chlorofluorocarbons cfc 11 cfc 12 cfc 113 as well as multivariate statistics was developed to elucidate groundwater composition flow and occurrence groundwater is of meteoric origin and a large proportion is subject to evaporation the primary natural recharge is generated in the el novillo and las cruces ranges and groundwater subsequently flows in a se nw direction toward the coast the initial water type is the result of discordant dissolution of silicate minerals and ion exchange on soils in the lower plain portion the aquifer system is recharged from irrigation return flow and seawater intrusion which significantly affects groundwater chemistry nitrate and chloride concentrations indicate that groundwater is highly affected by an overuse of fertilizers in agricultural activities but there is little effect from urban activities seawater intrusion has progressed rapidly during the past decade and the impact currently extends 13 km inland radiocarbon residence time calculations suggest that groundwater is modern with the exception of chametla and el centerario sites in the central and western lowlands with ages of up to 5000 years these waters indicate an additional recharge source for the upconing of fossil groundwater or regional flow

a magnetite rich cyprus type vms deposit in ortaklar a unique vms style in the tethyan metallogenic belt gaziantep turkey abstract the ortaklar vms deposit is hosted in the kocali complex consisting of basalts and deep sea pelagic sediments which formed by rifting and continental break up of the southern neotethyan in late triassic the basalts are of nmorb type without notable crustal contamination from the surface to depth the ortaklar deposit consists of a gossan zone a thick massive ore zone and a poorly developed stockwork zone primary mineralisation is characterised by distinctive facies including sulphide breccias proximal graded beds distal stockworks and chimney fragments ore mineral abundances decrease in the order of pyrite magnetite chalcopyrite and sphalerite two distinct phases of mineralisation massive magnetite and massive sulphide are present in the ortaklar deposit textural evidence e g magnetite replacing sulphides and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages the transition from sulphide to magnetite mineralisation is interpreted to relate to variation in h2s content of ore fluids the 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in fe and h2s the 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in fe but poor in h2s replacing the pre existing sulphide ore the alteration patterns mineral paragenesis lithological features massive ore stockwork ore gossan of the ortaklar deposit together with its trace elements cu pb zn au ag and ree signatures are all consistent with a cyprus type vms system the 34s values in pyrite and chalcopyrite samples range from 2 6 to 5 7 indicating that the hydrothermal fluids were associated with sub seafloor igneous activity typical of cyprus type vms deposits however magnetite formed later than sulphide minerals in the ortaklar deposit contrasting with typical cyprus type vms deposits where magnetite generally occurs in lower sections consequently although the ortaklar deposit generally conforms to cyprus type deposits it is distinguished from them by its late stage and high magnetite concentration thus the ortaklar deposit is thought to be an exceptional and perhaps unique cyprus type vms deposit

modeling of geochemical processes and multivariate statistical analysis for hydrochemical assessment of spring water of the outer himalaya india water resources in the himalayan region are under stress because of the changes in land use and land cover pattern and climate in the recent past the region has encountered extreme events such as cloud burst and widespread flooding in this reference this study was conducted on the spring water resources in the outer himalayan region to assess their quality and quantity the main geochemical processes and the impact of anthropogenic forcing on water chemistry were deciphered using geochemical modeling tools multivariate statistical analysis and graphic plots the hierarchical cluster analyses were used to categorize the springs in two clusters based on their chemical characteristics the principal component analysis was used to evaluate the effective loading of spring water hydrochemical data ionic ratios and geochemical modeling using phreeqc were used to confirm the processes that govern the chemistry of the spring water the results indicate that silicate weathering and anthropogenic activities are the dominant processes controlling the chemical evolution of spring water in the region this study will provide a better insight for understanding the spring water resources and their sustainable management in the himalayan region