occurrence of old groundwater in a volcanic island on a continental shelf an example from nakano shima island oki dozen japan summary groundwater residence times in nakano shima island oki dozen japan which is situated on the continental shelf are discussed based on groundwater age indices cfcs 3 h and 14 c stable isotopic ratios of hydrogen d oxygen 18 o carbon 13 c and noble gases 3 he 4 he and 4 he 20 ne samples were taken from springs shallow wells up to 5 m deep water supply wells about 10 100 m deep and the hot spring well 866 m deep d and 18 o of all the samples plot along meteoric water lines indicating a meteoric water origin isotope values of the hot spring water were slightly lower than other samples most samples from springs shallow wells and the water supply wells contained higher cfcs and 3 h while samples from two water supply wells w4 and w7 and the hot spring well showed much lower cfcs concentrations this result indicates that mixing ratios of old groundwater that is free of cfcs and 3 h were higher for these samples 14 c concentrations of samples with lower cfcs were measured and corrected for addition of 14 c free dissolved inorganic carbon the corrected 14 c concentration of the hot spring water was lower than that of the water supply well indicating mixing of much older groundwater in the hot spring water because of lower corrected 14 c concentration and lower d and 18 o values groundwater from the hot spring well is considered to be recharged in a colder climate than present day because the island is situated on the continental shelf the seafloor around the island was most likely widely exposed during the last glacial period one possible explanation for the existence of groundwater showing lower d 18 o and 14 c concentrations such as the hot spring water is that fresh groundwater recharged when sea level was lower still remains after transgression without being replaced by salt water

ice sheet sources of sea level rise and freshwater discharge during the last deglaciation we review and synthesize the geologic record that constrains the sources of sea level rise and freshwater discharge to the global oceans associated with retreat of ice sheets during the last deglaciation the last glacial maximum 26 19 ka was terminated by a rapid 5 10 m sea level rise at 19 0 19 5 ka sourced largely from northern hemisphere ice sheet retreat in response to high northern latitude insolation forcing sea level rise of 8 20 m from 19 to 14 5 ka can be attributed to continued retreat of the laurentide and eurasian ice sheets with an additional freshwater forcing of uncertain amount delivered by heinrich event 1 the source of the abrupt acceleration in sea level rise at 14 6 ka meltwater pulse 1a 14 15 m includes contributions of 6 5 10 m from northern hemisphere ice sheets of which 2 7 m represents an excess contribution above that derived from ongoing ice sheet retreat widespread retreat of antarctic ice sheets began at 14 0 15 0 ka which together with geophysical modeling of far field sea level records suggests an antarctic contribution to this meltwater pulse as well the cause of the subsequent younger dryas cold event can be attributed to eastward freshwater runoff from the lake agassiz basin to the st lawrence estuary that agrees with existing lake agassiz outlet radiocarbon dates much of the early holocene sea level rise can be explained by laurentide and scandinavian ice sheet retreat with collapse of laurentide ice over hudson bay and drainage of lake agassiz basin runoff at 8 4 8 2 ka to the labrador sea causing the 8 2 ka event

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

some isotopic constraints on the evolution of the granulite and upper amphibolite facies terranes in the eastern musgrave block central australia abstract the central to eastern musgrave block central australia consists of the meso to neoproterozoic fregon and mulga park subdomains that are separated by a zone of mylonites and pseudotachylytes known as the woodroffe thrust the subdomains were previously considered to have undergone different geological histories but the differences relate mainly to metamorphic grade the fregon subdomain attained at least transitional granulite facies metamorphic conditions and the mulga park subdomain reached upper amphibolite facies felsic gneisses from both the fregon and mulga park subdomains contain zircons that are structured with euhedral centres overgrown by round elongate rims ion microprobe u pb analyses of the cores yield ages of 1557 24 and 1554 28 ma respectively and are interpreted to represent the time of igneous crystallization these ages place a maximum age constraint on the deposition or emplacement of the gneiss precursor high grade metamorphism grading from upper amphibolite to granulite facies took place between 1200 and 1150 ma and prior to the intrusion of several granitoid suites at around 1150 ma the kulgera adamellite and ayers ranges adamellite granitoid suites of the fregon subdomain yield ion microprobe u pb crystallization ages of 1150 12 and 1152 11 ma respectively a concordant u pb isotope dilution analysis on the ayers ranges adamellite yields a more precise age of 1152 3 ma the porphyritic suite intruding the mulga park subdomain yield an ion microprobe u pb magmatic age of 1159 20 ma these emplacement ages indicate extensive grenvillian felsic magmatism not previously recognized in australia the woodroffe thrust formed during a period of substantial crustal shortening the petermann orogeny 550 ma when the fregon subdomain was thrust onto the mulga park subdomain synkinematic muscovite and biotite record k ar and rb sr ages between 560 and 520 ma this petermann event is not recorded in the fregon subdomain due to confinement of the strain and associated mineral recrystallization to the underlying mulga park subdomain we suggest that the granulites were not exposed prior to the petermann orogeny as the basal quartzites of the amadeus basin occur only on the amphibolite facies mulga park subdomain

crustal architecture of central australia based on deep seismic reflection profiling abstract the crustal architecture of central australia is interpreted from deep seismic reflection profiling conducted by the australian geological survey organisation in two surveys in 1985 and 1993 the seismic traverses oriented normal to the main surface structures ran north south in central australia and crossed parts of the arunta block amadeus basin musgrave block and officer basin the present crustal fabric was set in place by the end of the mesoproterozoic by about 1100 ma reactivation of the structures took place in a continental intraplate setting mainly during the middle late palaeozoic alice springs orogeny but also during other orogenic events in the arunta block the crust is dominated by major north dipping planar structures interpreted as thick skinned thrusts many of these thrusts cut deep into the crust and at least one the redbank thrust zone appears to cut and offset the moho in contrast in the northern musgrave block limited field mapping and teleseismic data suggest that the major crustal scale planar structures are south dipping in the central to southern amadeus basin deformation is essentially thin skinned with north directed thrusting confined to the sedimentary succession thus the deep seismic profiles in central australia show a present day crustal architecture that is the response of the crust to mesoproterozoic terrane amalgamation and to later reactivation by intraplate deformational events therefore central australia is a model for intraplate cratonic deformation that occurs in continental crust that is cold thick and strong

past and future grounding line retreat of the west antarctic ice sheet the history of deglaciation of the west antarctic ice sheet wais gives clues about its future southward grounding line migration was dated past three locations in the ross sea embayment results indicate that most recession occurred during the middle to late holocene in the absence of substantial sea level or climate forcing current grounding line retreat may reflect ongoing ice recession that has been under way since the early holocene if so the wais could continue to retreat even in the absence of further external forcing

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

cenozoic marine sedimentation and ice volume variation on the east antarctic craton recycled cretaceous and cenozoic marine microfossils have been recovered from samples of the pliocene sinus formation samples were collected from outcrops in the reedy beardmore and ferrar glacier areas of the transantarctic mountains between lat 77 and 86 s the glaciogene sediments contained diatoms foraminifera calcareous nannoplankton silicoflagellates radiolarians sponge spicules palynomorphs and ostracodes of late cretaceous paleocene eocene late oligocene late miocene and pliocene age this suggests the presence of open marine basins on the east antarctic craton during late mesozoic and cenozoic time the apparent absence of early oligocene and early through middle and earliest late miocene assemblages suggests either that marine regression exposed the basin floors or that ice filled the basins during these times the high elevation setting of sirius formation outcrops suggests one of two hypotheses for their origin 1 they are in situ pliocene glaciomarine deposits that were uplifted 1 750 2 500 m with the transantarctic mountains to their present elevation 2 the sirius formation deposits are a mixture of derived sediments stripped from sub ice intracratonic basins and subsequently redeposited by ice flowing up the inland slope of the transantarctic mountains we favor the second hypothesis with transport to sites sometime within the past 3 m y

controls on subaerial erosion rates in antarctica erosion rates offer insight on landscape development and the relative importance of chemical and physical processes of weathering minimal chemical weathering makes antarctica an ideal location in which to compare the physical weathering of carbonate rocks to other lithologies here we report the first cosmogenic nuclide derived erosion rates for carbonate rocks in antarctica carbonate samples collected in the southernmost ellsworth mountains reflect a 36cl erosion rate of 0 22 0 02 mm ka this erosion rate is consistent with other reported antarctic erosion rates but is lower than 36cl erosion rates derived from other arid regions in the world these results are integrated with a continent wide reanalysis of 28 erosion rate studies 200 measurements which comprise numerous rock types and other cosmogenic nuclides by combining cosmogenic nuclide derived erosion rates across studies the larger trends provide insight into factors e g lithology glacial history and availability of abrasive material affecting subaerial erosion rates in antarctica statistical analysis of the compiled data set shows differences based on lithology with sandstone having the largest range of erosion rates the compiled data also reveals higher erosion rates in areas with a large potential sediment supply like the dry valleys samples collected from boulders yield lower erosion rates than those collected from bedrock likely due to a combination of physical processes that affect boulders and bedrock differently and glacial history which can affect the apparent cosmogenic nuclide derived erosion rate

cosmogenic nuclides 10be and 26al imply limited antarctic ice sheet thickening and low erosion in the shackleton range for 1 m y concentrations of the cosmogenic nuclides 1 0 be and 2 6 al on bedrock surfaces in the shackleton range antarctica indicate minimum exposure ages between 3 0 03 and 1 16 0 10 ma the isotope data indicate that the maximum long term erosion rate is 0 10 0 35 m m y and the ratios suggest no prolonged periods of burial by cold based ice the findings are important because of the location of the massif close to the junction of the east antarctic ice sheet and the landward extent of the filchner ice shelf these results point to three conclusions first the massif has not been overridden by the east antarctic ice sheet during the late quaternary rather moraines 200 340 m above outlet glaciers are likely to represent the maximum thickening of the filchner ronne ice shelf during the quaternary second the high radionuclide concentrations on bedrock surfaces one of which is striated suggest that some glacial landforms were created in at least pliocene or more likely miocene time third the exceptionally low erosion rates imply that the modern cold arid climate has persisted for millions of years these findings provide evidence of old stable landscapes over a wider area of antarctica than the mc murdo dry valleys

constraints and deception in the isotopic record the crustal evolution of the west musgrave province central australia abstract the hf and nd isotopic evolution of the musgrave province central australia is used to constrain the timing of crust formation and lithospheric organisation of proterozoic australia the dataset from this region challenges two widely held tenets of hf and nd isotope systematics namely that crust formation events can only be identified as periods when crystallisation ages correspond to model ages and that linear hf evolution arrays away from depleted mantle along crustal lu hf or sm nd slopes reflect reworking of the same source hf isotopes in musgrave province zircon crystals indicate two major crust formation events at c 1900 ma and at 1600 1550 ma although no juvenile rocks or crystals are known from c 1900 ma radiogenic addition into the crust at this time is required to account for consistent nd and hf evolution patterns which show no indication of an initially heterogeneous source oxygen isotopes in zircon grains confirm that much of the c 1900 ma hf isotopic signal is not compromised by mixtures furthermore the correspondence between mantle extraction and the commencement of reworking of archean material supports new crust generation at c 1900 ma and a coupling between lower and upper crustal processes the c 1900 ma timing of juvenile addition is dissimilar to that in the albany fraser and arunta orogens and may reflect continental arc development on the margin of a southern continent the general hf isotopic evolution trend of the musgrave province apparently reflects reworking from a dominant c 1900 ma source with some additional unradiogenic and radiogenic input through time however in the 1220 1050 ma interval this apparent isotopic evolution contrasts with geological observations that indicate input of voluminous mantle derived material intracontinental rifts and other regions with sustained very high temperature crustal recycling processes generate magmatic provinces with extreme hfse enrichment this can have a profound influence on isotopic evolution trends suppressing typical juvenile addition patterns isotopic mixture modelling indicates that a significant volume of mantle derived material can be accommodated within hfse enriched magmas without diverging isotopic signatures from apparent reworking trends in the musgrave province the crust had become so hfse enriched during the prolonged musgrave orogeny 1220 1150 ma that it was insensitive to mantle input which is estimated to have been as much as 85 during this event

minimum 10be exposure ages of early pliocene for the table mountain plateau and the sirius group at mount fleming dry valleys antarctica using accelerator mass spectrometry ams we have measured 10be and 26al in quartz from granites and sandstones from table mountain and mount fleming antarctica our data show that the plateau surface at table mountain had formed by early pliocene time at the latest granites fringing but within the sirius group at table mountain give a minimum exposure age of 2 6 ma for this deposit a sandstone clast on the ferrar dolerite surface just outside and below and thus postdating the sirius group has a minimum age of 2 9 ma two samples from the sirius group at mount fleming have 10be concentrations that have reached secular equilibrium this deposit is at least 4 8 m y old the sirius group at mount fleming cannot have been deposited after 3 0 2 5 ma as implied by biostratigraphic data our dates contradict the hypothesis that in the pliocene east antarctica was deglaciated and the climate was significantly warmer and wetter the preservation of these surfaces indicates a continuous cold desert in the dry valleys since the beginning of the pliocene the high 10be concentrations we have measured cannot be reconciled with uplift of the transantarctic mountains at a rate of 1 km m y during the past 3 m y

east antarctic deglaciation and the link to global cooling during the quaternary evidence from glacial geomorphology and 10be surface exposure dating of the sor rondane mountains dronning maud land abstract reconstructing past variability of the antarctic ice sheets is essential to understand their stability and to anticipate their contribution to sea level change as a result of future climate change recent studies have reported a significant decrease in thickness of the east antarctic ice sheet eais during the last several million years however the geographical extent of this decrease and subsequent isostatic rebound remain uncertain in this study we reconstruct the magnitude and timing of ice sheet retreat at the sor rondane mountains in dronning maud land east antarctica based on detailed geomorphological survey cosmogenic exposure dating and glacial isostatic adjustment modeling three distinct deglaciation phases are identified for this sector during the quaternary based on rock weathering and 10 be surface exposure data we estimate that the ice sheet thinned by at least 500 m during the pleistocene this thinning is attributed to the reorganization of southern ocean circulation associated with global cooling into the pleistocene which reduced the transport of moisture from the southern ocean to the interior of eais the data also show that since the last glacial maximum the ice surface has lowered less than ca 50 m and that this lowering probably started after ca 14 ka this suggests that the eais in dronning maud land is unlikely to have been a major contributor to postglacial sea level rise and meltwater pulse 1a

proterozoic evolution and tectonic setting of the northwest paterson orogen western australia abstract the proterozoic igneous deformation and metamorphic histories of the palaeoproterozoic rudall complex in the northwestern paterson orogen can be linked to those of the arunta inlier in central australia and in part with the capricorn orogen in central western australia the similarities in deformation and metamorphic histories for these widely separated regions indicate a palaeoproterozoic continent continent collisional event between the palaeoproterozoic west australian and north australian cratons between c 1830 and 1765 ma in the paterson orogen this palaeoproterozoic collisional event resulted in the yapungku orogeny which included thrust stacking of clastic sedimentary and volcanic rocks deposition of the protoliths for the c 1790 ma siliciclastic paragneiss succession contemporaneous with granitic intrusion and metamorphism up to granulite facies during this 65 million year period the arunta inlier and capricorn orogen were deformed metamorphosed at medium to high grades and intruded by granitoids during the strangways orogeny in the arunta inlier and the capricorn orogeny in the capricorn orogen the neoproterozoic tarcunyah throssell and lamil groups are clastic sedimentary sequences that were deposited after 1070 ma in the northwestern paterson orogen and deformed by the miles orogeny before 678 ma the miles orogeny produced a northwesterly trending fold and fault system of tight to isoclinal upright and overturned folds and thrust faults the orogeny may have been coincident with the c 750 720 ma areyonga tectonic movement affecting the arunta inlier and the lower neoproterozoic part of the amadeus basin in central australia at c 550 ma the paterson orogeny which is most likely equivalent to the petermann orogeny in the musgrave complex of central australia deformed the northwestern paterson orogen and was preceded by local intrusion of granites the similarities of styles and timing of deformation in the northwestern paterson orogen arunta inlier and capricorn orogen indicate that these three regions were probably linked during most of the proterozoic

evidence for a late wisconsin glaciation of the weddell sea the huge ice shelves in west antarctica the ross and filch ner ronne ice shelves have probably extended out on the continental shelf during the late wisconsin1 previous discussions which have focused on the ross sea have suggested 1 that the ice extended across the whole continental shelf2 3 or 2 that there was only a minor expansion4 here we present sedimentological data from the weddell sea fig 1 which suggest that a late wisconsin grounded ice sheet extended to the shelf edge the evidence includes a recent thicker ice in ellsworth mountains at the head of the filchner ronne ice shelf5 this thickening would lead to an expansion of the inland ice sheet over the continental shelf filling up the weddell sea embayment

the musgrave province stitching north west and south australia abstract the musgrave province in central australia is an east west trending 120 000 km2 region composed of lithologic units that range in age from earliest mesoproterozoic to neoproterozoic it is one of the few terrains in australia that records significant grenvillian aged tectonism and has a distinctly younger geological history than the surrounding fragments of proterozoic australia compared to other proterozoic terranes of australia the evolution of the musgrave province is poorly understood the region contains evidence for the development of earliest mesoproterozoic arc related magmatism with major juvenile crustal additions comprising intercalated felsic and mafic gneisses with protolith ages ranging from ca 1 60 to 1 54 ga this period of arc magmatism was followed by closure of the ocean separating the north australian craton nac from the south australian craton sac at ca 1 54 ga arc magmatism and collision was followed by a period of extension during which protoliths to the metasedimentary rocks of the eastern musgrave province were deposited at ca 1 4 ga the combined juvenile nd isotopic signature and detrital zircon ages from these metasediments suggests provenance from non australian sources with possible sources originating from laurentia granitic magmatic events occurred at ca 1 3 and 1 20 1 14 ga the latter comprising the voluminous a type granites of the pitjantjatjara supersuite the intrusion of these magmatic units provide key temporal constraints on deformational events and are coeval with the voluminous a type suites of laurentia which would invite correlation of australia with laurentia at ca 1 30 1 14 ga these magmatic episodes are accompanied by deformation at granulite facies at ca 1 30 ga unnamed event and 1 23 1 15 ga musgrave orogeny these deformation metamorphic events have completely recrystallised any primary layering within the pre 1 30 ga rocks forcing interpretations on their genesis to be inferred from geochemical and isotopic data the tectonic significance of these events is not clear however they may form part of a larger grenville aged deformational belt extending into the western australian albany fraser province and antarctica emplacement of the voluminous mafic ultramafic giles complex and associated granulite facies metamorphism of the giles event occurred at ca 1 078 ga the layered intrusions of the giles complex are generally fault bound and are considered to represent discrete bodies emplaced in an extensional regime associated with generation of the warakurna large igneous province the ca 1 08 ga alcurra dolerite unnamed ca 1 0 ga olivine dolerites and ca 0 8 ga amata dolerite dissect much of the musgrave province the alcurra dolerite and unnamed olivine dolerite dykes have been proposed as originating from a modified sub continental lithospheric mantle whereas the amata dolerite is proposed to be plume related coinciding with the initiation of rifting creating the centralian superbasin an earliest cambrian intraplate transpressional event is recorded in the ca 550 ma petermann orogeny this resulted in deep crustal exhumation of much of the northern musgrave province from beneath the centralian superbasin with mylonitic deformation recorded at pressures of 12 kbar and temperatures of 700 750 c

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

monazite behaviour and age significance in poly metamorphic high grade terrains a case study from the western musgrave block central australia abstract integrated in situ textural chemical and electron microprobe age analysis of monazite grains in a migmatitic metapelitic gneiss from the western musgrave block central australia has identified evidence for multiple events of growth and recrystallisation during poly metamorphism in the mesoproterozoic garnet sillimanite bearing metapelite underwent partial melting and segregation to palaeosome and leucosome during metamorphism between 1330 and 1296 ma with monazite grains in leucosome recording crystallisation at 1300 ma monazite breakdown during melting is inferred to have occurred in the palaeosome during a subsequent granulite facies event at 1200 ma deformation and metamorphism of leucosome and palaeosome resulted in partial disturbance of ages and potential minor growth on 1300 ma monazite in leucosome growth of new high y hree monazite in palaeosome domains occurred during garnet breakdown in the presence of sillimanite to cordierite and spinel as a result of post peak isothermal decompression diffusive enrichment of resorbed garnet rims in y hree suggests garnet breakdown occurred slower than volume diffusion of ree monazite in both palaeosome and leucosome were subsequently partially to penetratively recrystallised during a retrogression event that is suggested to have occurred at 1150 1130 ma the intensity of recrystallisation and disturbance of ages appears linked to proximity to retrogressed garnet porphyroblasts and their occurrence in the relatively reactive or fertile local environments provided by the palaeosome mesosome volumes which caused localised changes in retrogressive fluids towards compositions more aggressive to monazite like reaction textures it is apparent that domainal equilibrium and reaction may control or at least strongly influence monazite ree and u th pb chemistry and hence ages

foreign contemporaries unravelling disparate isotopic signatures from mesoproterozoic central and western australia abstract extensive time constrained isotopic sm nd lu hf datasets on samples with well studied geological context demonstrates that the musgrave province of central australia and the albany fraser orogen of south western australia evolved through temporally similar mesoproterozoic orogenies at 1345 1260 and 1215 1140 ma but on completely different basement the west and north australian cratons amalgamated before the 1345 1260 ma event which saw the convergence and final amalgamation of those combined cratons with the south australian craton well defined nd and hf isotopic evolution arrays for the musgrave province reflect a juvenile basement with distinct 1950 1900 1600 1550 ma crust formation events rare non radiogenic material is seen only in detritus and in magmas that assimilated this material this evolved detritus was derived from non yilgarn archean sources and reworked archean sources which were added to sedimentary basins developed over the musgrave province basement during and after c 1400 ma to the south of the musgrave province the madura province has a similarly radiogenic signature to the musgrave province and is likely contiguous with it beneath younger cover sequences it shows 2 0 1 4 ma mantle extraction ages and is dominated by juvenile rocks reflecting oceanic crust consumed to the north of the south australian craton and east of the west australian craton available data support the suggestion that the musgrave province is simply modified madura province crust situated along the edge of the north australian craton together the musgrave province and the madura province represent proterozoic australia s most juvenile crustal remnant in stark contrast to this juvenile remnant the isotopic evolution array for the albany fraser orogen reveals a much more evolved signature charting progressive juvenile input into an archean source with strong isotopic and age similarity to the yilgarn craton of the west australian craton

microtextures microchemistry and mineralogy of basaltic glass alteration jeju island korea with implications for elemental behavior the meteoric alteration of basaltic glass in hyaloclastite 0 55 to 0 2 ma from jeju island korea was examined using high resolution electron microscopy in situ sample preparation using focused ion beam and microchemical analysis the glass particles showed a sequential development of alteration textures toward the glass interior as follows oscillatory zoning of smectite and amorphous bands hemispheres congruent dissolution of glass with smectite infilling in interparticle pore and the replacement of nanogranular amorphous aggregate naa for porous leached glass lg followed by a partial crystallization of smectite chemical compositions of lg widely varied from partial to complete leaching of almost all kinds of cations to a preferred leaching of na only the order of leaching in lg followed na mg 2 ca 2 fe 2 al 3 ti 4 leached cations were removed from the hyaloclastite water system or incorporated into secondary phases sodium was all but removed from the system magnesium was largely lost with partial incorporation into smectite calcium was significantly retained in naa partly incorporated into the smectite interlayer and partly lost iron and al were partitioned between naa and smectite titanium was mostly retained in naa and ti rich silicates the molar ratio of major cations to si was reversed from ca 2 mg 2 na in basaltic glass to na mg 2 ca 2 in groundwater the geochemical evolution of pore water was influenced by the microtextural and microchemical evolution of glass particles and vice versa systematic microtextural microchemical and mineralogical analyses of natural glass alteration are critical to understanding the long term behavior of glass alteration

magnetotelluric constraints on the tectonic setting of grenville aged orogenesis in central australia abstract magnetotelluric mt data were collected over a 480 km long profile in central australia extending from the mesoarchaean palaeoproterozoic gawler craton into the mesoproterozoic neoproterozoic musgrave province the two regions have contrasting geological histories and many reconstruction models of proterozoic australia propose that they were juxtaposed during the mesoproterozoic despite the significant differences in geological background between the gawler craton and the musgrave province the mt data did not image an electrical structure or any change in electrical character between them mt models suggest that southern central australia is electrically separated into two parts the first comprising the northernmost gawler craton and the musgrave province has a 5 km thick layer of moderate resistivity overlying highly resistive crust the second comprising the central northern gawler craton displays moderate resistivity to the base of the crust the lithospheric mantle underlying both electrical regions is uniformly highly resistive our results suggest that the musgrave province and gawler craton are more closely related than is currently recognized we propose that the gawler craton forms basement to the musgrave province and that the grenvillian musgrave orogeny was an intracratonic reworking event that overprinted the older basement

geological and palaeomagnetic significance of the kulgera dyke swarm musgrave block nt australia summary the kulgera dyke swarm consists of olivine tholeiites which have intruded late proterozoic transitional granulite gneisses and granites of the eastern musgrave block in central australia preliminary rb sr results suggest that the dolerites were emplaced at 1054 f 14ma in addition a rb sr age of 1060 f 10ma on a biotite from a pegmatite indicates thermal resetting of the country rock minerals during dyke emplacement palaeomagnetic investigations of the dykes yield a primary thermoremanent magnetization direction corresponding to a palaeomagnetic pole at 17 s 266 e ag5 12 in addition to this primary magnetization an overprint component was present in many of the samples providing a palaeomagnetic pole at 30 s 138 e ags 24 which is similar to previous results from other central australian rocks affected by the alice springs orogeny the results extend the area of influence of the carboniferous alice springs orogeny southward into the musgrave block further the results provide no evidence for an earlier late proterozoic petermann orogeny affecting the musgrave block in the kulgera region however the possibility that a petermann orogeny thermal overprint has been erased by the alice springs orogeny cannot be dismissed

submarine groundwater discharge revealed by aerial thermal infrared imagery a case study on jeju island korea submarine groundwater discharge sgd is a global phenomenon that carries large volumes of groundwater and dissolved chemical species such as nutrient metals and organic compounds to coastal zones we report the influence of sgd on the coastal waters of jeju island korea using high resolution aerial thermal infrared tir mapping techniques and field investigations an aircraft based system was implemented using a cost effective tir camera for aerial tir mapping ground based calibrations and system integration with gps imu global positioning system inertial measurement unit were performed for the aerial systems the aerial surveys showed distinct low temperature signatures of sgd along the coasts of jeju island revealing large groundwater inputs from the coastal aquifers to the ocean multiple aerial surveys over a range of seasons and tidal stages revealed that sgd rates dynamically affect the sea surface temperature sst of the coastal zone the in situ measurements supported that sgd has a substantial influence on the coastal water chemistry as well as sst our observations highlight the extent to which aerial based tir mapping can serve as a powerful tool for studying sgd and other coastal processes copyright 2016 john wiley sons ltd

garnet orthopyroxene plagioclase quartz barometry refinement and application to the english river subprovince and the minnesota river valley recent experimental theoretical and thermodynamic studies permit better calibration of two reactions for geobarometry grossular pyrope quartz anorthite enstatite grossular almandine quartz anorthite ferrosilite if both reactions are applied using the same thermodynamic data and activity models they should yield the same pressure for a given garnet pyroxene plagioclase quartz assemblage application to a variety of high grade terrains generally yielded excellent results however poor results have been obtained for high fe rocks which can be traced to errors in activity models for garnet and or pyroxene either a two site ideal mixing model for orthopyroxene cf wood and banno 1973 underestimates enstatite activity for high fe orthopyroxenes or the ganguly and saxena 1984 model overestimates pyrope activity in low mg garnets

smnd mineral isochron ages of late proterozoic dyke swarms in australia evidence for two distinctive events of mafic magmatism and crustal extension two distinctive events of widespread dyke intrusion have been identified in central southern australia crystallization ages of the dykes were determined using sm nd mineral isochrons obtained by splitting clinopyroxene and plagioclase into different magnetic and density fractions respectively the stuart dyke swarm in the southern arunta inlier and the kulgera dyke swarm in the eastern musgrave inlier define essentially identical crystallization ages of 1076 33 and 1090 32 ma respectively marking the first episode of post orogenic mafic magmatism in the region two samples from the gairdner dyke swarm in the stuart shelf yield sm nd mineral isochron ages of 867 47 and 802 35 ma respectively whilst two samples from the amata suite in the central musgrave inlier 790 40 and 797 49 ma these four ages represent the second episode of mafic magmatism in central southern australia these ages allow new constraints to be placed on the timing of large scale crustal extension and formation of intracratic depositional basins in the region initial nd values of 7 8 to 6 6 for the stuart dykes and 0 7 for the kulgera dykes suggest they were derived from different mantle sources with the stuart dykes being produced from strongly enriched sources in contrast positive and relatively uniform initial nd values of 2 5 to 4 1 for the younger amata suite and gairdner dykes indicate that they were derived from relatively depleted and homogeneous mantle sources the 1076 33 ma sm nd age of the stuart dyke swarm is significantly older than its rb sr mineral isochron age of 897 9 ma previously reported suggesting mobility of rb and or sr and partial resetting of rb sr isotopic systematics this study demonstrates that reliable and relatively precise sm nd ages can be obtained for precambrian dykes despite the limited number of mineral phases available in the dykes

hydrogeochemical and isotopic evidence of groundwater salinization in a coastal aquifer a case study in jeju volcanic island korea abstract in order to identify the origin of saline groundwater in the eastern part of jeju volcanic island korea a hydrogeochemical and isotopic study has been carried out for 18 observation wells located in east and southeast coastal regions the total dissolved solid contents of groundwaters are highly variable 77 21 782 mg l oxygen hydrogen sulfur and strontium isotopic data clearly show that the saline water results from mixing of groundwater with seawater strontium isotopic compositions and br cl and i cl ratios strongly suggest that the source of salinity is modern seawater intrusion hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation exchange reactions the highly permeable aquifers at the east coastal region are characterized by low hydraulic gradient and discharge rate and high hydraulic conductivity as compared with other regions these properties enhance the salinization of groundwater observed in the study area based on the cl br and 18 o data seawater was determined to have intruded inland some 2 5 km from the coastline considering the poor correlation of sampling depth and cl concentrations observed the position of seawater freshwater interface is not uniformly distributed in the study area due to heterogeneities of the basaltic aquifers

using principal components analysis and na cl ratios to trace groundwater circulation in a volcanic island the example of reunion abstract the development of the limited groundwater resources of a remote tropical island in particularly rugged volcanic terrain requires a thorough understanding of the hydrogeology the cost of a classical approach by borehole investigations often precludes a reasoned approach resulting in a somewhat haphazard development of resources wuth varying success this paper describes the use of multivariate statistical analysis to trace groundwater circulation in volcanic terrains the method involves the use of principal components analysis pca based on both structural and hydrochemical parameters of 243 springs of reunion western indian ocean as a result we propose the use of na cl analysis in differentiating three types of volcanic aquifers this analysis is consistent with a geological and hydrogeological conceptual model developed from a combined hydrochemical and geological reconnaissance of 27 springs

the age and pb loss behaviour of zircons from the isua supracrustal belt as determined by ion microprobe ion microprobe uthpb analyses of zircons from a conglomeratic metavolcanic unit in the isua supracrustal belt of west greenland show that their magmatic age is3807 1ma and failed to detect any older zircon cores or xenocrysts low u areas within zircons at a 30 m scale lost only small amounts of radiogenic pb and only in the recent past whereas high u areas within grains lost much greater proportions of their pb both recently and as early as the archaean some areas in the zircons have concordant upb and thpb ages the ion probe results agree with earlier determinations for the isua supracrustals and clarify minor discrepancies between previous multigrain and single crystal analyses

timing of mesoproterozoic tectonic activity in the northwestern gawler craton constrained by 40ar 39ar geochronology abstract an array of northeast trending shear zones in the north west gawler craton of south australia has been implicated in widely disparate proterozoic continental reconstructions these shear zones are interpreted to have formed in response to sinistral transpression and dissect the north west gawler craton into several geological domains each with contrasting metamorphic histories new 40ar 39ar data provide age constraints for movement along these shear zones and are interpreted to indicate that the karari tallacootra and coorabie shear zones were last active at 1450 ma despite distinct differences in metamorphic grade the various geological domains bounded by shear zones exhibit evidence for commonality in event histories prior to deformation at 1450 ma albeit at different crustal levels this is interpreted to indicate that deformation at 1450 ma was responsible for reshuffling of crustal blocks that were already adjacent rather than amalgamation of exotic terranes the new data also provide additional evidence for a widespread metamorphic and deformational event at 1530 1550 ma across the north western gawler craton the timing of deformation at 1450 is 100 ma younger than suggested in several published tectonic reconstructions and importantly is also significantly older than grenvillian age tectonism in adjacent provinces to the west and north

stable isotopic and geochemical data for inferring sources of recharge and groundwater flow on the volcanic island of rishiri japan abstract an isotopic and chemical study was conducted on precipitation spring water streams groundwater wells and submarine groundwater discharge sgd to constrain the recharge areas and flow paths of sgd the isotopic values of precipitation were used to determine the local meteoric water lines lmwls of rishiri island the d excess values of precipitation showed seasonal variation with lows of 2 5 in the summer and highs of 24 2 in the winter the d excess values of spring water streams groundwater wells and sgd ranged from 12 5 to 23 0 indicating that the resulting waters were a mix of two seasons of precipitation the isotopic composition of the groundwater wells sampled along the coast and sgd showed more negative values than that of the spring water sampled along the coast this indicated that sgd recharged at high altitudes and flowed into the sea the isotopic and chemical composition of sgd indicated unidirectional flow from land to sea

estimating recharge in fractured aquifers of a temperate humid to semiarid volcanic island jeju korea from water table fluctuations and cl cfc 12 and 3h chemistry summary groundwater table fluctuations wtf chloride mass balance cmb apparent groundwater chlorofluorocarbon cfc 12 ages and tritium 3 h mean residence times were used to assess recharge rates on jeju island korea where groundwater is the main source of potable water given the limitations of various techniques and the respective data the methods yield median values of 687 mm yr wtf 429 mm yr cmb 423 mm yr cfc 12 and 394 mm yr 3 h which are lower than the multi annual 1993 2002 average value calculated using the soil water budget swb method 911 mm yr these underestimates are mainly due to most groundwater samples used for the analyses being located in the more arid lowland areas of the island all methods yield highest recharge rates in the southern and eastern districts of jeju implying a strong control of rainfall on the spatial recharge distribution the spatial variability of recharge at the catchment scale is caused by spatially and temporally variable rainfall and evapotranspiration as well as the wide range in effective porosity and specific yield values of the aquifer lithologies the wtf method yields reliable results in the coastal regions where low hydraulic gradients prevail the cmb technique underestimates the recharge values of the swb in all geographic districts probably as a result of anthropogenic cl additions to groundwater and unaccounted for atmospheric cl dry deposition median recharge estimates from the cfc 12 and 3 h data show the lowest spatial correlation with those from the swb mainly as a result of vertical anisotropies and uncertainties in the determination of effective aquifer thicknesses particularly in the perched high level areas the here applied methods are useful for local calibration and validation of swb estimates in lower parabasal regions where thin unsaturated zones prevail however due to their inability to predict recharge in the more remote upslope areas from which as of yet no groundwater data could be obtained they cannot be applied to predict average recharge values representative for the whole island

using h and o isotopic data for estimating the relative contributions of rainy and dry season precipitation to groundwater example from cheju island korea abstract a comparison of deuterium excess or d values of precipitation and groundwater at cheju island korea indicates that unlike in many temperate climates precipitation during the whole year contributes to groundwater recharge this in turn suggests that evapotranspiration effects are minimal consistent with the fact that the island contains highly permeable volcanic rocks overlain by thin soils this hypothesis is contrary to current water budget models that ascribe a significant role to evapotranspiration processes three coastal springs and several streams and ponds throughout the island have enriched 18 o and d values that plot off the local meteoric water line and have relatively high cl concentrations this relationship is suggestive of seawater mixing for the coastal springs and evaporation for the streams and ponds this database thus provides a useful means for evaluation of groundwater resources of the island

holocene deglaciation of marie byrd land west antarctica surface exposure ages of glacial deposits in the ford ranges of western marie byrd land indicate continuous thinning of the west antarctic ice sheet by more than 700 meters near the coast throughout the past 10 000 years deglaciation lagged the disappearance of ice sheets in the northern hemisphere by thousands of years and may still be under way these results provide further evidence that parts of the west antarctic ice sheet are on a long term trajectory of decline west antarctic melting contributed water to the oceans in the late holocene and may continue to do so in the future

multi scale integrated structural and aeromagnetic analysis to guide tectonic models an example from the eastern musgrave province central australia abstract in many polydeformed precambrian provinces the understanding of their tectonic history is limited by insufficient exposure which leads to difficulty in developing links between local and regional architecture and results in poorly constrained models of their regional scale architecture high resolution aeromagnetic data allows interpretation and modelling at a scale comparable to structural mapping and by integrating these methods these links can be developed with high confidence as an example we integrate structural mapping aeromagnetic data interpretation and 3d magnetic inversions in a multi scale structural analysis of the polydeformed eastern musgrave province in central australia deformation during the ca 1200 ma musgravian orogeny is characterised by an originally northeast trending structural grain defined by shear zones and tight to isoclinal folds at all scales 3d magnetic inversion models of syn to post musgravian granites indicate that this structural grain is predominantly west dipping this architecture suggests that a northeast oriented fold and thrust belt developed as a result of northwest southeast compression in central australia during the musgravian orogeny the next deformation event is characterised by an array of originally east southeast trending shear zones that truncate and offset the musgravian structural grain with apparent dextral displacements of up to 1 km these shear zones are commonly co located with mafic and granitic dykes suggesting a dilational origin and they are interpreted to have initiated under northeast southwest extension during the ca 1080 ma giles event the architecture of these two mesoproterozoic events was later extensively overprinted by two deformation events during the pan african aged ca 550 ma petermann orogeny the first is characterised by the widespread reactivation of mesoproterozoic structures resulting in a network of shear zones of variable orientation and the second is characterised by the development of crustal scale transpressional shear zones motion on which has caused the rotation of lithospheric blocks and the reorientation of prior structural trends by up to 90 collectively the architecture of these two events suggests broadly north south crustal shortening in central australia as an intraplate response to gondwana assembly this example demonstrates that the integration of structural geology with aeromagnetic interpretation and modelling can be used to develop high confidence links between local and regional structures these links permit the derivation of better constrained models of major tectonic events particularly in regions where outcrop is poor and the structural architecture is complex

geometry of a large scale low angle midcrustal thrust woodroffe thrust central australia the musgrave block in central australia exposes numerous large scale mylonitic shear zones developed during the intracontinental petermann orogeny around 560 520 ma the most prominent structure is the crustal scale over 600 km long e w trending woodroffe thrust which is broadly undulate but generally dips shallowly to moderately to the south and shows an approximately top to north sense of movement the estimated metamorphic conditions of mylonitization indicate a regional variation from predominantly midcrustal circa 520 620 c and 0 8 1 1 gpa to lower crustal 650 c and 1 0 1 3 gpa levels in the direction of thrusting which is also reflected in the distribution of preserved deformation microstructures this variation in metamorphic conditions is consistent with a south dipping thrust plane but is only small implying that a 60 km long n s segment of the woodroffe thrust was originally shallowly dipping at an average estimated angle of 6 the reconstructed geometry suggests that basement cored thick skinned midcrustal thrusts can be very shallowly dipping on a scale of many tens of kilometers in the direction of movement such a geometry would require the rocks along the thrust to be weak but field observations e g large volumes of syntectonic pseudotachylyte argue for a strong behavior at least transiently localization on a low angle near planar structure that crosscuts lithological layers requires a weak precursor such as a seismic rupture in the middle to lower crust if this was a single event the intracontinental earthquake must have been large with the rupture extending laterally over hundreds of kilometers

baseline geochemical characteristics of groundwater in the mountainous area of jeju island south korea implications for degree of mineralization and nitrate contamination summary hydrogeochemical characteristics of groundwater were investigated to elucidate baseline quality for basaltic aquifers of a mountainous area dominated by natural land cover in the volcanic island of jeju south korea principal component analysis pca resulted in four principal components pc of which pc1 pc3 and pc4 represented natural mineralization by water rock interaction while pc2 corresponded to anthropogenic contamination from nitrate sources hierarchical cluster analysis hca was performed to assess the effect of the geochemical and hydrologic processes on each sample six sample groups distinguished by total dissolved solids tds nitrate concentration and water type resulted from the hca high altitude springs low mineral water nitrate contaminated water intermediate mineral water and two groups of high mineral water water types were transformed from na mg ca hco 3 for low mineral water to na hco 3 for high mineral water nitrate contaminated water occurred near the boundary of natural and agricultural land uses of the western area high mineral water had higher calcite saturation states than other groups the high mineral water also had tritium 3 h values lower than 1 5 tu indicating a significant contribution of old groundwater in contrast low mineral water had tritium values of about 3 tu which is close to those of rainwater geographically the high mineral water was concentrated in the southwestern area where intermediate mineral water was also found this distribution was likely related to the presence of extensive trachytic rocks which could have formed locally isolated aquifers enabling prolonged water rock interactions the higher location of low permeability hydrovolcanic tuffs in the subsurface of the southern area would also increase chances of tapping aquifers below the hydrovolcanic tuffs the cumulative probability of tds showed two breakpoints of 50 and 150 mg l that distinguished high altitude springs low mineral water and high mineral water the cumulative probability of nitrate provided possible threshold values for anthropogenic contamination of 2 5 and 5 5 mg l that 32 of samples had nitrate concentrations higher than 2 5 mg l indicated high vulnerability to surface contamination sources in this mountainous area hca seems to be more effective for interpreting the baseline chemistry of groundwater than other threshold calculating statistics in that hca revealed geochemical processes including natural mineralization and anthropogenic contamination our study suggests that the cumulative probability and hca are useful as complementary methods for determining threshold values

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

flow paths and mixing properties of groundwater using hydrogeochemistry and environmental tracers in the southwestern area of jeju volcanic island summary groundwater from springs test boreholes and domestic wells was investigated to assess the flow system of basaltic aquifers at base flow conditions in the southwestern part of jeju island south korea this study utilized hydrogeochemical parameters and environmental tracers of 18 o 2 h 3 h and chlorofluorocarbons cfcs which showed that well connected flow paths exist between coastal springs regardless of flow rates in contrast test boreholes near the coastal springs exhibited various flow paths nitrate concentrations were much higher than baseline values in mountainous groundwater while those decreased in coastal areas was seemingly contributed from nitrate contamination sources and seawater sources were minimal due to low permeability layers near sea level the water stable isotopes indicated little evaporation and were comparable to the local meteoric water line during the rainy season which was confirmed by deuterium excess values demonstrating that effective infiltration primarily occurs during the rainy season from the effects of altitude on 18 o the mean recharge altitudes for both mountainous and coastal springs were estimated as 300 400 m which implies longer flow paths for the coastal springs the relationship of cfc 12 cfc 113 and that of cfc 12 3 h concordantly indicated that the groundwater consists mainly of binary mixtures composed of 15 25 year old young water and old water with ages greater than 60 years lower nitrate levels in the coastal springs were well represented by the mixing models recharge altitudes for coastal springs increased up to 700 m assuming that old water corresponds to high altitude recharge using the binary mixing model integration of hydrochemical and environmental tracer characteristics revealed that pahoehoe lava flows and hydrovolcanic tuffs play key roles in controlling the groundwater occurrence and quality

thermal rheological and kinematic conditions for channelized lower crustal flow in a threshold example abstract lower crustal flow zones occur in large and hot orogens and rifts where they occur in association with large areas possessing high gravitational potential energy gpe and low lower crust viscosity lower crustal flow zones are also known from regions where neither the rheological nor gpe conditions are sufficiently well developed for widespread flow to occur for these examples the conditions required to form crustal flow zones are less well defined one such case occurs within the ca 600 530 ma petermann orogeny in central australia this work investigates the conditions under which this flow zone developed considering differences with the adjacent regions where flow is not observed a transect of crustal structure in the central petermann orogen is developed that takes into account geological and geophysical data including time constrained pressure and temperature estimates for the petermann orogeny the deformation of this region is reconstructed showing that lower crustal flow was driven by high amplitude crustal scale folding the folding extruded the lower crust towards the foreland causing crustal thickening and buoyant uplift of the orogenic core channelized lower crustal flow is not known from either the eastern or western parts of the orogen and a comparison with these regions suggests three main conditions are required firstly the lower crust must be sufficiently hot and volatile rich to allow melt weakening secondly crustal rheology must allow ductile deformation of the mid to lower crust without high strength layers finally a high degree of lateral confinement is required to form pressure gradients capable of driving flow these three conditions were met only in the central petermann orogen and not in the east or the west this example of a lower crustal flow zone illustrates the combined influence of thermal rheological and kinematic threshold conditions on the initiation and development of channelized lower crustal flow in orogens

groundwater residence time and movement in the maltese islands a geochemical approach the maltese islands are composed of two limestone aquifers the upper and lower coralline limestone separated by an aquitard the blue clay the lower coralline limestone is overlain in part by the poorly permeable globigerina limestone the upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall frequent detections of coliforms suggest a rapid route to groundwater however the unsaturated zone has a considerable thickness in places and the primary porosity of the upper coralline limestone is high so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures measurement of sf6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 years the main sea level aquifers msl on both malta and gozo have a large unsaturated thickness as water levels are close to sea level on malta parts of the aquifer are capped by the perched aquifers and more extensively by the globigerina limestone the limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features transmissivity is low and tritium and cfc sf6 data indicate that saturated zone travel times are in the range 15 40 years on gozo the aquifer is similar but is more extensively capped by impermeable blue clay cfc data show the saturated zone travel time is from 25 years to possibly more than 60 years groundwater age is clearly related to the extent of low permeability cover the 13c signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence perched aquifers malta msl gozo msl the 18o and 2h enriched isotopic signature of post 1983 desalinated water can be seen in more modern groundwater particularly the urbanised areas of the perched and malta msl aquifers in all aquifers movement of solutes from the surface travelling slowly through the matrix provide a long term source of groundwater contaminants such as nitrate

regional high pressure metamorphism during intracratonic deformation the petermann orogeny central australia the petermann orogeny is a late neoproterozoic to cambrian c 560 520 ma intracratonic event that affected the musgrave block and south western amadeus basin in central australia in the mann ranges within the central musgrave block mesoproterozoic granulite facies gneisses granites and mafic dykes have been substantially reworked by deep crustal non coaxial strain of late neoproterozoic to early cambrian age dolerite dykes have recrystallized to garnet granulite facies assemblages associated with the development of a mylonitic fabric at p 12 13 kbar and t 700 750 c migmatization is restricted to discrete shear zones which represent conduits for hydrous fluids during metamorphism peak metamorphism was followed by decompression to c 7 kbar reflecting exhumation of the terrane along the south dipping woodroffe thrust in scattered outcrops north of the mann ranges peak metamorphism occurred at p 9 10 kbar and t c 700 c the woodroffe thrust separates these deep crustal mylonites from granites that were metamorphosed during the petermann orogeny at p c 6 7 kbar and t c 650 c the similarity in peak temperatures at different crustal levels implies an unusual thermal regime during this event the existence of a relatively elevated geotherm corresponding with th and k enriched granites that were in the mid crust during the petermann orogeny suggests that radiogenic heat production may have substantially contributed to the thermal regime during metamorphism this potentially has implications for the mechanisms by which intra plate strain was localized during this event

assembly of proterozoic australia implications of a revised pole for the 1070 ma alcurra dyke swarm central australia summary the pole position for the late mesoproterozoic alcurra formerly kulgera dyke swarm ads musgrave block central australia has been revised by adding new data from two more dykes a palaeomagnetic fold test is positive at the 99 percent confidence level and the pole position is latitude 2 8 s longitude 80 4 e dp 7 2 dm 10 7 new 40ar 39ar determinations on single biotite grains from country rock gneiss 20 cm from the contact with an alcurra dyke yield ages from 1068 2 ma to 1085 2 ma 2 in addition 40ar 39ar determinations on two samples of aggregates of very fine grained biotite from the mesostasis of a stuart dyke sd arunta inlier northern territory yield ages of 1059 2 and 1066 3 ma 2 these new ages are in agreement with those of the 1070 ma warakurna large igneous province west central australia indicating that both the ads and sd belong to that suite palaeomagnetic poles determined by others for the ads and sd are indistinguishable from each other but cannot be presently combined as a single pole because the published information on the sd is incomplete an analysis of the palaeogeography implied by the dispersed palaeomagnetic poles from members of the extended warakurna suite shows that the present relationships between the major precambrian cratons west north and south australian which constitute australia west of the tasman line are inconsistent with the inferred relationship at 1070 ma nor is it apparent that internal deformations within the separate cratons are the cause of the dispersion our findings imply that these major australian cratons must have finally assembled sometime after 1070 ma

high resolution aeromagnetic data over central australia assist grenville era 1300 1100 ma rodinia reconstructions 1 high resolution aeromagnetic data covering the polydeformed and poorly exposed musgrave province of australia reveals the grenville aged crustal architecture a combination of upward continuation and the potential field tilt filter out magnetic anomalies relating to a late neoproterozoic orogenic event and emphasize the more subtle magnetic structural grain formed during the ca 1320 1150 ma musgravian orogeny the resulting images indicate that crustal architecture is defined by the distribution of ca 1150 ma magnetic granitoids within less magnetic basement and is dominantly northeast trending continuous beneath the amadeus and officer basins and defines an orogenic belt that connects mesoproterozoic provinces the orogenic belt is truncated within australia and precludes a direct east trending connection between the musgrave province and contemporaneous orogens in laurentia clockwise rotation of the south australian craton and subsequent collision with the north and west australian cratons is our preferred model to explain the grenville aged architecture observed in australia

mineralogy and petrology of a piemontite bearing schist western otago new zealand abstract pink piemontite spessartine bearing and grey green spessartine bearing manganiferous quartzose schists derived from siliceous pelagites and green quartzofeldspathic schists are described from the greenschist facies of the haast schist terrane near arrow junction western otago electron microprobe data are reported for sphene spessartine rich garnet manganoan epidote piemontite tourmaline phengitic muscovite chlorite albite haematite rutile manganoan calcite and chalcopyrite metamorphism occurred at about 6 4kbar 400 c xco2 was above the quartz rutile calcite sphene buffer xco2 0 02 throughout the recorded metamorphic history of the piemontite schists it dropped from above to below this critical buffering value in a spessartine rich schist and it was close to or below the buffering value in the quartzofeldspathic schists production of piemontite required high fo2 believed to be inherited from mnox in the parent pelagite substantial loss of o2 e g minimum of 0 19 by weight in one rock during diagenesis and or metamorphism is inferred in the grey green schists this inhibited piemontite formation slight loss of o2 and ca2 accompanied minor late stage replacement of piemontite by second generation spessartine observed zoning and mineral replacements indicate rise of temperature drop in pressure or invasion by solutions of lower fo2 and xco2 equilibrated with surrounding schists the detailed chemistry of the minerals studied correlates with available mn and with bulk rock fe3 x 100 fe2 fe3 the oxidation ratio ranges from 24 in average green quartzofeldspathic schist through 78 in average grey green manganiferous quartzose schist to almost 100 in some piemontite bearing schists as fe2 gives way to fe3 mg fe ratios tend to rise in chlorite phengite tourmaline spessartine and calcite mn increases and ti decreases in haematite mn increases in spessartine and calcite and fe increases in rutile available divalent cations are depleted relative to al chlorite is more aluminous and phengite more paragonitic than in typical haast schists

thermal history and differential exhumation across the eastern musgrave province south australia insights from low temperature thermochronology abstract multi method geo and thermochronological data obtained for palaeo and mesoproterozoic granitoids traversing the main structural architecture of the eastern musgrave province within south australia reveal multiphase cooling histories apatite u pb dating on six samples yield consistent ages of 1075 1025 ma suggesting a thermal reset coinciding with mantle derived magmatism of the greater warakurna large igneous province 1080 1040 ma apatite fission track aft analysis indicate that four discrete thermal events affected the study area inducing cooling through the aft partial annealing zone 60 120 c supported by apatite and zircon u th sm he data late neoproterozoic cooling from deep crustal levels to temperatures the results highlight a complex phanerozoic thermal history for the eastern musgraves and help to elucidate the poorly appreciated tectonic evolution of inland australia this study further demonstrates how high density sample transects across structural architecture can assess the relative crustal level and associated preservation of the thermal history record within fault reactivated terranes

the age of the ormiston pound granite implications for mesoproterozoic evolution of the arunta inlier central australia the ormiston pound granite southern arunta inlier intruded during the terminal stages late to post d2 of a major n directed overthrust event called the chewings orogeny which deformed supracrustal rocks of the simpsons and chewings assemblages ion probe zircon u pb analysis of the granite indicates an emplacement age of 1603 10 ma more than 500 ma older than the rb sr isochron age timing of emplacement is confirmed by an age of 1575 20 ma for zircon mantles from a gneissic xenolith in the granite zircon cores from the xenolith yield an age of 1678 14 ma which is taken to represent the protolith age of the surrounding gneisses the shrimp age is similar to but more precise than the 1586 69 ma rb sr isochron age for the chewings orogeny determined by marjoribanks and black 1975 penecontemporaneous 1600 ma magmatism is evident as pegmatites and associated fluid flow zones in the anmatjira and reynolds ranges northern arunta inlier 1100 1030 ma rb sr mica ages from the 1600 ma ormiston pound granite coeval pegmatites and 1680 ma host rock gneisses are similar to a sm nd isochron age for the mafic stuart dyke swarm of the southern arunta inlier and the contemporaneous alcarra dyke swarm in the musgrave inlier some 500 km farther south the rb sr mica ages reflect isotopic resetting by a thermal perturbation either associated with regional crustal extension during 1080 ma dyke intrusion or with the 1150 ma magmatic event in the southern arunta cf black and shaw 1992 irrespective the 1050 900 ma ormiston event described by shaw et al 1984 as granite intrusion associated with high grade metamorphism migmatization and folding needs to be re defined or abandoned

architecture and emplacement of the nebo babel gabbronorite hosted magmatic ni cu pge sulphide deposit west musgrave western australia the nebo babel ni cu platinum group element pge sulphide deposit in the west musgrave block western australia is the largest nickel sulphide discovery in the last 10 years the deposit is hosted within a concentrically zoned olivine free tube like chonolithic gabbronorite intrusion associated with the approximately 1 078 ma giles complex layered intrusions in the warakurna large igneous province emplaced into sulphide free amphibolite facies orthogneiss the fault offset nebo babel chonolith extends for 5 km and has a cross section of 1 0 5 km igneous mineralogy fabrics and textures are well preserved the lithostratigraphy includes variably textured leucogabbronorites vlgn that form an outer shell around mineralised gabbronorite mgn with barren gabbronorite bgn and oxide apatite gabbronorite oagn in the middle and lower parts of the chonolith mineral and whole rock geochemistry indicate that the units become progressively evolved in the order vlgn mgn bgn and oagn and that incompatible trace element concentrations increase downwards within the mgn and bgn the mineralisation which is confined to the early more primitive units vlgn and mgn occurs as massive sulphide breccias and stringers and as disseminated gabbronorite hosted sulphides the massive sulphides were emplaced late in the intrusive sequence have different pge chemistry and cu tenor to the disseminated sulphides and have undergone sulphide fractionation the distribution of disseminated sulphides which are primary magmatic in origin is related to chonolith geometry and magma flow regimes rather than to gravitational settling sulfur bearing country rocks are absent in the nebo babel deposit area and thus local crustal s addition was unlikely to have been the major mechanism in achieving sulphide immiscibility the nebo babel intrusion is part of an originally continuous magma chonolith with multiple and related magma pulses the parental magma was medium to low k tholeiite with 8 9 wt mgo the initial magma pulse vlgn the most primitive and sulphide saturated was probably emplaced along a linear weakness in the country rock after crystallisation of vlgn marginally more fractionated sulphide saturated magma was injected through the thermally insulated core of the conduit forming the mgn successive pulse s of more fractionated magma bgn were emplaced in the core of the intrusion after magma flow ceased closed system crystal fractionation produced consistent mineral and chemical fractionation trends within bgn and oagn after crystallisation the intrusion was overturned and then offset by the jameson fault resulting in the apparent reverse chemical and mineral trends in nebo babel

hydrogeochemistry and environmental isotopes of ground water in jeju volcanic island korea implications for nitrate contamination ground water from springs and public supply wells was investigated for hydrochemistry and environmental isotopes of 3h 18o and d in jeju volcanic island korea the wells are completed in a basaltic aquifer and the upper part of hydrovolcanic sedimentary formation nitrate contamination is conspicuous in the coastal area where most of the samples have nitrate concentrations well above 1 mg no3n l agricultural land use seems to have a strong influence on the distribution of nitrate in ground water comparison of stable isotopic compositions of precipitation and ground water show that ground water mostly originates from rainy season precipitation without significant secondary modification and that local recharge is dominant 3h concentration of ground water ranged from nearly zero to 5 tu and is poorly correlated with vertical location of well screens the occurrence of the 3h free old ground water is due to the presence of low permeability layers near the boundary of the basaltic aquifer and the hydrovolcanic sedimentary formation which significantly limits ground water flow from the upper basaltic aquifer the old ground water exhibited background level nitrate concentrations despite high nitrate loadings whereas young ground water had considerably higher nitrate concentrations this correlation of 3h and nitrate concentration may be ascribed to the history of fertilizer use that has increased dramatically since the early 1960s in the island this suggests that 3h can be used as a qualitative indicator for aquifer vulnerability to nitrate contamination copyright 2005 john wiley sons ltd

zircon u pb chronometry of the pressure and temperature history of granulites in the musgrave ranges central australia ion microprobe u pb measurements of zircon in the musgrave ranges of central australia date the emplacement of a charnockite which is cut by a shear zone containing a garnet clinopyroxene assemblage m2 pt conditions 11 kb and 720 c at 1200 ma veinlets of a post m2 adamellite cut an m4 assemblage pt conditions 6 kb and 670 c contained in a metadolerite inclusion suggesting that the adamellite was emplaced during or after m4 igneous and metamorphic zircons in the adamellite however grew at about 1200 ma indicating that m2 and m4 were synchronous at the level of precision of our data the time interval between the growth of the two assemblages can not have been more than 20 ma we interpret the pressure temperature and time ptt path obtained by combining our thermobarometric data and zircon u pb ages in terms of magmatic heat input in a thickened crustal segment followed by rapid possibly technically driven uplift of the lower part of the thickened crust to a depth of 15 20 km

duration of high pressure metamorphism and cooling during the intraplate petermann orogeny abstract the ediacaran cambrian petermann orogeny central australia is an exceptional example of intraplate orogenesis it involved sub eclogite facies metamorphism and extreme basin inversion during the exhumation of musgrave province basement from beneath the formerly contiguous centralian superbasin sensitive high resolution ion microprobe shrimp u pb geochronology of zircon titanite and rutile along with ti in zircon thermometry from meta igneous samples have been used to determine the timing and duration of high pressure metamorphism and subsequent cooling associated with this orogenic event peak metamorphic temperatures of 720 760 c were attained at 544 7 ma u pb zircon subsequent cooling to 600 660 c by 521 ma occurred at a rate of 2 6 7 0 c myr 1 as recorded by the closure of pb diffusion in titanite further cooling to 585 560 c by 498 472 ma occurred at a rate of 0 9 4 8 c myr 1 as recorded by pb closure in rutile the duration of tectonism was long lived 40 myr across the central and western parts of the orogenic system and deformation occurred in a comparatively warm and weak portion of crust characterised by regional thermal gradients of 17 26 c km 1 this proposed duration of tectonism is much longer than that permitted by a shear heating mechanism which requires an exceptionally short duration of tectonism and additionally an overall cold lithosphere characterised by geothermal gradients of 9 c km 1

intracratonic strike slip partitioned transpression and the formation and exhumation of eclogite facies rocks an example from the musgrave block central australia mountain belts developed in an intracratonic setting during the neoproterozoic in the center of australia mesoproterozoic granulite and amphibolite facies gneisses of the musgrave block were overprinted during the petermann orogeny 550 ma with zones of high strain concentrated along broadly east west trending shear zones these zones formed under eclogite facies t 650 c and p 12 kbars to greenschist facies conditions and may form part of a strike slip related crustal scale flower type structure granulite facies gneisses preserve ages older than 700 ma suggesting that these rocks did not experience temperatures greater than 350 c at 550 ma for these rocks not to have been thermally equilibrated to temperatures of 350 c at a depth of 12 kbars requires either an extraordinarily low geothermal gradient 9 c km 1 or if the geothermal gradient was more typical 20 c km 1 then transport to that depth and subsequent exhumation occurring in a short time interval 40 myr

occurrence and mobility of major and trace elements in groundwater from pristine volcanic aquifers in jeju island korea abstract major and trace elements in groundwater from basaltic aquifers in pristine conditions were investigated in a volcanic island to evaluate sources sinks and mobility of elements over a wide range of mineralization conditions with total dissolved solids from 50 mg l to 3400 mg l groundwater was highly undersaturated with respect to primary silicate minerals indicating that dissolution of basaltic rocks may continue under conditions with precipitation of calcite and secondary silicates evolution of b cl ratio in groundwater from marine aerosols to basaltic rocks showed that the ratio could be used as a conservative tracer for interactions between water and basaltic rocks relative mobility rm of elements calculated using the concentrations of elements in the local basaltic rocks and those in groundwater showed that mobility decreased in the order of b rb na k mg ca mo v si sr sc p u zn pb cr cu ba ni ti mn al fe co th indicating that oxyanion forming elements and alkali metals had the highest mobility compared to average rm v had decreased mobility and fe and mn had increased mobility in anoxic groundwater while v mo and u had higher mobility in oxic alkaline water the sources of v cr cu and zn in rocks were estimated using the partition coefficients between minerals and basaltic melt and the disparity between sources and mobility indicated that sinks are more important for controlling the concentrations of these elements in groundwater than the contents in the rocks principal component analysis pca of hydrogeochemical parameters in groundwater produced three principal components pc which represent dissolution of basaltic rocks without significant attenuation of released solutes higher degree of water rock interactions resulting in oxic alkaline conditions and attenuation of zn and cu in higher ph respectively spatial distribution of pcs revealed that groundwater with elevated concentrations of mobile elements was concentrated in the southwestern area and that concentrations of v and cr were more scattered which is likely to be controlled by ph and redox states of groundwater as well as degree of water rock interactions

evidence for shear heating musgrave block central australia the phenomenon of shear heating is generally difficult to recognise from petrologic evidence alone establishing that shear zones attain higher temperatures than the surrounding country rocks requires independent evidence for temperature gradients in the musgrave block central australia there is a clear spatial association between shear zones and interpreted elevated temperatures eclogite facies shear zones that formed at 550 ma record temperatures of 650 700 c outside the high pressure shear zones minerals with low closure temperatures such as biotite 450 c in the 40ar 39ar and rb sr systems preserve ages 800 ma suggesting that these rocks did not experience temperatures greater than about 450 c at 550 ma for any extended period thus the shear zones record temperatures that are 200 c higher than the surrounding country rocks simple calculations show that the combination of relatively high shear stresses 100 mpa and high strain rates 10 11 s 1 for short durations 1 ma can account for the observed apparent temperature variations the evidence indicates that shear heating is the dominant mechanism for localised temperature increases in the shear zones while the country rock remained at relatively lower temperatures

locating a major proterozoic crustal boundary beneath the eastern officer basin australia abstract the archaean to mesoproterozoic basement of northern south australia is almost completely overlain by thick neoproterozoic and younger basins 1 outcrop yet is likely to preserve an important record of the interactions between the archean proterozoic gawler craton and the proterozoic musgrave province during the amalgamation of australia in the proterozoic however constraints on the location and geometry of the boundary between these provinces are poor we use potential field data to determine the 3d basement architecture and so constrain where this palaeo mesoproterozoic boundary may be located beneath the eastern officer basin we establish the geometry and properties of the overlying basins and explicitly include them during forward and inverse modelling of potential field data to highlight the structure of the underlying basement our analysis identifies three crustal domains 1 southeast of the steep northeast southwest middle bore fault positive gravity and magnetic anomalies are co located and sourced from bodies in the upper crust these bodies overlie middle to lower crust that is apparently uniform 2 between the middle bore fault and the southern edge of the munyarai trough the highest amplitude gravity and magnetic anomalies are not co located and are sourced from large northwest dipping bodies 3 to the northwest the crust underlying the munyarai trough has similar properties to the musgrave province suggesting that the musgrave province extends at least 50 km beneath the eastern officer basin although details of the geology in the second central domain are poorly constrained the domain preserves large crustal scale precambrian structures and is interpreted to mark the boundary between the gawler craton and the musgrave province in particular the multiply reactivated middle bore fault forms a major crustal boundary and is interpreted to mark the northern limit of the gawler craton the middle bore fault may have formed as early as the kimban orogeny 1 7 ga although substantial reactivation and modification of the crustal architecture could have occurred between the kimban orogeny and intrusion of the cross cutting gairdner dolerite dykes 827 ma

post orogenic 1500 ma thermal history of the palaeo mesoproterozoic mt isa province ne australia abstract we present hornblende white mica biotite and alkali feldspar 40 ar 39 ar data from paleo mesoproterozoic rocks of the mt isa inlier australia which reveal a previously unrecognised post orogenic non linear cooling history of part of the northern australian craton plateau and total fusion 40 ar 39 ar ages range between 1500 and 767 ma and record increases in regional cooling rates of up to 4 c ma during 1440 1390 and 1260 1000 ma forward modelling of the alkali feldspar 40 ar 39 ar arrhenius parameters reveals subsequent increases in cooling rates during 600 400 ma the cooling episodes were driven by both erosional exhumation at average rates of 0 25 km ma and thermal relaxation following crustal heating and magmatic events early mesoproterozoic cooling is synchronous with exhumation and shearing in the arunta block and gawler craton late mesoproterozoic cooling could have either been driven by increased rates of exhumation or a result of thermal relaxation following a heat pulse that was synchronous with dyke emplacement in the arunta musgrave and mt isa province as well as grenville aged orogenesis in the albany fraser belt latest neoproterozoic cambrian cooling and exhumation was probably driven by the convergence of part of the east antarctic shield with the musgrave block and western australia petermann ranges orogeny as well as collisional tectonics that produced the delamerian ross orogen major changes in the stress field and geothermal gradients of the australian plate that are synchronous with the assembly and break up of parts of rodinia and gondwana resulted in shearing and repeated brittle reactivation of the mt isa inlier probably via the displacement of long lived basement faults within the northern australian craton

role of an impermeable layer in controlling groundwater chemistry in a basaltic aquifer beneath an agricultural field jeju island south korea abstract hydrochemical data major cations and anions and trace metals such as fe mn and v of groundwater n 144 were collected from 15 pre existing wells in the gosan area along the southwestern coast of jeju island south korea between january and october 2010 these were used to investigate the spatio temporal variability of groundwater quality in a basaltic aquifer beneath an agricultural field in the western part of the study area an impermeable clay rich layer gosan formation overlies the basaltic aquifer prohibiting direct recharge from rainwater infiltration and allowing a shallow perched aquifer to form above the formation robust principal component analysis robpca was performed to investigate the hydrochemical characteristics twenty seven outlying samples were separated from the total dataset among these 17 samples reflected seawater effects and seven samples reflected abnormally high impacts from agricultural contamination for the rest regular observations n 117 and a good leverage point robpca showed that principal component pc 1 effectively distinguishes uncontaminated water from those samples reflecting agricultural contamination variables with positive pc 1 loadings tds ca mg no 3 so 4 and cl indicate agricultural contamination while negative pc 1 loadings ph na k hco 3 and v possibly indicate basalt weathering samples with chemistry controlled by agricultural contamination are restricted to the eastern part of the study area while uncontaminated water is predominantly observed in the western part where the gosan formation occurs such a distinct spatial pattern indicates that overall groundwater quality is regulated by the occurrence of the impermeable formation groundwater samples from wells near the edge of the gosan formation show seasonal fluctuations in water quality with factor scores that indicates uncontaminated water in the dry season january to april and agricultural contamination in the wet season may to october this suggests that groundwater below the marginal part of the impermeable layer is seasonally contaminated by a temporal extension of the pollution front during the wet season even though the impermeable layer plays a role as a natural barrier to protect groundwater from the infiltration of surface contaminants this study also shows the advantage of robpca to successfully identify spatio temporal variation of groundwater quality in an area where diverse hydrochemical processes are coexisting and anormalous samples occur

stratigraphy petrochemistry and quaternary depositional record of the songaksan tuff ring jeju island korea abstract the songaksan tuff ring str is one of several recent hydrovolcanic centers on jeju island korea which provides an excellent example of proximal to distal facies changes in wet pyroclastic surge deposits a multidisciplinary study has been carried out on the str and adjacent lithostratigraphic units to constrain absolute age geochemical characteristics and quaternary depositional history a number of rock units were identified inside the crater of the str including scoria deposit i trachybasalt lava scoria deposit ii and a late stage basaltic tuff indicative of a rather complex sequence of magmatic and phreatomagmatic eruptions after the construction of the tuff ring petrochemical analysis shows that the str was generated from different magma batches that fractionated from a homogenous magma chamber and the early erupted magma was more evolved and volatile rich reworking of the str commenced shortly after the hydromagmatic eruption in a high energy nearshore environment resulting in deposition of the hamori formation the formation is composed of planar stratified and low to high angle cross stratified tuffaceous pebbly sandstones and occurs up to an altitude of about 4 m above present sea level 14c dating of molluscan shells beneath the formation indicates that it began to be deposited after about 4000 yr bp detailed sedimentary logging reveals that the formation consists of several stratal packages bounded by laterally persistent and distinct lithologic boundaries probably formed by millennial scale sea level fluctuations occurrence of another hydrovolcanic sequence the sinyangri formation on the opposite side of jeju island having similar sedimentary characteristics and ages suggests that the sea level fluctuations as seen in the hamori formation have affected a wide area of jeju island probably related to the high frequency sea level oscillations during the post 6 ka bp regression period in the east asian region it can be concluded that the formation of the str was possible because of the holocene transgression which made the present coastal areas water saturated and adequate for hydrovolcanic eruptions the str in turn contributed to record high frequency sea level fluctuations during the holocene via acting as a local and short lived but affluent source of loose sediment

relationships between deformation and basin evolution in the intracratonic amadeus basin central australia abstract tectonic subsidence curves based on the sedimentary record are used here to study basin evolution and to indicate deformational periods in the history of the intracratonic amadeus basin in central australia the basin developed during an initial period of extension at about 900 ma in the late proterozoic stage 1 was subjected to another period of extension at about proterozoic cambrian boundary time when there was also a shortening event on the southwest margin stage 2 and was shortened during the late devonian early carboniferous stage 3 stage 1 extension in the southwest and northwest corners of the basin was associated with rift basin sediments and volcanics previously regarded as basement to the amadeus succession in the metamorphic arunta complex on the northern margin of the basin a dolerite dyke swarm is considered to have been emplaced during this event extension in a n s direction associated with stage 2 occurred only in the northern part of the basin at the same time a major compressional event the petermann ranges orogeny was occurring along the southern margin in the north the sediment fill at this time firstly thickens rapidly towards the northern margin and then thins dramatically at the margin implying a half graben structure and the presence of a major bounding fault in the southwest the petermann ranges orogeny caused detachment of the sediments above the salt horizon in the bitter springs formation northward transport folding of the sediment pile and formation of major basement cored nappes during stage 3 a foreland basin associated with southward directed overthrust sheets of the alice springs orogeny formed in the northern part of the basin horizontal shortening was of the order of 50 100 km and hence the present basin margins are structural rather than depositional the structures that developed during this stage dominate the structural pattern of the basin

timing of plutonism in the proterozoic albany mobile belt southwestern australia abstract zircon u pb ages for two adamellites from the albany mobile belt in the albany fraser orogen of southwestern australia fall within the range 1174 12 ma and are interpreted as dating post tectonic granite emplacement in the belt slightly younger k ar ages on hornblendes from granulite and amphibolite facies metamorphic rocks from the southern part of the belt are interpreted as cooling ages recording uplift associated with the closing stages of orogeny and granite emplacement a u pb age of 1289 10 ma for zircons from an enderbitic gneiss adjacent to the 1177 12 ma old albany adamellite is interpreted as dating the emplacement of the granodioritic parent of the gneiss probably during granulite facies metamorphism this together with a previously reported rb sr age of 1300 ma for the granulite facies metamorphism in the northeast section of the albany fraser orogen suggests that granulite facies conditions were widespread in the orogen at 1300 ma previous sm nd results suggest that the granitoids were derived from 2000 ma old crust so far no older zircon xenocrysts which could support this model have been found in the granitoids

constraints on age erosion and uplift of neogene glacial deposits in the transantarctic mountains determined from in situ cosmogenic 10be and 26al 10 be and 26 al data from sandstone boulders in three neogene glacial deposits in the mcmurdo sound dry valleys region of southern victoria land antarctica indicate minimum exposure ages of approx 3 ma and maximum long term erosion rates of approx 5 12 cm m y supporting the suggestion that polar desert conditions have persisted in the dry valleys since at least late pliocene time variation of cosmogenic nuclide production rate with altitude also allows constraints on past uplift rates model calculations employing 10 be data indicate little or no uplift in the dry valleys region in the past 3 m y precluding rapid 1 km m y late pliocene uplift previously suggested for some parts of the transantarctic mountains

mineralogical association and ni co deportment in the wingellina oxide type laterite deposit western australia abstract the wingellina deposit currently owned by metals x limited is an oxide type ni co laterite with 168 mt of ore grading 0 98 ni and 0 08 co the laterite profile is derived from the weathering of the olivine rich mafic ultramafic layered intrusion of the giles complex mesoproterozoic and consists of a well developed limonitic ore and a thin saprolite horizon xrpd sem eds and empa analyses revealed that the ore zone is dominated by fe and mn hydr oxides which are the main carriers of both ni and co the mineralogy of the mn hydroxides is complex and high concentrations of co and ni occur mainly in a lithiophorite asbolane intermediate phase which has been subdivided into types i ii iii and iv with significant differences in their co ni ratios and al content the enrichment of metals in the lithiophorite asbolane phases is mainly controlled by the co and ni replacement of al in gibbsite like layers and rarely by ni incorporation in the vacancies of mn hydr oxides other less important metal bearing mn hydr oxides at wingellina include romanechite ernienickelite jianshuiite manganite and birnessite the texture and chemistry of the mn hydr oxides suggest that the lithiophorite asbolane phases were formed at a later stage with respect to the other manganiferous phases after repeated leaching and re precipitation of the mn hydr oxides this process could be one of the main factors controlling the enrichment of co and ni in the limonite zones during lateritization

the burning heart the proterozoic geology and geological evolution of the west musgrave region central australia the musgrave province is one of the most geodynamically significant of australia s proterozoic orogenic belts lying at the intersection of the continent s three cratonic elements the west north and south australian cratons while remoteness and cultural sensitivity have slowed geological research into this region recent collaborative programs in western australia the west musgrave province have done much to address this this focus review provides a synthesis of this and previous work investigating the mesoproterozoic to neoproterozoic geological evolution of the province the musgrave province is a mesoproterozoic to neoproterozoic belt dominated by granites formed and deformed during several major events a cryptic juvenile basement is exposed mainly in the east musgrave province as c 1600 1550 ma orthogneiss and in the west musgrave province as isolated outcrops of granulite facies metagranites of the c 1575 ma warlawurru supersuite zircon hf isotopic data suggest an earlier major juvenile crust forming event at c 1950 1900 ma there is however no evidence that the province evolved over archean crust the c 1600 1550 ma period probably involved evolution within a primitive arc setting perhaps developed on c 1950 1900 ma oceanic or oceanic arc crust voluminous calc alkaline plutonism was accompanied by clastic and volcaniclastic basin formation during the 1345 1293 ma mount west orogeny this stage traced the evolution of a continental arc reflecting the final amalgamation of the combined north and west australian craton with the south australian craton the intervening c 1400 ma primitive crust the madura province on which the proto musgrave province had evolved was consumed during amalgamation the thickened crust resulting from this accretion was drastically thinned at the beginning of the c 1220 1150 ma musgrave orogeny as this central part of the new combined craton entered an extraordinary period of high heat flow characterised by c 100 m y of ultrahigh temperature metamorphism and high temperature anhydrous alkali calcic magmatism sourced from mash chambers developed at the base of the thinned crust the ridged cratonic architecture and a massive accumulation of high radiogenic heat producing granites within the mid crust perpetuated a thin crustal regime voluminous magmatism was again triggered during the c 1090 1040 ma giles event with the evolution of the magmatism dominated ngaanyatjarra rift this event was likely initiated through renewed movement along translithospheric faults that intersected the thermally perturbed musgrave province pinned at a cratonic junction mantle derived bimodal magmatism extended more or less continuously for 50 m y producing one of the world s largest layered mafic intrusions and supervolcano sized additions of juvenile felsic crust in the form of alkali calcic to alkali a type rhyolite deposits together the albany fraser orogen which developed over the southern margin of the west australian craton and the musgrave province mark the preserved edge of the north and west australian craton these two belts show remarkable chronological links between c 1345 and 1150 ma but contrasting histories before and after that period their period of shared evolution reflects collision and accretion of the south australian craton but their tectonic setting and basement geology throughout that event were very different