copper mobility in the eastern creek volcanics mount isa australia evidence from laser ablation icp ms of iron titanium oxides the palaeoproterozoic eastern creek volcanics are a series of copper rich tholeiitic basalts which occur adjacent to the giant sediment hosted mount isa copper deposit in queensland australia the volcanic rocks are often cited as the source of metals for the deposit new laser ablation icp ms analyses of iron titanium oxides from the basalts provide evidence for the local mobilisation of copper during regional greenschist facies metamorphism this interpretation is based on the observation that copper bearing magmatic titanomagnetite was destabilised during greenschist facies metamorphism and the new magnetite which crystallised was copper poor petrological observations regional geochemical signatures and geochemical modelling suggest that the mobilised copper was concentrated in syn metamorphic epidote rich alteration zones creating a pre concentration of copper before the main mineralisation event at mount isa geochemical modelling demonstrates this process is enhanced by the addition of co2 from adjacent carbonate rich sediments during metamorphic devolatilisation regional geochemical data illustrate elevated copper concentrations in epidote rich zones high cao but where these zones are overprinted by potassic alteration high k2o copper is depleted a two stage model is proposed whereby after metamorphic copper enrichment in epidote titanite alteration zones an oxidised potassium rich fluid leached copper from the epidote altered metabasalts and deposited it in the overlying sedimentary rocks to form the mount isa copper deposit this ore forming fluid is expressed regionally as potassium feldspar rich veins and locally as biotite rich alteration which formed around major fluid conduits between the metabasalt metal source rocks and the overlying deposit host sequence this model is consistent with the remobilisation of copper from mafic source rocks as has been found at other world class copper deposits

localized surface disruptions observed by insar during strong earthquakes in java and hawai i abstract interferometric synthetic aperture radar data spanning strong earthquakes on the islands of java and hawai i in 2006 reveal patches of subsidence and incoherence indicative of localized ground failure interferograms spanning the 26 may 2006 java earthquake suggest an area of about 7 5 km 2 of subsidence 2 cm and incoherence south of the city of yogyakarta that correlates with significant damage to housing high modeled peak ground accelerations and poorly consolidated geologic deposits the subsidence and incoherence is inferred to be a result of intense shaking and or damage at least five subsidence patches on the west side of the island of hawai i ranging 0 3 2 2 km 2 in area and 3 8 cm in magnitude occurred as a result of a pair of strong earthquakes on 15 october 2006 although no felt reports or seismic data are available from the areas in hawai i the java example suggests that the subsidence patches indicate areas of amplified earthquake shaking surprisingly all subsidence areas in hawai i were limited to recent and supposedly stable lava flows and may reflect geological conditions not detectable at the surface in addition two a lava flows in hawai i were partially incoherent in interferograms spanning the earthquakes indicating surface disruption as a result of the earthquake shaking coearthquake incoherence of rubbly deposits like a flows should be explored as a potential indicator of earthquake intensity and past strong seismic activity

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

formation of lava tubes and extensive flow field during the 1991 1993 eruption of mount etna detailed mapping during the 1991 1993 eruption of mount etna has shown that there is a relationship between tumuli ephemeral vents lava tubes and their parent lava flows during this eruption many tubes formed in stationary inflated a a lava flows ephemeral vents at the fronts of these stationary flows and above lava tubes fed secondary lava flows many of which subsequently developed new tubes the resulting complex network of tubes ephemeral vents and secondary flows was responsible for most of the widening thickening and lengthening of the 1991 1993 etna lava flow field the supply of relatively uncooled lava via tubes to distal parts of this flow field allowed lava to flow 3 km farther from the vent than the longest channel fed lava flow our observations suggest that lava tubes play a more important role in the formation of extensive a a flow fields on etna than has previously been recognized

rheology of bubble bearing magmas the rheology of bubble bearing suspensions is investigated through a series of three dimensional boundary integral calculations in which the effects of bubble deformation volume fraction and shear rate are considered the behaviour of bubbles in viscous flows is characterized by the capillary number ca the ratio of viscous shear stresses that promote deformation to surface tension stresses that resist bubble deformation estimates of ca in natural lava flows are highly variable reflecting variations in shear rate and melt viscosity in the low capillary number limit e g in carbonatite flows bubbles remain spherical and may contribute greater shear stress to the suspension than in high capillary number flows in which bubble deformation is significant at higher ca deformed bubbles become aligned in the direction of flow and as a result contribute less shear stress to the suspension calculations indicate that the effective shear viscosity of bubbly suspensions at least for ca 0 5 is a weakly increasing function of volume fraction and that suspensions of bubbles are shear thinning field observations and qualitative arguments however suggest that for sufficiently large ca ca greater than about 1 the effective shear viscosity may be less than that of the suspending liquid bubbles reach their quasi steady deformed shapes after strains of order one for shorter times the continuous deformation of the bubbles results in continual changes of rheological properties in particular for small strains the effective shear viscosity of the suspension may be less than that of the liquid phase even for small ca results of this study may help explain previous experimental theoretical and field based observations regarding the effects of bubbles on flow rheology

shallow water and hypersaline features from the middle proterozoic mt isa sequence fundamental differences of opinion exist about the depositional environment of sediments which host the middle proterozoic1 mt isa cu and pb zn deposits2 3 of northwestern queensland australia the copper host has been repeatedly interpreted as an algal reef2 4 and recently as a sabkha5 whilst models as diverse as saline lakes6 and deep oceanic basins3 7 9 have been proposed for the deposition of both the cu and pb zn ore bodies we now report the discovery of stromatolites halite casts large cross bedded channel deposits and flat pebble conglomerates in sediments closely associated with the ore deposit these sedimentary structures provide evidence of shallow water deposition with intermittent hypersaline and emergent conditions during deposition of the upper mt isa group3 6 sequence the assemblage of sedimentary structures strongly supports a shallow marine or shallow lacustrine depositional model either model is inconsistent with the previously postulated red sea type submarine exhalative mineralization model3 7 9 for mt isa instead we argue that mt isa ore formation took place in a shallow water system possibly aided by the action of evaporite derived brines

seismic reflection imaging of mineral systems three case histories mineral deposits can be described in terms of their mineral systems i e fluid source migration pathway and trap source regions are difficult to recognize in seismic images many orebodies lie on or adjacent to major fault systems suggesting that the faults acted as fluid migration pathways through the crust large faults often have broad internal zones of deformation fabric which is anisotropic this coupled with the metasomatic effects of fluids moving along faults while they are active can make the faults seismically reflective for example major gold deposits in the archaean eastern goldfields province of western australia lie in the hanging wall block of regional scale faults that differ from other nearby faults by being highly reflective and penetrating to greater depths in the lower crust coupled thermal mechanical and fluid flow modeling supports the theory that these faults were fluid migration pathways from the lower to the upper crust strong reflections are also recorded from two

dynamic slip transfer from the denali to totschunda faults alaska testing theory for fault branching we analyze the observed dynamic slip transfer from the denali to totschunda faults during the mw 7 9 3 november 2002 denali fault earthquake alaska this study adopts the theory and methodology of poliakov et al 2002 and kame et al 2003 in which it was shown that the propensity of the rupture path to follow a fault branch is determined by the preexisting stress state branch angle and incoming rupture velocity at the branch location here we check that theory on the denalitotschunda rupture process using 2d numerical simulations of processes in the vicinity of the branch junction the maximum compression direction with respect to the strike of the denali fault near the junction has been estimated to range from approximately 73 to 80 we use the values of 70 and 80 in our numerical simulations the rupture velocity at branching is not well constrained but has been estimated to average about 0 8 cs throughout the event we use 0 6 cs 0 8 cs 0 9 cs and even 1 4 cs as parameters in our simulations we simulate slip transfer by a 2d elastodynamic boundary integral equation model of mode ii slip weakening rupture with self chosen path along the branched fault system all our simulations except for 70 and 0 9 cs predict that the rupture path branches off along the totschunda fault without continuation along the denali fault in that exceptional case there is also continuation of rupture along the denali fault at a speed slower than that along the totschunda fault and with smaller slip

paleomagnetic correlation of late quaternary lava flows in the lower east rift zone of kilauea volcano hawaii paleomagnetic data reflecting paleosecular variation psv of the geomagnetic field are used to correlate individual lava flows in the lower east rift zone of kilauea volcano this area has been recently mapped based on petrography stratigraphy soil development and degree of weathering of the flows eight 14c dates also provide a framework for the relative age assignments site mean directions of remanent magnetization for historic flows in this region indicate that local magnetic anomalies do not mask the psv signal that within flow angular differences are generally 5 and that temporal resolution of the paleomagnetic directions is of the order of 100 years the paleomagnetic correlations do not conflict with the observed stratigraphic relationships and psv reference curves from dated lava flows and lake sediments have also been used to help determine the sequence of directional groups paleomagnetic grouping of flows into eruptive events indicates a different and perhaps more refined eruptive history for the lower east rift zone than implied by the geologic mapping alone the number of individual flows based on petrographic distinctions is likely the same but the frequency of events including petrographically distinct flows is apparently lower than previously thought flows from ridge crest vents bifurcated by the rift indicate formation of the central graben in this region after 300 years ago possibly related to the 1790 eruptions along dual fractures

br cl geochemistry of hydrothermal brines associated with proterozoic metasediment hosted copper mineralization at mount isa northern australia abstract instrumental neutron activation analyses inaa of small bulk samples of vein quartz are used to estimate the br cl ratio of saline fluid inclusions associated with late metamorphic copper mineralization in quartz dolomite breccias at mount isa the results are compared with similar data from veins associated with district scale metasomatism in potential copper source rocks near mount isa and with quartz samples from other locations in northern australia which may have trapped fluids approaching the br cl composition of paleoproterozoic halite evaporites br cl ratios in some of the evaporite related samples are similar to present day seawater 0 0035 while others range up to 0 015 all samples from the mount isa copper ores fluids with total salinities mostly between 10 and 25 wt nacl eq have consistently high br cl ratios between 0 008 and 0 018 on average 3 5 times higher than modern seawater fluids associated with district scale alteration of metabasalts up to 30 km away from the deposit have high br cl ratios identical to those of the ore fluids this indicates a common source of the salts and supports a tentative correlation between mine and district scale alteration events and may ultimately help to trace potential fluid flow paths to or from the site of ore deposition the observed fluid compositions are contrary to the low br cl ratios that would be expected from a simple model of ascending fluids derived by prograde metamorphism of salt bearing paleoproterozoic metasediments mass balance calculations based on mine and district scale alteration suggest that the high br cl fluids may have originated above the present level of erosion as basin brines which infiltrated the terrain during the waning stages of regional metamorphism they may have formed in an inferred evaporitic cover sequence of mesoproterozoic age as residual bitterns or by diagenesis and partial dissolution of halite similar to modern br enriched basin brines secular variation in oceanic br cl preferential chlorine removal from evaporite derived metamorphic fluids by fluid rock interaction or an unusually br rich magma source beneath the deposit could provide alternative explanations for the high br cl ratios of the mount isa brines but are considered to be less likely processes in light of the available geologic data

tumulus development on lava flows insights from observations of active tumuli and analysis of formation models here we use observations of active flows along with detailed morphometric field measurements of more than 70 tumuli on flows at mount etna italy kilauea and hualalai us volcanoes to constrain a previously published model that estimates the pressure needed to form tumuli in an attempt to discover the nature and magnitude of pressure variations within active lava flow interiors we then consider how tumuli differ from idealized circular plates we incorporate observations of active tumuli and find that they may grow asymmetrically yet produce a symmetrical tumulus and can form where the flow path significantly changes direction bending models of clamped edges provide the most reasonable head estimates for the tumuli in our study tumulus formation requires the proper combination of cooling and effusion rate if cooling is too extensive and effusion rate too low the crust will provide too much resistance to bending if cooling is too limited and effusion rates too high crusts will not develop or have insufficient strength to resist fracture and subsequent breakouts we do not find it surprising that tumuli are rarely found over well established lava tubes that typically have rigid walls overlying crusts that exceed 2 m in thickness and provide too much resistance to bending silicic flows lack tumuli because the viscosity gradients within the flow are insufficient to concentrate stress in a localized area

origin of ultramafic xenoliths containing exsolved pyroxenes from hualalai volcano hawaii hualalai volcano hawaii is best known for the abundant and varied xenoliths included in the historic 1800 kaupulehu alkalic basalt flow xenoliths which range in composition from dunite to anorthosite are concentrated at 915 m elevation in the flow rare cumulate ultramafic xenoliths which include websterite olivine websterite wehrlite and clinopyroxenite display complex pyroxene exsolution textures that indicate slow cooling websterite olivine websterite and one wehrlite are spinel bearing orthopyroxene olivine cumulates with intercumulus clinopyroxene plagioclase two wehrlite samples and clinopyroxenite are spinel bearing olivine cumulates with intercumulus clinopyroxene orthopyroxene plagioclase two pyroxene geothermometry calculations based on reconstructed pyroxene compositions indicate that crystallization temperatures range from 1225 to 1350 c migration or unmixing of clinopyroxene and orthopyroxene stopped between 1045 and 1090 c comparisons of the abundance of k2o in plagioclase and the abundances of tio2 and fe2o3in spinel of xenoliths and mid ocean ridge basalt and a single 87sr 86sr determination indicate that these hualalai xenoliths are unrelated to mid ocean ridge basalt similarity between the crystallization sequence of these xenoliths and the experimental crystallization sequence of a hawaiian olivine tholeiite suggest that the parental magma of the xenoliths is hualalai tholeiitic basalt xenoliths probably crystallized between about 4 5 and 9 kb the 155 230 c of cooling which took place over about 120 ka the age of the youngest hualalai tholeiitic basalt yield maximum cooling rates of 1 3 10 3 1 91 10 3 c yr hualalai ultramafic xenoliths with exsolved pyroxenes crystallized from hualalai tholeiitic basalt and accumulated in a magma reservoir located between 13 and 28 km below sealevel we suspect that this reservoir occurs just below the base of the oceanic crust at about 19 km below sealevel

rhenium osmium systematics of the mount isa copper orebody and the eastern creek volcanics queensland australia implications for ore genesis the syn tectonic breccia hosted mount isa cu deposit in northwest queensland is the largest sediment hosted cu deposit in australia whole rock samples of chalcopyrite rich cu ore form an isochron with a re os age of 1 372 41 ma this age is more than 100 ma younger than the previously accepted age of cu ore formation an ar ar mineral age for biotite separated from the host rocks within the alteration envelope to the cu orebody this discrepancy cannot be unequivocally resolved due to a lack of other absolute geochronological constraints for cu mineralisation or the deformation event associated with cu emplacement the 1 372 41 ma date may reflect a the time of cu deposition b the time of a hydrothermal event that reset the re os signature of the cu ore or c mixing of the re os isotope systematics between the host rocks and cu bearing fluids however a range of published ar ar and rb sr dates for potassic alteration associated with cu mineralisation also records an event between 1 350 and 1 400 ma and these are consistent with the 1 372 ma re os age the 1 8 ga eastern creek volcanics are a series of tholeiitic basalts with a primary magmatic cu enrichment which occur adjacent to the mount isa cu deposit the whole rock os isotopic signature of the eastern creek volcanics ranges from mantle like values for the upper pickwick member to more radiogenic crustal values for the lower cromwell member the re os isotope signature of the cu ores overlaps with those calculated for the two volcanic members at 1 372 ma hence the os isotope data are supportive of the concept that the os in the cu ores was sourced from the eastern creek volcanics by inference it is therefore postulated that the eastern creek volcanics are the source of cu in the mount isa deposit as both os and cu are readily transported by oxidised hydrothermal fluids such as those that are thought to have formed the cu orebody the pickwick member yields a re os isochron age of 1 833 51 ma which is within error of previously reported age constraints the initial 187os 188os isotopic ratio of 0 114 0 067 os 0 7 is slightly subchondritic and together with other trace element geochemical constraints is consistent with a subcontinental lithospheric mantle source the pickwick member records a minimum age of ca 1 95 ga for melt depletion in the subcontinental lithospheric mantle beneath the mount isa inlier prior to the extraction of the magmas which formed the eastern creek volcanics this corresponds with the end of subduction related magmatism along the eastern margin of the northern australian craton which included the mount isa inlier

methods of determining the rheological properties of magmas at sub liquidus temperatures non vesicular basaltic melts behave as newtonian fluids at temperatures above their liquidus and their viscosities can be calculated using a method developed by shaw 1972 and bottinga and weill 1972 because many igneous processes involve the flow of silicates at sub liquidus temperatures numerous attempts have been made to calculate the interactive effects of the crystal phase however current methods are appropriate only for relatively low crystal concentrations and they assume newtonian behaviour we argue that this assumption is invalid when bubble or crystal concentrations exceed 30 at higher concentrations factors other than concentration become increasingly important these include particle shape and size distribution a method which takes these factors into account is tested on a range of suspensions including magmas at sub liquidus temperatures and rheological properties calculated using this method agree closely with the measured values we also demonstrate that an equation which was introduced to explain large differences in measured apparent viscosities during the cooling and crystallisation of mount st helens dacite murase et al 1985 and which is currently used to calculate the rheological properties of crystallising lavas generates viscosities which may be in error by several orders of magnitude this difference is argued to be caused by a combination of factors including the ten orders of magnitude range in the strain rates utilised during the mount st helens measurements causing orders of magnitude difference in the resulting apparent viscosities rheological data on crystallising silicic melts are reinterpreted taking into account the non newtonian rheology of the magmas and changes in activation energy of flow during crystallisation

uranium deposits of the mount isa region and their relationship to deformation metamorphism and copper deposition the mount isa region contains over 20 uranium deposits few of which contain economic concentrations of uranium they are thought to be significant in the exploration for new copper deposits based on the model that the uranium deposits are located in the pathways of oxidized hydrothermal fluids that formed the postmetamorphic mount isa copper orebodies there are two uranium deposit types both hosted in volcanosedimentary rocks we suggest that they represent one mineralization event but different metamorphic histories examples in the eastern low grade metamorphic zone are dominated by a brannerite anatase apatite assemblage and are low in uranium the examples in the western high grade metamorphic zone are characterized by uraninite and titanite with higher uranium concentrations the chemical association of u ti and ca is consistent for all deposits however phosphate is only important at low metamorphic grade the most likely mechanism of formation in the lower metamorphic grade anderson s lode example is the complete replacement of chlorite in the sedimentary host rock matrix by the mineralizing assemblage in this model chlorite acted as a reductant allowing the deposition of uranium from an oxidized fluid this mechanism of uranium deposition is similar to that proposed for unconformity type uranium deposits we conclude that these uranium deposits are metamorphosed equivalents of proterozoic unconformity type uranium deposits found elsewhere in northern australia at anderson s lode brannerite and apatite were concentrated in veinlets by pressure dissolution after the deposition of the original assemblage these pressure dissolution seams are cut by premetamorphic quartz chlorite veins examples at higher metamorphic grade have textures that suggest uranium deposition was pre to synmetamorphic at the latest this precludes any genetic or temporal connection between the uranium deposits and the postmetamorphic mount isa copper deposit

volcanism in aboriginal australian oral traditions ethnographic evidence from the newer volcanics province abstract this article collects and presents nineteenth century ethnographic evidence from the newer volcanics province of australia and explores how volcanism was recorded and understood in aboriginal oral traditions it investigates whether aboriginal australian oral traditions can be understood as persistent eyewitness accounts of volcanic eruptions in the newer volcanics province how and what kind of geological and volcanological knowledge was embedded within aboriginal australian oral traditions and considers what value the ethnographic evidence has for understanding both the socio cultural and geological histories of the newer volcanics province

a 3 d geological and structural synthesis of the leinster area of the agnew wiluna belt yilgarn craton western australia with special reference to the volcanological setting of komatiite associated nickel sulfide deposits the leinster area is situated toward the southern end of the agnew wiluna belt in the yilgarn craton of western australia and hosts the giant perseverance komatiite associated nickel sulfide deposit at in excess of 1 2 mt contained ni this is the biggest type 1 basal sulfide rich accumulation deposit in the world and it is associated with a number of smaller deposits that extend over a strike length of 20 km adjacent to the perseverance fault on the eastern margin of the belt in broad terms the greenstone sequence comprises an eastern rift proximal komatiite dacite sequence and a western and more marginal basalt dominated sequence with minor komatiite the komatiites display a wide range of compositions and textures from highly magnesian olivine meso to adcumulate rocks composed of olivine with forsterite contents of up to 94 5 to sequences of thin spinifex textured komatiite flow units this compositional range indicates considerable variation in volcanic facies from rift proximal to distal loci of focused flow termed pathways indicated by thickened cord like bodies of more olivine rich rock occur at all scales and are intimately associated with the ni sulfide mineralization the pathways are linked by thinner sequences of lower mgo rocks either layered olivine orthocumulate rocks or sequences of thin spinifex textured flow units some of the lower mgo komatiite sequences appear to emanate from the tops of pathways in the manner of breakout flows in tube fed basaltic terrains variably sulfidic black shales and cherts and barren exhalative iron sulfide horizons are intimately interlayered with the komatiitic rocks the overprinting effects of regional deformation and metamorphism spanning at least 80 m y are considerable at least eight local deformation events have been recognized by previous workers these have been used to constrain the 3 d model and can be linked to craton wide structural schemes some of the major faults are clearly accretionary and reflect reactivation of underlying basin forming structures early north over south thrusting was followed by e w directed basin closure and the development of nnw trending open regional folds extension accompanied batholithic granitoid intrusion and reactivated rift parallel nnw trending faults producing the major strike slip fault systems that divide the greenstone succession into a series of structural and stratigraphic domains the ensuing orogenic collapse resulted in overturning of the stratigraphy to the east subsequent brittle deformation events have produced fault sets in a variety of orientations that can be related to ongoing shortening with a variable principal stress orientation there is a complex interplay of structural and volcanological controls on the formation and subsequent deformation of the ni sulfide deposits in this ancient terrane three dimensional modeling has furthered a detailed understanding of the geologic and structural evolution of the belt allowed the identification of komatiite pathway positions and their plunges and provided quantitative data on the magnitude and direction of fault offsets of different generations the modeling exercise has shown that it is possible to strip away the effects of overprinting metamorphism and deformation to reveal some of the primary controls on komatiite volcanism and the location of ni sulfide deposits even in those portions of greenstone belts that are highly deformed and have undergone amphibolite facies metamorphism this is illustrated with case studies of the perseverance venus rocky s reward harmony and sir lancelot deposits three dimensional modeling has the capacity to integrate geologic geochemical and geophysical datasets in a way that fully utilizes the results of past exploration programs and produces a premium geologic product that can be used to guide further exploration the recent discovery of the venus deposit is in part a tribute to the power of this approach

a shortened intraplate rift system in the proterozoic mount isa terrane nw queensland australia the leichhardt river fault trough of the mount isa terrane developed a complex extensional architecture between approximately 1800 and 1600 ma forming the underlying template upon which compressional structures were superimposed during the 1590 to 1500 ma isan orogeny basin fill material accumulated during at least five multiphase periods of rifting and associated postrift subsidence forming a stacked succession of unconformity bounded sequences initial e w extension was associated with a massive magmatic event half graben greater than 50 km in width and of alternating asymmetry localized the extrusion of up to 4 km of continental tholeiites thereafter a period of n s extension resulted in southward tapering north tilted half graben in which synrift basaltic and siliciclastic strata accumulated n s extension was followed by regional postrift subsidence and the deposition of a laterally continuous quartzite carbonate package a multiphase period of e w to nw se extension ensued during which time two unconformity bounded sequences accumulated the stratal architectures of these sequences are strongly asymmetric in cross section exhibiting a pronounced rotational thickening toward the east consistent with their deposition in the hanging walls of east dipping tilt blocks between 15 and 40 km in width finally a period of n s extension resulted in the development of e w trending f1 drag synclines in the highest level cover rocks the association of angular unconformities and block bounding faults e w trending synclines and e w striking faults and the unique internal fold geometries of fault blocks suggest that many fault bounded blocks originated as coherent structural entities during rifting and continued to act as such during subsequent shortening

an igneous origin for features of a candidate crater lake system in western memnonia mars the association of channels inner terraces and delta like features with martian impact craters has previously been interpreted as evidence in favor of the past existence of crater lakes on mars however examination of a candidate crater lake system in western memnonia suggests instead that its features may have formed through igneous processes involving the flow and ponding of lava accumulations of material in craters and other topographic lows throughout much of the study region have characteristics consistent with those of volcanic deposits and terraces found along the inner flanks of some of these craters are interpreted as having formed through drainage or subsidence of volcanic materials channels previously identified as inlets and outlets of the crater lake system are interpreted instead as volcanic rilles these results challenge previous interpretations of terrace and channel features in the study region and suggest that candidate crater lakes located elsewhere should be reexamined

the geochemical environment of the wilcherry hill base metal mineralisation south australia high grade lead zinc silver mineralisation occurs in metamorphosed carbonate and calc silicate sequences at wilcherry hill south australia whole rock lithogeochemistry indicates that the host sequence of the mineralisation can be defined and contrasted from others at both prospect and exploration licence scales geochemical haloes are identified on the basis of pb zn and mn variations a saline and possibly evaporitic environment of deposition distal from basin margins is proposed for the host sequence on the basis of alkali element compositions iron formation facies carbonate compositions and comparisons with geochemically similar less metamorphosed sequences with base metal mineralisation in the middle proterozoic of northern australia the combination of geochemical haloes and definition of the depositional environment provide additional criteria for the exploration geologist even in metamorphosed and deformed terrains

emplacement of the most recent lava flows on hualālai volcano hawai i a detailed field and petrologic study of the ca 1800 a d flows at hual lai volcano documents at least two eruptive episodes the hu ehu e flow field ending in 1801 and the ka p lehu flow several decades earlier the morphology and stratigraphy of the ka p lehu flow require an emplacement duration of several days to weeks based on a comparison with recent eruptive activity at mauna loa volcano the eruption cannot have occurred at the anomalously high rate 104 105 m3 s proposed by previous workers the hummocky flow surface of the later phase of the hu ehu e eruption suggests a duration of months based on a comparison with recent eruptive activity at k lauea volcano although none of the ca 1800 flows show evidence for extraordinarily fast emplacement or unusual fluid rheologies both flows show unusual features the abundant xenoliths for which the ka p lehu flow is famous were transported in numerous episodes of deposition and remobilization during which they eroded the channel systems through which they traveled lava transport in proximal and medial regions of both flow fields was probably through lava tubes as evidenced by preserved tubes and by the prevalence of p hoehoe lined channels that require thermally efficient transport of lava over great distances both flows also show abundant evidence for re occupation of older cones and lava tubes a characteristic that may typify infrequent eruptions of older volcanic systems although lava flows from hual lai volcano do not show anomalous eruptive behavior they pose a substantial hazard for coastal communities of kona

morphometric analysis of lava flow units case study over lidar derived topography at mount etna italy abstract high resolution lidar derived digital elevation models of volcanic areas can significantly improve knowledge of lava flow morphology and emplacement mechanisms here we focus on single flow units presenting a new semi automatic procedure which provides a quantitative analysis of their shape the method relies on the automatic processing of the elevation profiles obtained on transects orthogonal to the flow unit axis the initial phase of the mount etna flank eruption from september 2004 is taken as test case and the procedure is applied on an active lava flow which was emplaced on the eastern flank of the volcano the main topographic dataset used is a 2 m resolution digital elevation model obtained from a lidar survey starting from the axis of a lava flow unit our method yields morphometric data on the flow unit at a 2 m spacing calculating parameters including flow width channel width the heights of the levees inward and outward slope of levees and estimating pre emplacement slope along the axis the procedure is embedded in a customized gis which allows easy processing handling and displaying of data the procedure has also been applied to another flow unit emplaced during the october november 1999 overflow from the bocca nuova crater results show that the channel width seems to accommodate first order trends of the pre emplacement slope along the flow unit axis while it is little affected by high frequency changes in slope in contrast flow unit width and flow unit thickness are apparently influenced by small scale changes in slope the different emplacement conditions of the two flow units are reflected by the overall contrasting morphologies as shown by the different average thickness and by the different ratios between i flow width vs channel width and ii flow unit section area vs channel width the new method provides an enhanced systematic and thorough morphometric description of flow units which may improve the understanding of the emplacement mechanisms of lava flows on earth and other planets

welcoming a monster to the world myths oral tradition and modern societal response to volcanic disasters abstract volcanic eruptions can overwhelm all senses of observers in their violence spectacle and sheer incredibility when an eruption is catastrophic or unexpected neither individuals nor communities can easily assimilate the event into their world view psychological studies of disaster aftermaths have shown that trauma can shake the very foundations of a person s faith and trigger a search supernatural religious or scientific for answers for this reason the ability to rapidly comprehend a traumatic event by accepting the catastrophe as part the observer s world represents an important component of community resilience to natural hazards a relationship with the event may be constructed by adapting existing cosmological ancestral or scientific frameworks as well as through creative and artistic expression in non literate societies communal perceptions of an event may be transformed into stories that offer myth like explanations as these stories make their way into oral traditions they often undergo major changes to allow transmission through generations and in some cases to serve political or religious purposes disaster responses in literate societies are no different except that they are more easily recorded and therefore are less prone to change over time here we explore ways in which the language imagery and metaphor used to describe volcanic events may link disparate societies both present and past in their search for understanding of volcanic catastrophes responses to modern eruptions 1980 mount st helens usa and 1995 present soufriere hills montserrat provide a baseline for examining the progression to older historic events that have already developed oral traditions 1886 tarawera new zealand and finally to oral traditions many hundreds of years old in both the pacific northwest us and new zealand nz we see that repeated volcanism over many generations produces rich webs of cosmology and history surrounding volcanoes nz maori have incorporated volcanoes into the lineage of tribes and individuals thus good and bad outcomes from volcanism are part of long term cycles of reciprocity and equilibrium that link modern maori to their ancestors in both regions cosmologies and mythologies not only document the attempts of past cultures to recover from the impacts of volcanic disasters but also provide a means by which following generations can understand contextualize and therefore recover from future volcanic catastrophes we further suggest that such local traditions can provide a valuable community education tool as well as an important means of aiding the psychosocial recovery of individuals and communities after volcanic disasters

b_na rich palaeoproterozoic aravalli metasediments of evaporitic association nw india a new repository of gold mineralization we report field observations and preliminary petrochemical and stable isotopic compositions of the host rock and sulfide minerals for a recently discovered sulfide hosted gold deposit from the palaeoproterozoic aravalli rocks in northwestern india gold occurs associated with feascu co sulfides in lithofacies of diverse mineralogical composition dominated by amphibole bearing dolomitic marble and albite rich quartzo feldspathic rocks qfr the presence of vugs believed to be after dissolution of halite patches coupled with the development of scapolite bearing assemblages in dolomite marble occurrence of tourmaline rich mineralized rocks and very high na content of carbonates and qfr indicate hypersaline depositional environment for the host rock a narrow spread of 34 scdt values from 10 5 to 12 8 for stratiform arsenopyrite and remobilized pyrrhotite corroborates hypersaline to evaporitic depositional environment the 13 c values for gold bearing carbonates show bimodal distribution one population mean 0 4 v pdb is close to the sea water carbonate values while the other 3 l indicates probable mantle affinity the 18 o values for carbonates mean 18 4 v smow are not discriminative as they appear to have been modified by subsequent metamorphism and hydrothermal activity interpretation of mantellic source for carbon is borne out from the absence of biogenic activity and incompatibility of significantly negative 13 c values in the evaporitic setting of deposition of bhukia rocks we suggest that nab rich fluids channeled through rift related faults were responsible for creating hypersaline conditions that eventually evolved into an evaporitic environment mantle carbon through some still deeper faults was probably responsible for the gold transport and its subsequent deposition in an otherwise uncommon evaporitic repository of carbonates and qfr 2002 elsevier science b v all rights reserved

dynamics of a confined lava flow on kilauea volcano hawaii this paper presents a new method of analysing lava flow deposits which allows the velocity discharge rate and rheological properties of channelled moving lavas to be calculated the theory is applied to a lava flow which was erupted on kilauea in july 1974 this flow came from a line of fissures on the edge of the caldera and was confined to a pre existing gully within 50 m of leaving the vent the lava drained onto the floor of the caldera when the activity stopped but left wall and floor deposits which showed that the lava banked up as it flowed around each of the bends field surveys established the radius of curvature of each bend and the associated lava levels and these data together with related field and laboratory measurements are used to study the rheology of the lava the results show the flow to have been fast moving but still laminar with a mean velocity of just over 8 m s 1 the lava had a low or negligible yield strength and viscosities in the range 85 140 pa s an extension of the basic method is considered and the possibility of supercritical flow discussed

saline pan deposits from the 1 8 ga makgabeng formation waterberg group south africa abstract interbedded medium to fine grained sandstones and mudstones which occur within an 800 m thick areally extensive aeolian dune and interdune deposit of the 1 8 ga makgabeng formation waterberg group south africa are interpreted as saline pan deposits few examples of saline pan deposits have been documented from the precambrian rock record most of those described have been assigned to alkaline saline and playa lake settings seven saline pan facies are recognized in the makgabeng formation a strongly asymmetrical ripples b inversely graded laminations c slightly asymmetrical ripples d symmetrical ripples e massive sandstone f horizontal lamination and g massive graded mudstone these facies are interpreted respectively as current ripple wind ripple combined flow ripple wave ripple suspension e and g and upper plane bed deposits f xrd analysis of saline pan mudstones from drill core south of the study area indicates the presence of trace amounts of anhydrite and gypsum additional evidence for evaporite deposition includes evaporite pseudomorphs in the underlying dune deposits and distinctive structures linked to efflorescent salt crust development stacking of facies reflects fluctuations 10 s to 100 s of years in the hydrologic regime of the saline pan whereas the efflorescent crusts are consistent with shorter period months or years flooding and desiccation cycles maximum saline pan depths and geographic extent are recorded by thick graded mudstone facies g near the base of the deposit indicating a time of possible climatic amelioration and saline pan expansion followed by semiarid to arid conditions reflected in the overlying dune deposits

vesiculation of basaltic magma during eruption vesicle size distributions in vent lavas from the pu9u9o9o kupaianaha eruption of kilauea volcano are used to estimate nucleation and growth rates of h 2 o rich gas bubbles in basaltic magma nearing the earth9s surface 120 m depth by using well constrained estimates for the depth of volatile exsolution and magma ascent rate nucleation rates of 35 9 events cm 3 s 1 and growth rates of 3 2 x 10 4 cm s are determined directly from size distribution data the results are consistent with diffusion controlled growth as predicted by a parabolic growth law this empirical approach is not subject to the limitations inherent in classical nucleation and growth theory and provides the first direct measurement of vesiculation kinetics in natural settings in addition perturbations in the measured size distributions are used to examine bubble escape accumulation and coalescence prior to the eruption of magma

geodynamic evolution of the proterozoic mount isa terrain the proterozoic mount isa terrain records the effects of four periods of intraplate tectonism the c 1870 ma barramundi orogeny was characterized by a massive felsic magmatic event and global correlations suggest a physical link between australia and laurentia at this time thereafter the terrain underwent an extensional history spanning 200 ma involving repeated episoded of rifting post rift subsidence and associated depositional and magmatic phases this protracted rifting history resulted in a cumulative stratigraphic thickness of up to 25km above attenuated continental crust rifting was interrupted prior to the formation of ocean crust by the compressional isan orogeny 1590 1500 ma the isan orogeny was synchronous with low pressure high temperature metamorphism and widespread metasomatism in the waning stages of shortening the mount isa terrain evolved into a wrench system characterized by an extensive network of strike slip faults the current level of exposure in this terrain provides spectacular examples of superimposed rifts basin inversion and wrench geometries developed at middle to upper crustal levels

chemical and stable isotopic characteristics of syn tectonic tourmaline from the western fold belt mount isa inlier queensland australia abstract understanding hydrothermal fluid flow events related to orogenic events is important because they provide large scale redistribution of metals which may become concentrated in ore deposits in this study we determine the origin of tourmaline bearing quartz veins and pegmatites in the western fold belt of the proterozoic mount isa inlier a region which host numerous syn orogenic cu deposits this paper uses tourmaline mineral chemistry and isotopic analyses in situ b and bulk o and h isotopes to fingerprint the fluid reservoirs that contributed to the fluid budget during the isan orogeny all the tourmaline samples have schorl dravite solid solution compositions quartz tourmaline 18 o 11 0 12 6 and 7 7 9 4 v smow respectively pairs yield equilibrium formation temperatures of 305 to 575 c with the higher temperatures related to pegmatitic tourmaline tourmaline d values have a relatively narrow range from 68 to 56 v smow in most cases calculated 18 o fluid and d fluid values are compatible with primary magmatic water with a small component of metamorphic 18 o enriched formation waters however there are large variations in tourmaline 11 b values which range from 10 7 to 17 0 with the majority of values between 10 and 15 variations in 11 b tur in the pegmatites suggest that boron degassing generated relative 11 b depletion during crystallization similar 11 b tur values in quartz tourmaline veins spatially associated with the pegmatites in cordierite and sillimanite bearing metamorphic rocks west of the mount isa fault demonstrate a similar origin for b in this tourmaline in contrast quartz tourmaline veins of similar timing hosted by greenschist grade metamorphic rocks east of the mount isa fault have much higher 11 b tur values 6 2 to 10 7 which reflect the involvement of a distinct b isotopic reservoir mostly likely a near surface derived evaporitic brine thus the b isotopic data reveal important differences in fluid origin that are not reflected in the 18 o values therefore at least two isotopically distinct fluids one sourced from fractionating anatectic pegmatites and the other from external basinal brines circulated contemporaneously in separate areas during the isan orogeny there is no evidence based on the tourmaline isotopic data to suggest that these fluids mixed which demonstrates that the hydrothermal plumbing system in the western fold belt during the isan orogeny was disconnected probably due to differences in thermal structure metamorphic grade across the western fold belt during orogenesis

an early soda ocean in analogy to modern soda lakes commonly associated with volcanic regions it is postulated that the ancient sea had a high alkalinity a high ph and low ca and mg concentrations the change towards nacl dominance as observed in the present day ocean can best be explained by a series of mineral equilibria crustal differentiation and life processes in principle hydrothermal leaching of chlorine from the oceanic crust caused this ion to accumulate in the sea while at the same time dissolved carbonates became gradually removed by organisms and carbonates the switch from a soda to a halite ocean was accomplished 1 ga ago critical biochemical events marking the chemical evolution of the precambrian sea and their implications for the pco2 in air will be discussed

sedimentology and geochemistry of a mid proterozoic lacustrine unit from northern australia abstract the wollogorang formation is an unmetamorphosed middle proterozoic sedimentary unit ca 100 m thick in the highly mineralized mcarthur basin of northern australia based on sedimentology three of the six lithofacies in this unit can be confidently interpreted to be of continental origin facies 1 evaporitic red beds deposited in highly saline mudflats on an irregular volcanic landsurface at the base of the formation facies 3 varved organic rich black shales deposited in a quiet water distal lacustrine setting in the middle of the formation and facies 5 conglomeratic cross bedded poorly sorted dolomitic sandstones deposited in braided fluvial environments near the top of the formation a detailed geochemical study mainly of facies 3 was carried out to see if the two studies would complement each other and to show what geochemical criteria may be useful in defining proterozoic depositional environments dolomite concretions which are present in the carbonate poor black shales of facies 3 are shown to be early diagenetic the 87 sr 86 sr ratio from one of these concretions is 0 7139 significantly above the accepted range for marine carbonates of this age 0 705 0 708 these concretions and surrounding black shales often contain relatively high pyrite contents the concretions have 13 c values similar to the average host dolomite value of 0 6 and pyrite 34 values range from 3 5 to 5 8 c av 2 4 0 these data agree with the sedimentology and indicate a low sulfate lacustrine environment with little activity from the sulfate reducing bacteria disseminated pyrite 34 s values from facies 2 and 4 up to 11 8 0 suggest similar low sulfate environments this combined with carbonate 18 o values of around 23 facies 1 4 suggests there was only one water source present during deposition diagenesis and lithification when these data are viewed in the light of the regional stratigraphic setting and the gradational facies relationships they suggest a non marine setting for the bulk of the wollogorang formation and support previous observations of an abundance of rift related continental environments in this highly mineralized region the relatively high pyrite s organic c ratios found during this study are interpreted as indicating some addition of hydrothermally formed pyrite this result is similar to that found in the black shales from the younger more highly mineralized rocks of the mcarthur basin and may support the originally perceived mineral ootential of units such as the wollogorang formation jackson 1981a

lithogeochemical exploration for shale hosted lead zinc deposits case studies from the mcarthur river and mt isa districts northern australia the large lead zinc deposits of middle proterozoic age in northern australia occur in sediments interpreted as having been deposited under saline shallow emergent conditions significant alkaline diagenesis is evident from the presence of abundant k feldspar and locally albite alkali element compositions clearly distinguish the sediments of the mineralised shallow emergent locations both from those of more permanent water cover lacustrine or lagoonal and from those close to basin margins the key variables for identifying the geochemical contrasts are the levels of k rb and na and the ratios of k al and k rb these geochemical parameters can be used in conjunction with the levels of the target and indicator elements to detect whether mineralisation may be present in a favourable geological environment two case studies of the application of whole rock geochemistry in base metal exploration are given for the glyde river sub basin mcarthur basin and the western succession mt isa block

asymmetric extension of the middle proterozoic lithosphere mount isa terrane queensland australia abstract the middle proterozoic mount isa basin of the mount isa terrane hosts several large pb zn ag deposits and is arguably one of the richest mineral provinces in the world the deformed remnants of this basin extend from the eastern margin of the leichhardt river fault trough through to the murphy tectonic ridge in the far north of the terrane the mount isa basin initially evolved in response to nw se directed extension during the mount isa rift event this event began before 1708 ma and had ceased by 1653 ma a sag basin continued to evolve thereafter until 1595 ma regional analysis of the highest level cover rocks of the mount isa basin reveals a notable difference in the locus of syn rift sedimentation syn rift magmatism and post rift subsidence although crustal extension was widespread across the mount isa basin tectonic subsidence was focussed along the n s oriented mount isa rift approximately 3 5 km of fluvial to shallow marine clastic sediments were deposited into isolated rift basins bimodal volcanism and emplacement of shallow level plutons occurred along the western and northwestern margins of the mount isa rift magmatic provinces mark the locus of significant subcrustal lithospheric thinning asthenospheric upwelling and mafic underplating within these magmatic provinces the syn rift sequences are fewer and thinner 750 2000 m and were dominantly deposited in subaerial environments suggesting a relatively stable uplift and subsidence history the position of maximum subcrustal lithospheric extension is determined by the position of greatest post rift subsidence this occurred beneath the northern mount isa terrane where the thickest post rift sequences are preserved and the depositional history is more protracted we propose that the evolution of the mount isa basin is a consequence of asymmetric extension of the middle proterozoic lithosphere

meta evaporite sequence exhalative chemical sediments and associated rocks in the proterozoic willyama supergroup south australia implications for metallogenesis abstract the willyama supergroup comprises proterozoic meta sedimentary and meta igneous rocks in western new south wales and eastern south australia and contains the giant broken hill pb zn ag deposit in addition to numerous small stratiform stratabound and vein mineral deposits new lithological geochemical and fluid inclusion data from the olary block west of broken hill suggest the presence of former evaporite rocks now metamorphosed to a variety of chemically and mineralogically unusual lithologies these evaporite rocks overlie relatively oxidised strata and are in turn overlain by reduced graphite bearing pelites rocks of sodic composition abound represented by albite quartz rich rocks calcite actinolite epidote garnet clinopyroxene inferred to represent metamorphosed analcime rich strata of felsic volcaniclastic provenance with variable proportions of carbonates for example calcite dolomite trona and shortite these rocks are interspersed with potassic rocks possibly also with an evaporitic origin in addition to normal clastic meta sediments the presence of halogen rich minerals in a distinctive mineral assemblage hypersaline fluid inclusions pseudomorphic voids and minerals after gypsum and carbonate in addition to tourmalines with isotopically light boron isotopes is interpreted as evidence for a non marine evaporite parent rock for portions of the olary block types of mineral occurrences in the olary block form a continuum between chemical sediments formed by the exhalations of hydrothermal fluids to intrasediment deposits inferred to have been formed due to the chemical changes imposed on these and or diagenetic fluids during their passage through the sedimentary pile disseminated stratabound pyrite including cobaltian types and chalcopyrite extend along strike for many kilometres and are interpreted to have formed by a diagenetic mechanism the presence of massive sulphide bearing strata iron formations barite tourmalinite and manganiferous rocks are typical of chemical sediments derived from hot spring sources the olary block meta evaporites have similar whole rock compositions to tertiary analcime rich rocks of the green river formation wyoming these new data imply that portions of the adjacent broken hill block may also comprise meta evaporites for example the quartz albite rich strata of the thackaringa group and the calcsilicates of the lower broken hill group and that the disseminated cobaltian pyrite mineralisation in the thackaringa group may not be of exhalative origin

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

textural and geochemical analysis of chalcopyrite galena and sphalerite across the mount isa cu to pb zn transition implications for a zoned cu pb zn system abstract the genesis of the mount isa cu pb zn system northern australia is highly debated three metallogenic models have previously been proposed to explain the close spatial relationship between a world class cu and pb zn deposit 1 ca 1650 ma syngenetic pb zn mineralisation that has been re mobilised and overprinted by ca 1520 ma epigenetic cu mineralisation 2 ca 1650 ma syn sedimentary cu pb zn mineralisation 3 ca 1520 ma epigenetic cu pb zn mineralisation to assess the viability of these models detailed petrography and core logging was completed on numerous samples across eight sections of drill core that intersect both cu and pb zn mineralisation this was accompanied by the analysis of trace elements in chalcopyrite galena and sphalerite from various samples across the lateral transition from cu to pb zn rich mineralisation across the cu to pb zn transition there is a primary change in host lithology from cu rich silica dolomite breccia to highly stratiform pb zn rich carbonaceous carbonate rich and fine grained pyrite rich shale petrography suggests that sphalerite galena and chalcopyrite co crystallised consistently enveloping and or replacing pre mineralisation silica dolomite siderite calcite arsenopyrite fine and coarse grained pyrite from cu to pb zn rich mineralisation sphalerite and galena transition from micro inclusions primarily located within coarse grained chalcopyrite to dominant fine to coarse grained components that infill around deformed carbonaceous shale and selectively replace carbonate rich and fine grained pyrite rich shale chalcopyrite transitions from a coarse grained component that replaces silica dolomite alteration to an uncommon medium to fine grained component residing within stratabound pb zn mineralisation trace element trends demonstrate that as pb zn mineralisation is approached the concentrations of bi in chalcopyrite cd se te bi in galena and bi and co in sphalerite decrease or are relatively depleted conversely the concentrations of pb in chalcopyrite sb in galena and pb sb and ag in sphalerite increase or are relatively enriched these trends are consistent with a temperature gradient between cu and pb zn mineralisation during ore emplacement the sphalerite ggimfis geothermometer yields a median homogenisation temperature of 343 44 c consistent with previous temperature estimates of cu mineralisation silica dolomite formation and chlorite alteration an epigenetic and coeval cu pb zn model is favoured where a slight temperature gradient

community preparedness for lava flows from mauna loa and hualālai volcanoes kona hawai i lava flows from mauna loa and hual lai volcanoes are a major volcanic hazard that could impact the western portion of the island of hawai i e g kona the most recent eruptions of these two volcanoes to affect kona occurred in a d 1950 and ca 1800 respectively in contrast in eastern hawai i eruptions of neighboring k lauea volcano have occurred frequently since 1955 and therefore have been the focus for hazard mitigation official preparedness and response measures are therefore modeled on typical eruptions of k lauea

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

comparative geothermometry of recent hawaiian eruptions in this paper we compare lava temperatures measured using cr a1 thermocouples or infrared spectrometry with estimated quenching temperatures based on the glass geothermometry calibration of helz and thornber 1987 comparative data are available for the april 1982 and september 1982 summit eruptions the pu u o o east rift eruption 1983 1986 all three eruptions at kilauea and the 1984 mauna loa eruption the results show that quenching temperatures based on the mgo contents of kilauean glasses tmgo lie within 10oc of field measurements using the infrared spectrometer for 85 of the samples where a cr a1 thermocouple was used 90 of the field measurements lie within 1 o to 11oc of tmg o for samples with tfiel d 1130oc samples where tfiel d 1130oc show larger divergence the uncertainty in tmg o by itself is 10oc so the level of agreement between field measurements and tmg o is very good for kilauean lavas systematic comparison of field measurements of temperature with glass geothermometry for the 1984 mauna loa eruption suggests that although the field and glass temperatures lie within 10oc of each other the kilauean tmg o calibration is nevertheless not appropriate for mauna loa glasses and that actual quenching temperatures for mauna loa samples will lie 10o 20oc higher than would be predicted from the kilauea calibration curve consideration of possible effects of variable volatile content suggest that in most cases these are small samples erupted early in an eruption may reflect preeruptive water contents different enough to affect tmg o significantly but later spatter samples and all flow samples appear to have equilibrated at low enough water contents for the calibration to be applicable we conclude that the mgo based geothermometer can be applied to glassy kilauean samples to give temperatures that generally will lie within 10oc of a field measurement plots of glass mgo content versus time if a suitable sample base is available should give a thorough quantitative record of the thermal history of any kilauean eruption

sulfur isotope constraints on the conditions of pyrite formation in the paleoproterozoic urquhart shale formation and george fisher zn pb ag deposit northern australia

observations on basaltic lava streams in tubes from kilauea volcano island of hawai i from 1986 to 1997 the pu u o o kupaianaha eruption of kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10 12 km from vents on the volcano s east rift zone to the ocean within a kilometer of the vent tubes were as much as 20 m high and 10 25 m wide on steep slopes 4 10 a little farther away from the vent some tubes formed by roofing over of lava channels lava streams were typically 1 2 m deep flowing within a tube that here was typically 5 m high and 3 m wide on the coastal plain 1 tubes within inflated sheet flows were completely filled typically 1 2 m high and several tens of meters wide tubes develop as a flow s crust grows on the top bottom and sides of the tubes restricting the size of the fluid core the tubes start out with nearly elliptical cross sectional shapes many times wider than high broad flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting sometimes the tubes began downcutting progressive downcutting was frequently observed through skylights a rate of 10 cm d was measured at one skylight for nearly 2 months

a geochemical process model for the mount isa copper orebodies in this paper we present new data and review existing data on the distribution lithochemistry and paragenesis of copper ore at mount isa and provide the first description of a body of anhydrite dolomite barite and hematite recently intersected at the northern end of the copper system it has been previously proposed that the extraordinary spatial coincidence of giant copper and lead zinc deposits at mount isa is due to the emplacement of copper into host rocks made chemically favorable for copper mineralization by enrichment in dolomite and or pyrite and mechanically favorable by the presence of preexisting layers of ductile lead and zinc sulfide ore several recent studies however suggest that copper and much if not all of the lead and zinc were deposited contemporaneously we provide evidence that high grade 2 5 copper is associated with fractured and silicified rocks early breccia cementing quartz is commonly euhedral and contains numerous growth zones defined by disordered carbon and brine inclusions containing ch4 this quartz is inferred to have been deposited from a cooling brine basement brine that equilibrated with rocks beneath the level of the deposit consistent with earlier studies we have noted that there is often late dolomite dolomite ii infilling of vuggy porosity defined by this euhedral quartz chalcopyrite however postdates both phases and there is textural evidence of both dolomite and quartz dissolution during chalcopyrite formation the nature of the copper bearing fluid basinal brine was deduced from the intimate association of chalcopyrite and anhydrite and from previous fluid inclusion studies this brine was oxidized and sulfur rich but undersaturated in quartz consistent with this fluid being introduced from above as proposed in several previous studies new reaction path modeling suggests that reduction of the oxidized brine by the carbonaceous and urquhart shale was the most likely depositional process many other rock types in the region also had the capacity to reduce oxidized ore forming brines thus ore can be anticipated in these other units provided that sufficient porosity and permeability existed during ore formation the modeling further suggests that the presence of dolomite is not a prerequisite to economic copper grades although carbonate dissolution possibly contributed with fracturing to enhanced porosity and permeability furthermore sulfide rich rocks were no more effective at precipitating copper than sulfide absent rocks consistent with several lines of evidence demonstrating that pyrite or other sulfide minerals were not consumed during ore formation mixing of the basinal and basement brines could also have caused precipitation of copper but the predicted gangue assemblages differ from those observed in nature various radiometric ages are consistent with formation of the mount isa copper deposits after initiation of the unconformable south nicholson basin although we recognize that more precise and accurate dating of the ore and fluid flow events are required basal red bed sediments of the south nicholson basin would have provided suitable aquifers for the oxidized copper rich basinal brines we speculate that the driving force for brine flow was the development of topography to the east of mount isa

volcanic features of the north rockall trough application of visualisation techniques on 3d seismic reflection data understanding the volcanic processes operating during continental break up is hampered by the subsequent burial of the majority of the volcanic pile beneath thick sedimentary sequences currently located in bathymetrically deep offshore regions although portions of these volcanic systems are currently exposed on land a full understanding of the volcanic structure the eruptive styles and their evolution is not possible as these localities have been partially eroded furthermore as the onshore exposure represents a volumetrically minor part of the entire system the documented eruptive styles may not be representative the increasing availability of 3d seismic reflection data has the potential to significantly enhance our understanding of break up related volcanism as it allows direct access to detailed information from the buried volcanic succession however conventional seismic interpretation methodologies cannot determine lava flow morphologies and as a result eruptive styles and their evolution are still largely based on extrapolation from the accessible onshore outcrop data new 3d seismic volume visualisation techniques allow the buried basalt morphologies to be examined for the first time in a manner similar to outcrop aerial photographic or satellite based observations applying this new approach for 3d seismic data to the north rockall trough u k atlantic margin demonstrates that a range of volcanic features indicative of eruptive style can be determined the data reveal a complex terrain containing lava flows originating from discrete volcanic centres contemporaneous normal faults linear fissures a few kilometres long radial fissures and inflation ridges lava flow morphologies that are indicative of tube fed inflated sheetflows intracanyon flows and elongate subaerial flows that enter water downslope to produce a large hyaloclastite delta are observed

the influence of slope breaks on lava flow surface disruption changes in the underlying slope of a lava flow impart a significant fraction of rotational energy beyond the slope break the eddies circulation and vortices caused by this rotational energy can disrupt the flow surface having a significant impact on heat loss and thus the distance the flow can travel a basic mechanics model is used to compute the rotational energy caused by a slope change the gain in rotational energy is deposited into an eddy of radius r whose energy is dissipated as it travels downstream a model of eddy friction with the ambient lava is used to compute the time rate of energy dissipation the key parameter of the dissipation rate is shown to be r2 where is the lava density and is the viscosity which can vary by orders of magnitude for different flows the potential spatial disruption of the lava flow surface is investigated by introducing steady state models for the main flow beyond the steepening slope break one model applies to slow moving flows with both gravity and pressure as the driving forces the other model applies to fast moving low viscosity turbulent flows these models provide the flow velocity that establishes the downstream transport distance of disrupting eddies before they dissipate the potential influence of slope breaks is discussed in connection with field studies of lava flows from the 1801 hualalai and 1823 keaiwa kilauea hawaii and 2004 etna eruptions

the perception of volcanic risk in kona communities from mauna loa and hualālai volcanoes hawai i abstract volcanic hazards in kona i e the western side of the island of hawai i stem primarily from mauna loa and hual lai volcanoes the former has erupted 39 times since 1832 lava flows were emplaced in kona during seven of these eruptions and last impacted kona in 1950 hual lai last erupted in ca 1800 society s proximity to potential eruptive sources and the potential for relatively fast moving lava flows coupled with relatively long time intervals since the last eruptions in kona are the underlying stimuli for this study of risk perception target populations were high school students and adults n 462 using these data we discuss threat knowledge as an influence on risk perception and perception as a driving mechanism for preparedness threat knowledge and perception of risk were found to be low to moderate on average fewer than two thirds of the residents were aware of the most recent eruptions that impacted kona and a minority felt that mauna loa and hual lai could ever erupt again furthermore only about one third were aware that lava flows could reach the coast in kona in less than 3 h lava flows and ash fall were perceived to be among the least likely hazards to affect the respondent s community within the next 10 years whereas vog volcanic smog was ranked the most likely less than 18 identified volcanic hazards as amongst the most likely hazards to affect them at home school or work not surprisingly individual preparedness measures were found on average to be limited to simple tasks of value in frequently occurring domestic emergencies whereas measures specific to infrequent hazard events such as volcanic eruptions were seldom adopted furthermore our data show that respondents exhibit an unrealistic optimism bias and infer that responsibility for community preparedness for future eruptions primarily rests with officials we infer that these respondents may be less likely to attend to hazard information react to warnings as directed and undertake preparedness measures than other populations who perceive responsibility to lie with themselves there are significant differences in hazard awareness and risk perception between students and adults between subpopulations representing local areas and between varying ethnicities we conclude that long time intervals since damaging lava flows have occurred in kona have contributed to lower levels of awareness and risk perceptions of the threat from lava flows and that the on going eruption at k lauea has facilitated greater awareness and perception of risk of vog but not of other volcanic hazards low levels of preparedness may be explained by low perceptions of threat and risk and perhaps by the lack of a clear motivation or incentive to seek new modes of adjustment

hawaiian xenolith populations magma supply rates and development of magma chambers hawaiian volcanoes pass through a sequence of four eruptive stages characterized by distinct lava types magma supply rates and xenolith populations magma supply rates are low in the earliest and two latest alkalic stages and high in the tholeiitic second stage magma storage reservoirs develop at shallow and intermediate depths as the magma supply rate increases during the earliest stage magma in these reservoirs solidifies as the supply rate declines during the alkalic third stage these magma storage reservoirs function as hydraulic filters and remove dense xenoliths that the ascending magma has entrained during the earliest and latest stages no magma storage zone exists and mantle xenoliths of lherzolite are carried to the surface in primitive alkalic lava during the tholeiitic second stage magma storage reservoirs develop and persist both at the base of the ocean crust and 3 7 km below the caldera only xenoliths of shallow origin are carried to the surface by differentiated lava during the alkalic third stage magma in the shallow subcaldera reservoir solidifies and crustal xenoliths including oceanic crustal rocks are carried to the surface in lava that fractionates in an intermediate depth reservoir worldwide xenolith populations in tholeiitic and alkalic lava may reflect the presence or absence of subvolcanic magma storage reservoirs

geochemistry of 1 8 1 67 ga mudstones and siltstones from the mount isa inlier queensland australia provenance and tectonic implications abstract sedimentary and volcanic rocks overlying basement in the mount isa inlier australia are subdivided into three cover sequences the upper two sequences range in age from 1800 to 1670 ma and each consist of rift and overlying sag phases of sedimentation fine grained siliciclastic sedimentary rocks in the upper two sequences define two distinct geochemical groups samples from groups i and ii are mainly from the lower and upper rift and upper thermal phases respectively one sample from the lower rift phase has affinities with group ii whereas samples from the lower thermal phase belong to both groups i and ii eu eu values are 0 70 to 0 85 for group iand 0 55 to 0 70 for group ii group i samples are characterized by lower la sc and th sc ratios and higher cr th ratios than group ii cr niand co concentrations are greater in group i than group ii groups i and ii also are distinguished on plots of eu eu vs lan smn and eu eu vs gdn ybn two samples from group i have elevated lree hree and lan ybn ratios that are attributed to intense weathering as revealed by their high chemical index of weathering values the geochemical data reflect a combination of local and more distant regional provenances and can be related to the tectonic evolution of the mount isa inlier group i samples are attributed to dilution of a mature post archean source by addition of recycled mafic volcanics group ii samples are typical post archean sediments derived from differentiated upper continental crust with no dilution by local sources the lower rift phase displays great geochemical variability samples from both groups that is typical of active tectonic settings such as rifts the great variability of samples from the lower sag phase both groups is surprising but probably reflects the diverse rock types beneath this basin stable tectonic conditions during this phase of sedimentation are indicated instead by major element geochemistry that records severe weathering similarity of the upper rift phase sample with some samples from the lower sag phase reflects recycling of the latter samples from the upper sag phase are remarkably uniform in composition group ii and reflect the stable tectonic conditions under which this basin developed

volcanic processes as alternative mechanisms of landform development at a candidate crater lake site near tyrrhena patera mars 1 palos crater a prominent candidate crater lake site in the hesperia region of mars is located at the mouth of a sinuous inlet channel that extends from the northern flanks of tyrrhena patera previous studies of this site have concluded that channels and basin infill units likely formed through aqueous processes that partly involved karst like removal of materials in the subsurface by the flow of groundwater as with many locales on mars the aqueous processes hypothesized to have been involved in the formation and evolution of terrain features are compelling however the characteristics of this site suggest that an alternative set of mechanisms for landform development should be considered alongside aqueous hypotheses the main attributes of channels and infill of the central crater include 1 an association with a very large volcanic rise to the south 2 the existence of roofed segments of the main inlet channel and 3 infill of the central crater and outlet channel by materials that have characteristics consistent with those expected of volcanic plains these general attributes are consistent with formation through or in association with processes that involved the flow of lava although a volcanic model may account for the presence and basic nature of landforms previously considered supportive of a paleolake interpretation of the site an overprint of dendritic valley networks on parts of the inlet system suggests that aqueous processes may have also acted in the evolution of the site a complex interrelation between past igneous and aqueous processes at this site is possible

leucocratic and gabbroic xenoliths from hualalai volcano hawai i a diverse range of crustal xenoliths is hosted in young alkali basalt lavas and scoria deposits erupted 3 5 ka at the summit of hual alai leucocratic xenoliths including monzodiorites diorites and syenogabbros are distinctive among hawaiian plutonic rocks in having alkali feldspar apatite zircon and biotite and evolved mineral compositions e g albitic feldspar clinopyroxene mgnumber 67 78 fine grained diorites and monzodiorites are plutonic equivalents of mugearite lavas which are unknown at hual alai these xenoliths appear to represent melt compositions falling along a liquid line of descent leading to trachyte a magma type which erupted from hual alai as a prodigious lava flow and scoria cone at 114 ka inferred fractionating assemblages melts modeling pyroxene geobarometry and whole rock norms all point to formation of the parent rocks of the leucocratic xenoliths at 3 7 kbar pressure this depth constraint on xenolith formation coupled with a demonstrated affinity to hypersthenenormative basalt and petrologic links between the xenoliths and the trachyte suggests that the shift from shield to post shield magmatism at hual alai was accompanied by significant deepening of the active magma reservoir and a gradual transition from tholeiitic to alkalic magmas subsequent differentiation of transitional basalts by fractional crystallization was apparently both extreme culminating in 5 5 km of trachyte and rapid at 2 75 10 m magma crystallized year

noble gas and halogen constraints on mineralizing fluids of metamorphic versus surficial origin mt isa australia abstract the origin of hydrothermal fluids responsible for silica dolomite alteration associated with cu ore in the giant mt isa deposit of queensland north east australia has been investigated main stage quartz and dolomite veins and late to post ore quartz from the buck quartz fault in the orebody footwall plus the regional mt isa and railway faults contain two phase liquid vapour fluid inclusions with variable salinity fluid inclusion molar br cl values are mostly in the range 1 5 12 10 3 and molar i cl values are in the range 9 186 10 6 greater than seawater br cl and i cl values can characterise either sedimentary formation waters with a bittern brine origin by the sub aerial evaporation of surface water beyond the point of halite saturation or some metamorphic dehydration fluids with a deep crustal source we propose that these alternative origins can be distinguished in our samples based on the relationship between 40 ar 36 ar and 36 ar concentration metamorphic fluids formed by dehydration of crystalline rock are predicted to have low 36 ar concentrations with the salinity 40 ar 36 ar and 40 ar e cl values determined by the whole rock concentration of cl 36 ar oh k and age the main stage quartz and buck quartz fault samples host fluid inclusions with 36 ar 40 ar 36 ar in the range 10 000 28 000 and high 40 ar e cl values of 3 8 10 4 these values are consistent with metamorphic fluids sourced by devolatilisation of either the underlying eastern creek volcanics or the barramundi basement in contrast surface derived fluids acquire elevated 40 ar 36 ar values 296 through fluid rock interaction which leads to a simultaneous increase in 36 ar concentration the main stage ca rich dolomite fluid inclusions have high salinities close to the point of halite saturation 26 wt 1 7 5 5 ppb 36 ar 40 ar 36 ar in the range 1600 8400 and 40 ar e cl of 0 2 1 10 4 these values are most similar to those expected in an evolved bittern brine however the 36 ar concentration and 40 ar 36 ar value exhibit a weakly negative correlation which is the opposite to that expected in surface derived fluids only fluid inclusions in samples from the railway fault and some fluid inclusions in samples from the buck quartz fault have 36 ar concentrations of greater than air saturated water asw 1 3 2 7 ppb 36 ar up to 27 ppb and 40 ar 36 ar values of 1000 2500 that are expected for fluids with an exclusively sedimentary formation water origin fluid inclusions in the mt isa fault samples have the highest 36 ar concentrations of up to 100 ppb some of the lowest 40 ar 36 ar values and the highest br cl value of up to 30 10 3 these features distinguish it from all other sample groups in the mine area silica dolomite alteration and cu mineralization are interpreted to have resulted from mixing of the deeply derived metamorphic fluid best preserved in quartz fluid inclusions and a surface derived bittern brine partially preserved within the main stage dolomite fluid inclusions inflow of a second surficial fluid along regional faults and into the mine through the late to post d 3 buck quartz fault may have terminated mineralization the involvement of metamorphic fluids is compatible with the syn d 3 1530 ma timing of mineralization during the final stages of the isan orogeny