monitoring volcano slope instability with synthetic aperture radar a review and new data from pacaya guatemala and stromboli italy volcanoes abstract volcano slope instability manifests in many forms ranging from steady state to punctuated movement or shallow erosion to deep seated spreading the interplay of gravity magmatic or hydrothermal fluids and often active tectonics on a volcanic edifice results in complex spatial and temporal variations in deformation kinematics while this makes the recognition assessment and monitoring of volcano slope instability challenging advancements in synthetic aperture radar sar technology have significantly accelerated our knowledge of instability phenomena and our ability to assess their hazards this review discusses the applications and challenges of sar imagery to various slope instabilities at volcanoes around the world sar amplitude images are powerful tools for mapping areas of geomorphological changes these snapshots can be combined using interferometric sar insar to create multi temporal deformation maps that provide unique information on the evolution of slope failures space borne insar has become an economic way to detect changes at volcanoes at very high resolution ground based insar gbinsar can produce frequent sar images on the order of seconds to minutes propelling insar from monitoring to surveillance and early warning applications however interpreting insar derived ground deformation signals related to volcano slope instability is still challenging deformation from magma rise or variations in hydrothermal systems may be inseparable from persistent deep seated flank motion similarly shallow or localized ground motion may occur in overlap with thermal contraction or subsidence of newly emplaced lava or tephra deposits if triggered to failure landslides can vary over several magnitudes from small volume rock falls that pose only a localized hazard to large volume debris avalanches capable of travelling tens of kilometers away from the source these collapses can have cascading hazards if accompanied by directed blasts or tsunamis emphasizing the need for continued advancement of our understanding of these events and their consequences to highlight the utility of sar for measuring and monitoring mass movement two case studies of stromboli italy and pacaya guatemala volcanoes are discussed in detail where recent instability events persistent volcanic activity and ground truth constraints have resulted in excellent case histories in applying sar imagery to understand these potentially hazardous slope instabilities

gravity changes and deformation due to a magmatic intrusion in a two layered crustal model we develop and extend theoretical and computational methods for the calculation of the deformation gravity and potential change due to a point source of magma injection into a multilayered elastic gravitational earth model in our calculations which are based upon the method outlined by rundle two distinct layers overlying a half space may be incorporated the source can be located in either of the layers or the half space the method is quite general and can be readily adapted to calculations in which stresses in either the layers or the half space relax by viscoelastic flow the results obtained indicate that the use of homogeneous half space to represent the earth may in some cases be too simple a model and that variations in elastic moduli have a more significant effect than variation in reference density on both the surface displacements and gravity changes as an example we calculate the displacement and gravity changes due to a subsurface mass injection in a crust mantle model appropriate to the volcanic island of lanzarote which is presently the subject of numerous geophysical experiments both historical and recent data indicate that lanzarote may be subject to some risk of volcanic eruption in the future thus our calculations may be useful in interpreting observations of preemption phenomena the results are discussed in terms of prediction versus measurement capabilities

scouring of gold from the lower crust quartz carbonate lodes have produced a major part of the world9s gold the source for the lodes which were emplaced along shear zones in the upper crust has been enigmatic the bamble belt of south norway is depleted in gold by more than an order of magnitude relative to its crustal abundance other elements present in gold deposits have also been lost gold dissolved and was removed in oxidized sulfur rich fluids rising through this broad ductile shear zone during high grade metamorphism deformation synchronous with metamorphism created the permeability that permitted a pervasive flow of fluids

halogen systematics in the mallik 5l 38 gas hydrate production research well northwest territories canada implications for the origin of gas hydrates under terrestrial permafrost conditions abstract the authors report here halogen concentrations in pore waters and sediments collected from the mallik 5l 38 gas hydrate production research well a permafrost location in the mackenzie delta northwest territories canada iodine and br are commonly enriched in waters associated with ch4 reflecting the close association between these halogens and source organic materials pore waters collected from the mallik well show i enrichment by one order of magnitude above that of seawater particularly in sandy layers below the gas hydrate stability zone ghsz although cl and br concentrations increase with depth similar to the i profile they remain below seawater values the increase in i concentrations observed below the ghsz suggests that i rich fluids responsible for the accumulation of ch4 in gas hydrates are preferentially transported through the sandy permeable layers below the ghsz the br and i concentrations and i br ratios in mallik are considerably lower than those in marine gas hydrate locations demonstrating a terrestrial nature for the organic materials responsible for the ch4 at the mallik site halogen systematics in mallik suggest that they are the result of mixing between seawater freshwater and an i rich source fluid the comparison between i br ratios in pore waters and sediments speaks against the origin of the source fluids within the host formations of gas hydrates a finding compatible with the results from a limited set of 129i i ratios determined in pore waters which gives a minimum age of 29 ma for the source material i e at the lower end of the age range of the host formations the likely scenario for the gas hydrate formation in mallik is the derivation of ch4 together with i from the terrestrial source materials in formations other than the host layers through sandy permeable layers into the present gas hydrate zones

lead and zinc in formation waters alberta basin canada their relation to the pine point ore fluid abstract the source of the ore fluid for the pine point zn pb deposit has been controversial for decades both formation waters from deep in the basin and geothermal fluids from the precambrian basement have been considered as sources of the ore in this carbonate hosted deposit a database of 694 analyses of pb and zn in formation waters from the alberta basin bears on this controversy these waters have a mean content of 4 66 mg l 1 pb and 6 88 mg l 1 zn for each of these metals the maximum content is 360 mg l 1 and the median content is 0 9 mg l 1 in 71 of the samples pb zn with a mean ratio of 2 3 1 this is in contrast to the pb zn ratio of formation waters in other sedimentary basins and geothermal waters but is consistent with that in brines from the canadian shield geochemical modelling using solmineq 88 shows that pb and zn occur mainly as the mecl 4 2 complex it is not possible to produce a sulphide precipitate with zn pb such as the ore at pine point from a formation water with pb zn even when the formation water carries the metals in the absence of h2s and the metals are precipitated by h2s rich brines therefore the present formation waters are a poor candidate for the source of the metals at pine point it is more likely that geothermal fluids rising along the great slave lake shear zone were the source of the metals additional evidence for this alternate source includes 1 the very homogeneous non radiogenic character of the pb isotopes in galena 2 the absence of a thermal anomaly along the great slave lake shear zone 3 a famennian time of deposition based on rb sr dating of sphalerite when overburden was thin and reservoir temperature low and 4 the distribution of sphalerite and galena in the subsurface of the alberta basin in relation to major crustal discontinuities and normal faults cutting the crystalline basement exploration for other zn pb deposits should therefore focus on the location of suitable shear zones and faults up which geothermal fluids might have migrated rather than the flow and composition of formation waters

gravity driven deformation of tenerife measured by insar time series analysis 1 we study the state of deformation of tenerife canary islands using differential synthetic aperture radar interferometry dinsar we apply the small baseline subset sbas dinsar algorithm to radar images acquired from 1992 to 2005 by the ers sensors to determine the deformation rate distribution and the time series for the coherent pixels identified in the island our analysis reveals that the summit area of the volcanic edifice is characterized by a rather continuous subsidence extending well beyond las canadas caldera rim and corresponding to the dense core of the island these results coupled with gps ones structural and geological information and deformation modeling suggest an interpretation based on the gravitational sinking of the dense core of the island into a weak lithosphere and that the volcanic edifice is in a state of compression we also detect more localized deformation patterns correlated with water table changes and variations in the deformation time series associated with the seismic crisis in 2004

halogen and ar ar age determinations of inclusions within quartz veins from porphyry copper deposits using complementary noble gas extraction techniques abstract extension of ar ar methodology has been used to determine mineralisation ages from mica inclusions and to simultaneously evaluate the noble gas and halogen composition of inclusion fluids within irradiated quartz vein samples from five porphyry copper deposits samples have been collected from the potassic and propylitic zones of bingham canyon utah and four arizonan deposits silverbell globe miami pinto valley and ray data obtained using three noble gas extraction techniques laser ablation in vacuo crushing and stepped heating are compared with each other laser ablation provides a means for the analysis of individual fluid inclusions but is limited by blank levels and detection limits stepped heating and in vacuo crushing are bulk extraction techniques that preferentially release gases from solid and fluid inclusion phases respectively and can be used in combination to obtain accurate and meaningful ages of mineralisation ages obtained for porphyry copper deposits are as follows bingham canyon 37 1 0 5 ray 65 3 1 5 globe miami 61 7 3 4 pinto valley 63 2 8 0 and silverbell 55 8 1 8 the age of mineralisation at ray is of particular interest as it enables a reported discrepancy in k ar ages to be understood halogen data for the bingham canyon samples gives insight into the partitioning of the heavy halogens br and i between solid and liquid phases

a seismic study of lithospheric flexure in the vicinity of tenerife canary islands seismic data have been used to determine the crustal and upper mantle structure of tenerife canary islands a volcanic island of tertiary age located on 140 ma oceanic crust reflection data show that oceanic basement dips gently towards the island forming a flexural moat which is infilled by 2 3 km of well stratified material the moat is characterised by a major angular unconformity which we attribute to volcanic loading of pre existing oceanic crust and overlying sediments and the subsequent infilling of the flexure by material that was derived at least in part from the islands refraction data show that the flexed oceanic crust has a mean thickness of 6 41 0 42 km and upper and lower crustal velocities of 4 8 5 4 km s 1 and 6 7 7 3 km s 1 respectively the flexure which has been verified by gravity modelling can be explained by a model in which tenerife and adjacent islands have loaded a lithosphere with a long term 106 yr elastic thickness of approximately 20 km seismic and gravity data suggest that up to 1 5 105 km3 of magmatic material has been added to the surface of the flexed oceanic crust which assuming an age of 6 16 ma for the shield building stage on tenerife implies a magma generation rate of about 0 006 to 0 02 km3 a 1 this rate is similar to estimates from other african oceanic islands e g reunion and cape verdes but is significantly less than that which has been calculated at hawaii there is no evidence in either the seismic or gravity data that any significant amount of magmatic material has underplated the flexed oceanic crust the crustal and upper mantle structure at tenerife therefore differs from other oceanic islands such as hawaii and marquesas where 4 km of underplated material have been reported

monitoring the daytime variations of equatorial ionospheric anomaly using ionex data and champ gps data a method which can invert the ionospheric electron content above the champ satellite is presented the daytime behavior of the equatorial ionospheric anomaly eia is monitored using the champ global positioning system data and the ionosphere map exchange format data supplied by the center for orbit determination in europe during the period at quiet geomagnetic conditions between november 7 and december 12 2003 results show that the plasma congregates and rises above the geomagnetic equator due to the daytime upward vertical drift during the early variations of eia after being lifted to higher altitudes the topside ionospheric equatorial plasma above the champ orbit over 400 km above the ground controlled mainly by the electromagnetic field starts to diffuse downward to higher latitudes along magnetic field lines and the double humped structure begins to appear in the topside ionosphere above the champ orbit however a single crest is still observed for the entire ionosphere above the ground and this single peak moves slightly to the winter hemisphere as a result of the transequatorial neutral wind with the continuous diffusion of the plasma the two crests also occur for the entire ionosphere at both sides of the geomagnetic equator

vertical and lateral collapses on tenerife canary islands and other volcanic ocean islands recent studies demonstrate that tenerife has undergone large lateral collapses this has led to the suggestion that the las canadas caldera one of the best exposed calderas in the world is the result of lateral collapse we have tested this idea using the available structural stratigraphic volcanological and geochronological data we conclude that the las canadas caldera is the result of a complex sequence of vertical collapse events associated with a long history of phonolitic explosive activity in the central part of tenerife our results indicate however that vertical collapses may have played a major role in triggering lateral collapses we propose that the association of vertical and lateral collapse events such as inferred for tenerife can also explain similar sequences of events interpreted to have affected other large volcanic ocean islands

multidimensional time series analysis of ground deformation from multiple insar data sets applied to virunga volcanic province summary a novel multidimensional small baseline subset msbas methodology is presented for integration of multiple interferometric synthetic aperture radar insar data sets for computation of 2 or 3 d time series of deformation the proposed approach allows the combination of all possible air borne and space borne sar data acquired with different acquisition parameters temporal and spatial sampling and resolution wave band and polarization the produced time series have improved temporal resolution and can be enhanced by applying either regularization or temporal filtering to remove high frequency noise we apply this methodology to map 2003 2010 ground deformation of the virunga volcanic province vvp north kivu democratic republic of congo the horizontal and vertical time series of ground displacement clearly identify lava compaction areas long term deformation of mt nyamuragira and 2004 2006 and 2010 pre and coeruptive deformation providing that enough sar data is available the method opens new opportunities for detecting ground motion in the vvp and elsewhere

principal component analysis of msbas dinsar time series from campi flegrei italy abstract because of its proximity to the city of naples and with a population of nearly 1 million people within its caldera campi flegrei is one of the highest risk volcanic areas in the world since the last major eruption in 1538 the caldera has undergone frequent episodes of ground subsidence and uplift accompanied by seismic activity that has been interpreted as the result of a stationary deeper source below the caldera that feeds shallower eruptions however the location and depth of the deeper source is not well characterized and its relationship to current activity is poorly understood recently a significant increase in the uplift rate has occurred resulting in almost 13 cm of uplift by 2013 de martino et al 2014 samsonov et al 2014b di vito et al 2016 here we apply a principal component decomposition to high resolution time series from the region produced by the advanced multidimensional sbas dinsar technique in order to better delineate both the deeper source and the recent shallow activity we analyzed both a period of substantial subsidence 1993 1999 and a second of significant uplift 2007 2013 and inverted the associated vertical surface displacement for the most likely source models results suggest that the underlying dynamics of the caldera changed in the late 1990s from one in which the primary signal arises from a shallow deflating source above a deeper expanding source to one dominated by a shallow inflating source in general the shallow source lies between 2700 and 3400 m below the caldera while the deeper source lies at 7600 m or more in depth the combination of principal component analysis with high resolution msbas time series data allows for these new insights and confirms the applicability of both to areas at risk from dynamic natural hazards

the origin and evolution of mineralizing fluids in a sediment hosted orogenic gold deposit ballarat east southeastern australia the hydrothermal fluids responsible for gold mineralization at the ballarat east gold deposit the second largest orogenic gold deposit in the western lachlan orogen are thought to have links to a variety of processes including metamorphism sedimentation and or magmatism in the current study noble gases and halogens have been used as fluid tracers to reevaluate the origin and evolution of the gold related fluids at the ballarat east deposit gold bearing quartz and carbonate veins from the ballarat east contain low salinity 4 wt nacl equiv aqueous h2o and mixed h2o co2 fluid inclusions these fluid inclusions have variable molar br cl values of between 1 2 10 3 and 2 9 10 3 and i cl values between 150 10 6 and 500 10 6 and br is strongly correlated with i defining a mixing line with a br i ratio of 5 6 the fluid inclusions have 40ar 36ar ratios ranging from 322 close to the atmospheric 40ar 36ar ratio of 296 up to a maximum of 4503 40ar is strongly correlated with cl and defines a mixing line with a 40are cl ratio of 4 6 10 4 40are denotes excess 40ar the fluid inclusions contain 5 1 to 32 ppm 40are by mass and exhibit minimum 36ar concentrations ranging from 3 1 to 11 ppb which exceed air saturated water asw levels by several parts per billion asw 1 3 2 7 ppb fluid inclusion 84kr 36ar and 130xe 36ar values are uniformly enriched in kr and xe relative to air but exhibit limited variation these data provide strong evidence for the involvement of two noble gas and halogen reservoirs this data is compatible with a deeply sourced fluid possibly originating by devolatilization of altered volcanic rocks e g basalts that acquired additional noble gases and organic br plus i by interaction with sedimentary rocks including organic rich shales that are found beneath and surrounding the deposit the data are also consistent with mixing deeply sourced metamorphic fluids with sedimentary formation waters however both interpretations favor the involvement of metamorphic fluids and sedimentary components and highlight the significance of fluid rock interaction as controls on fluid compositions in victorian deposits the data are compatible with genetic models for orogenic gold in which gold mineralization was initiated by metamorphic devolatilization in the lower crust and was linked to lachlan orogenesis at ca 440 ma

long term versus short term deformation processes at tenerife canary islands 1 several geophysical investigations have identified that the tenerife volcanic complex is affected by crustal deformation processes occurring at timescales of millions of years recently space based geodetic observations have also detected a short term surface deformation characterized by a broad subsidence pattern with maximum ground velocities of about 4 mm yr 1 for the purpose of investigating the relationship between these long term and short term deformation processes we performed an advanced fluid dynamic analysis fda we first carried out a standard dimensionless fda to discriminate the deformation style of tenerife and found that at million year timescales basement flexure mainly controls its long term structural evolution secondly to highlight the driving forces of the short term deformation process we simulated a numerical fda based on finite element models that include topography as well as vertical and lateral material heterogeneities our results show that the recent surface deformation is mainly caused by a progressive sagging of the denser less viscous core of the island onto the weaker but more viscous lithosphere moreover over periods comparable to the hypothesized age of loading of the oceanic crust beneath tenerife this tendency would result in a total flexure of about 3 4 km which is in agreement with independent estimations based on geophysical analyses our study shows that a unitary physical model may explain both the deformation recorded in deep geological structures and the current active ground deformation processes occurring at the tenerife volcano

internal structure of tenerife canary islands based on gravity aeromagnetic and volcanological data abstract gravity and magnetic methods have been applied to the tenerife island to provide new information about its internal structure for this study 365 gravity stations covering the central part of the island have been selected the anomalous density maps at different depths were obtained by means of an inversion global adjustment on fixed density contrast to describe the three dimensional 3d geometry of the anomalous bodies on the other hand several analysis techniques such as reduction to the pole spectral analysis low pass filtering terrain correction and forward modelling were applied to process the high resolution data obtained in an aeromagnetic survey completed with marine and terrestrial data the joint analysis of gravity and magnetic anomalies has shown tectonic and volcanic features that define some fundamental aspects of the structural framework and volcanic evolution of the island a strong gravity anomaly produced by a large and deep source has been associated with an uplifted block of the basement beneath the southern part of tenerife the sources of the observed gravity highs from 8 km b s l may be associated with the growth of the submarine shield stage that was clearly controlled by regional tectonic the long wavelength magnetic anomalies reveal highly magnetic sources interpreted as gabbro ultramafic cumulates associated with the root zone of a large dyke swarm this intrusive body could be topped by the emplacement zone of magma chambers that correlate with a magnetic horizon at 5 7 0 8 km depth rooted in this highly magnetic zone two dike like structures can be associated with the magmatic feeding system of large recent basaltic volcanoes a shallow magnetic horizon 1 4 km a s l can be correlated with the bottom phonolites of the las canadas edifice in the central part of the island the coincidence of some gravity and magnetic lows is consistent with the presence of low density and low magnetic materials that infill a collapsed caldera system the structures close to the surface are characterised by low density areas connected with the recent volcanism in particular the minimum over the teide volcano hydrothermal alteration is assumed to be the cause of a short wavelength magnetic low over the teide volcano

spatial distribution of ionization in the equatorial and low latitude ionosphere of the indian sector and its effect on the pierce point altitude for gps applications during low solar activity periods 1 the equatorial and low latitude ionosphere is characterized by dynamic changes in the spatial distribution of f region electron density the in situ density data from indian sross c2 satellite was used in conjunction with the international reference ionosphere iri to demonstrate how the median models have limitations to represent the spatial gradients in the equatorial and subtropical latitudes in the indian sector the ground based ionosonde data was used to derive the bottomside electron density profiles which were matched with iri to derive the complete f region electron density profile for different times to show the variability in the centroid of ionization mass distribution due to the equatorial plasma dynamics associated with appleton ionization anomaly the study brings out that a uniform ionospheric pierce point altitude cannot be assumed for gps applications in this sector however during low sunspot activity periods the gps derived total electron content tec using 2 2 grid point data indicates that spatial gradients in tec are not too significant in meridian transects and that the assumption of homogeneous distribution is valid for the conversion of slant to vertical tec even in the equatorial latitudes during solar minimum keeping this in view a qualitative study has been carried out on the possible variability in ionospheric pierce point altitude at representative subtropical latitude in the indian sector and the results are discussed in light of diurnal and seasonal features of the equatorial ionosphere

colonsay and islay a suspect terrane within the scottish caledonides colonsay and the western part of islay southern hebridean islands of scotland consist of unfossiliferous deformed low grade metasedimentary rocks which rest with sheared unconformity upon gneissic basement the area has a long history of investigation but its stratigraphic affinities have been a persistent problem the speculative assignment of the basement rocks to the lewisian has never been substantiated the age of the cover sequence remains unclear its deformation differs from that of nearby caledonian successions small igneous bodies have yielded a tentative intrusion age of ca 600 ma which is abnormal for the region because the area is bounded by major strike slip faults it is suggested that the colonsay western islay terrane is allochthonous probably emplaced between 620 and ca 540 ma the terrane concept explains the long standing difficulties of correlation recognition of suspect terranes even of this small size within orogens such as the orthotectonic caledonides can help resolve some long standing problems

tectonothermal history of the western lachlan fold belt australia insights from white mica studies detailed b lattice parameter and illite crystallinity ic studies of k white micas in slates from the stawell and ballarat bendigo zones sz bbz in the western lachlan fold belt of victoria australia reveal a metamorphic pattern characterized by regional metamorphism associated with crustal thickening and younger contact metamorphism accompanied by deformation the ic data indicate that rocks regionally metamorphosed prior to the intrusion of the early and late devonian granitoids vary in grade from epizonal greenschist facies to diagenetic zeolite facies and that most are of epizonal to anchizonal prehnite pumpellyite facies grade in the bbz a decrease in grade from west to east occurs across fault zones ic values show little change indicating that limited vertical displacement has occurred this is in accord with the thin skinned deformation model proposed for the western lachlan fold belt the b lattice parameters x 9 022 a n 137 s n 0 009 indicate baric conditions intermediate between those of new hampshire p al 2 sio 5 triple point and otago intermediate p thus a moderately low geother mal gradient existed 450 430 ma ago when these rocks were deformed k d fe mg actinolite fe mg chlorite values 0 52 0 70 obtained from coexisting actinolite and chlorite in metabasites from fault zones support the moderately high p c 4 kbar metamorphism suggested by the b cell parameter values the metamorphic conditions indicated by these data are contrary to the low p high t conditions pro posed by previous authors who inferred an intimate association between deformation granitoid intrusion and gold mineralization the b lattice parameter of white micas in slates adjacent to early devonian c 400 ma granitoids with schist bearing aureoles in the north eastern part of the bbz x 9 002 a n 27 s n 0 007 indicate pressures in the order of c 2 5 kbar which are in accord with those obtained from andalusite cordierite and zoisite garnet bearing assemblages observed in the higher grade metapelitic and calcareous rocks this contrasts with the higher pressure c 4 kbar existing during regional metamor phism and implies that c 6 5 8 km of metasedimentary rocks in the bbz were removed before the emplacement of the early devonian granitoids metamorphic assemblages in hornfelses associated with late devonian granitoids indicate a further 5 6 km of metasediment were removed in the next 40 ma prior to their emplacement this study shows the value of white mica studies in elucidating the tectono thermal history of a low grade metamorphic terrane dominated by metapelitic rocks

eruptive and structural history of teide volcano and rift zones of tenerife canary islands the teide and pico viejo stratocones and the northwest and northeast rifts are products of the latest eruptive phase of the island of tenerife initiated with the lateral collapse of its northern flank that formed the las canadas caldera and the icod la guancha valley ca 200 ka the eruptive and structural evolution of this volcanic complex has been reconstructed after detailed geological mapping and radioisotopic dating of the significant eruptive events a set of 54 new 14 c and k ar ages provides precise age control of the recent eruptive history of tenerife particularly teide volcano the third highest volcanic feature on earth 3718 m above sea level 7 km high and unique in terms of its intraplate setting the development of the teide pico viejo volcanoes may be related to the activity of the northwest and northeast rifts volcanic and intrusive activity along both rift zones may have played an important role in activating the gravitational landslide and in the subsequent growth nested within the collapse embayment of an increasingly higher central volcano with progressively differentiated magmas the coeval growth of the central volcano with sustained activity along the rifts led to a clear bimodal distribution in composition of eruptive products with the basaltic eruptions in the distal part of the rifts and phonolitic and more explosive eruptions in the central area where the differentiated stratocones developed current volcanic hazard in tenerife is considered to be moderate because eruptive frequency is low explosivity is modest and the eruptive activity of the teide stratocone seems to have declined over the past 30 k y with only one eruption in this period 1150 yr b p

subsidence and current strain patterns on tenerife island canary archipelago spain derived from continuous gnss time series 2008 2015 abstract in this paper we present the current crustal deformation model of tenerife island derived from daily cgps time series processing 2008 2015 our results include the position time series a global velocity estimation and the current crustal deformation on the island in terms of strain tensors we detect a measurable subsidence of 1 5 2 mm yr in the proximities of the canadas teide pico viejo ctpv complex these values are higher in the central part of the complex and could be explained by a lateral spreading of the elastic lithosphere combined with the effect of the drastic descent of the water table in the island experienced during recent decades the results show that the anaga massif is stable in both its horizontal and vertical components the strain tensor analysis shows a 70 nstrain yr e w compression in the central complex perpendicular to the 2004 sismo volcanic area and 50 nstrain yr sw ne extension towards the northeast ridge the residual velocity and strain patterns coincide with a decline in volcanic activity since the 2004 unrest

volcanic evolution of the island of tenerife canary islands in the light of new k ar data new age determinations from tenerife together with those previously published 93 in all provide a fairly comprehensive picture of the volcanic evolution of the island the oldest volcanic series with ages starting in the late miocene are formed mainly by basalts with some trachytes and phonolites which appear in anaga teno and roque del conde massifs in anaga ne three volcanic cycles occurred one older than 6 5 ma a second one between 6 5 and 4 5 ma with a possible gap between 5 4 and 4 8 ma and a late cycle around 3 6 ma in teno nw after some undated units the activity took place between 6 7 and 4 5 ma with two main series separated by a possible pause between 6 2 and 5 6 ma in the zone of roque del conde s the ages are scattered between 11 6 and 3 5 ma between 3 3 and 1 9 ma the whole island underwent a period of volcanic quiescence and erosion the large canadas volcano made up of basalts trachytes and phonolites was built essentially between 1 9 and 0 2 ma to the ne of this central volcano linking it with anaga is a chain of basaltic emission centers with a peak of activity around 0 8 ma the canadas caldera had several collapse phases associated with large ignimbrite emissions there were at least an older phase more than 1 ma old on the western part of the volcano and a younger one less than 0 6 ma old in the eastern side the two large valleys of guimar and la orotava were formed by large landslides less than 0 8 ma ago and probably before 0 6 ma ago the present canadas caldera was formed by another landslide less than 0 2 ma ago this caldera was later filled by the huge teide volcano which has been active even in historic times during the same period a series of small volcanoes erupted at scattered locations throughout the island the average eruptive rate in tenerife was 0 3 km3 ka with relatively small variations for the different eruptive periods this island and la gomera represent a model of growth by discontinuous pulses of volcanic activity separated by gaps often coinciding with episodes of destruction of the edifices and sometimes extended for several million years the neighbouring gran canaria on the other hand had an initial rapid shield building phase during which more than 90 of the island was built and a series of smaller pulses at a much later period a comparison between these three central islands indicates that the previously postulated westward displacement in time of a gap in the volcanic activity is valid only as a first approximation several gaps are present on each island overlapping in time and not clearly supporting either of the models proposed to explain the evolution of the canaries

timing of gold mineralisation in western and central victoria australia new constraints from shrimp ii analysis of zircon grains from felsic intrusive rocks abstract age constraints provided by felsic intrusive rocks indicate that gold mineralisation in western and central victoria australia occurred over a prolonged period of time ranging from prior to the late silurian to the late devonian an early phase of gold mineralisation associated with regional deformation pre dated the emplacement of late silurian felsic porphyry dykes at 413 3 ma in the central lode system of the magdala deposit stawell gold mineralisation associated with the final stages of the main regional deformation also pre dated the intrusion of early ca 400 ma to late devonian ca 370 ma plutons at stawell wonga deposit mt bute tarnagulla tallangalook maldon and heathcote in both the stawell pyrenees and ballarat metallogenic provinces consistent with preliminary dating studies of hydrothermal micas from major gold deposits later phases of gold mineralisation throughout western and central victoria were either temporally associated with or post dated the intrusion of late silurian to late devonian felsic dykes examples of this style of mineralisation include the wonga deposit at stawell mafeking fosterville maryborough minor occurrences near linton and the woods point region preliminary constraints from ballarat west indicate that late devonian dykes intruded at ca 386 ma were pervasively altered by interaction with an auriferous fluid similar to that responsible for gold deposition within the guiding star lode but that this was probably related to remobilisation during emplacement of the dykes into a pre existing mineralised structure with the exception of the woods point region and ballarat west these later phases often have a magmatic affiliation indicated by an association with cu mo bi sb and w these complex timing relationships reflect the diachronous nature of deformation metamorphism and magmatism in the western lachlan fold belt of southeast australia and suggest at least two discrete periods of gold mineralisation in the region

brine history indicated by argon krypton chlorine bromine and iodine analyses of fluid inclusions from the mississippi valley type lead fluorite barite deposits at hansonburg new mexico argon krypton chlorine bromine and iodine were measured in a homogeneous population of high salinity hydrothermal fluid inclusions from the tertiary age mississippi valley type mvt lead fluorite barite deposits at hansonburg new mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts noble gases and halogens in fluid inclusions containing 10 10 10 9 l of brine cl 3 molal were analyzed by laser microprobe noble gas mass spectrometry lmngms on neutron irradiated samples the concentrations of36ar 4 7 10 8 molal and84kr1 8 10 9 molal in the fluid inclusions are equal to those of fresh surface waters in equilibrium with air at approximately20 5 the mole ratios ofbr cl 1 2 10 4 andi cl 1 2 10 6 are among the lowest measured in any natural waters similar to those of modern brines formed by dissolution of permian nacl bearing evaporites in southeast new mexico 40ar 36ar ratios 600 are twice that of air and indicate that the fluid inclusions had excess radiogenic40ar 1 4 10 5 molal when trapped the amount of excess40ar appears to be too large to have been acquired with cl by congruent dissolution of halite bearing evaporites and possibly too small to have been acquired with pb by congruent dissolution of granitic basement rocks with proterozoic kar ages from thelmngms data combined with published pb and s isotope data we infer the following sequence of events in the history of the hansonburg mvt hydrothermal brine 1 the brine originated as relatively dilute meteoric water and it did not gain or lose atmospheric ar or kr after recharge 2 the originally dilute fluid acquired the bulk of its cl and sulfate in the subsurface after recharge by dissolving halite bearing permian marine evaporites 3 the high salinity brine then acquired most of its pb and excess radiogenic40ar from interactions with aquifer rocks other than evaporites possibly clastic sedimentary rocks or basement rocks with phanerozoic kar ages and 4 the brine deposited fluorite without having boiled or degassed

from previous c band to new x band sar systems assessment of the dinsar mapping improvement for deformation time series retrieval in urban areas we investigate the capability improvement of the advanced differential interferometric synthetic aperture radar dinsar techniques to map deformation phenomena affecting urban areas by exploiting multitemporal sar data acquired by the new x band sensors with respect to those of the previous c band systems in particular we perform a comparative analysis of the deformation time series retrieved by applying the full resolution small baseline subset dinsar technique to selected sequences of sar data acquired by the envisat and radarsat 1 sensors both operating at c band and by the x band radar systems onboard the sar sensors of the cosmo skymed csk constellation this study focused on the city of napoli italy allows us to quantify the dramatic increase of the dinsar coherent pixel density achieved by exploiting the high resolution x band csk sar images a few meters resulting in an improvement factor of about 320 and 550 with respect to the radarsat 1 and envisat products respectively this improvement permits us to analyze nearly all the structures located within the investigated urbanized area and in many cases also portions of the same building the improved coherent pixel spatial densities combined with the reduced revisit times of the new x band sar missions allow us to significantly increase the effectiveness of the advanced dinsar methodologies further extending the role of those earth observation data in the development of monitoring scenarios

deformation of basaltic shield volcanoes under cointrusive stress permutations we performed a microstructural study of piton des neiges la reunion island to understand how intrusions and stresses control each other in basaltic volcanoes our study reveals that three perpendicular intrusions trends coexisted during the 2 myr history of the volcano a n120 140 e rift zone a perpendicular dike trend and swarms of subhorizontal intrusions hereafter called sill zones independently the inversion of fault slip data shows that incompatible paleostress fields recurrently occurred along with the intrusions a dominant nne ssw extension a perpendicular extension and strike slip or compressional regimes the orientations of paleostresses are consistent with the orientations of the three perpendicular intrusion populations we propose that stress accumulation in the edifice under the effect of repeated magma injections resulted in permutations of the principal axes of the stress tensor causing a reorientation of subsequent intrusions stress permutations were cyclical each cycle started with dike injections in an extensional stress field reducing the deviatoric stress and switching the axes of principal stresses and finished with sill intrusions in a compressional stress field sill zones acted as detachment planes restoring the extensional stress field and initiating a new cycle of permutations our model of stress permutations is in agreement with the pattern of eruptions and deformation observed at piton de la fournaise in contrast with the hawaiian model of spreading on a decollement stress permutations in la reunion s volcanoes imply that the basal deformation of the edifices if any is not sufficient to compensate the reduction of deviatoric stress caused by intrusions

gravity constraints on the structure and volcanic evolution of tenerife canary islands a detailed gravity study of tenerife constrains the internal structure of the island and its active magma system the maximum bouguer anomaly 2636 gu 1 gu 10 6 m s 2 0 1 mgal occurs over the sw part of the postshield las canadas edifice lce while smaller highs occur over the eroded shield volcanoes the main high extends ne and nw over the adjacent dorsal and santiago rift zones a deep low occurs over the northern lce and teide volcano the power spectrum of the anomalies suggests shallow causative structures 3 km inferred to belong to the island s dense core a model computed from the anomalies uses core and carapace densities of 2900 and 2360 kg m 3 respectively except beneath the main high where the core requires a higher density 3210 kg m 3 this part of the body is interpreted as a buried mafic volcano of substantial size the boca tauce volcano containing an old mafic plutonic complex the enigmatic las canadas caldera that truncates the lce shows strong asymmetry dense materials occupy the southern part whereas low density materials occupy the northern part to 2 3 km depth consistent with a vertical collapse origin high density materials in the south are related to the intracaldera extension of the dorsal rift zone the boundary between subcaldera domains is interpreted as the buried head of the giant icod landslide valley the icod landslide appears to have modified the caldera truncating its northern side and to have subsequently controlled the location of the active pico teide pico viejo vent systems voluminous chaotic deposits lying off northern tenerife previously associated with the formation of the caldera and icod valley are better interpreted as being derived from older mass wasting events the southern lce has been buttressed against lateral failure by the buried boca tauce volcano

shallow structure beneath the central volcanic complex of tenerife from new gravity data implications for its evolution and recent reactivation abstract we present a new local bouguer anomaly map of the central volcanic complex cvc of tenerife spain constructed from the amalgamation of 323 new high precision gravity measurements with existing gravity data from 361 observations the new anomaly map images the high density core of the cvc and the pronounced gravity low centred in the las canadas caldera in greater detail than previously available mathematical construction of a sub surface model from the local anomaly data employing a 3d inversion based on growing the sub surface density distribution via the aggregation of cells enables mapping of the shallow structure beneath the complex giving unprecedented insights into the sub surface architecture we find the resultant density distribution in agreement with geological and other geophysical data the modelled sub surface structure supports a vertical collapse origin of the caldera and maps the headwall of the ca 180 ka icod landslide which appears to lie buried beneath the pico viejo pico teide stratovolcanic complex the results allow us to put into context the recorded ground deformation and gravity changes at the cvc during its reactivation in spring 2004 in relation to its dominant structural building blocks for example the areas undergoing the most significant changes at depth in recent years are underlain by low density material and are aligned along long standing structural entities which have shaped this volcanic ocean island over the past few million years

error estimation in multitemporal insar deformation time series with application to lanzarote canary islands 1 interferometric synthetic aperture radar insar is a reliable technique for measuring crustal deformation however despite its long application in geophysical problems its error estimation has been largely overlooked currently the largest problem with insar is still the atmospheric propagation errors which is why multitemporal interferometric techniques have been successfully developed using a series of interferograms however none of the standard multitemporal interferometric techniques namely ps or sb persistent scatterers and small baselines respectively provide an estimate of their precision here we present a method to compute reliable estimates of the precision of the deformation time series we implement it for the sb multitemporal interferometric technique a favorable technique for natural terrains the most usual target of geophysical applications we describe the method that uses a properly weighted scheme that allows us to compute estimates for all interferogram pixels enhanced by a montecarlo resampling technique that properly propagates the interferogram errors variance covariances into the unknown parameters estimated errors for the displacements we apply the multitemporal error estimation method to lanzarote island canary islands where no active magmatic activity has been reported in the last decades we detect deformation around timanfaya volcano lengthening of line of sight subsidence where the last eruption in 1730 1736 occurred deformation closely follows the surface temperature anomalies indicating that magma crystallization cooling and contraction of the 300 year shallow magmatic body under timanfaya volcano is still ongoing

halogen concentrations in pore waters and sediments of the nankai trough japan implications for the origin of gas hydrates abstract presented here are halogen concentrations cl br and i in pore waters and sediments from three deep cores in gas hydrate fields of the nankai trough area the three cores were drilled between 1999 and 2004 in different geologic regions of the northeastern nankai trough hydrate zone iodine concentrations in all three cores increase rapidly with depth from seawater concentrations 0 00043 mmol l to values of up to 0 45 mmol l the chemical form of i was identified as i in accordance with the anaerobic conditions in marine sediments below the so 4 reduction depth the increase in i is accompanied by a parallel although lesser increase in br concentrations while cl concentrations are close to seawater values throughout most of the profiles large concentration fluctuations of the three halogens in pore waters were found close to the lower boundary of the hydrate stability zone related to processes of formation and dissociation of hydrates in this zone generally low concentrations of i and br in sediments and the lack of correlation between sediment and pore water profiles speak against derivation of i and br from local sediments and suggest transport of halogen rich fluids into the gas hydrate fields differences in the concentration profiles between the three cores indicate that modes of transportation shifted from an essentially vertical pattern in a sedimentary basin location to more horizontal patterns in accretionary ridge settings because of the close association between organic material and i and the similarity of transport behavior for i and ch 4 the results suggest that the ch 4 in the gas hydrates also was transported by aqueous fluids from older sediments into the present layers

link between gold provinces low salinity high temperature 200 degrees c reducing fluids are poorly represented in ore forming processes yet appear to account for 90 percent of the primary gold mined to date such fluids have been implicated in the formation of many archcan greenstone witwatersrand slate belt and epithermal gold deposits these low salinity auriferous fluids occur in variable time space lithological sequence and tectonic settings and are most easily explained by metamorphic devolatilization of mafic and or graywacke successions metamorphism of chlorite calcite albite quartz assemblages e g mafic or graywacke at the greenschist amphibolite facies boundary occurs around 480 degrees or 20 degrees c for 3 5 kbars and produces large volumes of low salinity h 2 o co 2 fluid similar in composition to those recorded in many gold deposits widespread pyrite in the above assemblage typically leads to elevated levels of dissolved sulfur such conditions are ideal for gold transport as a molecular au s complex and can lead to deposits rich in gold relative to silver and base metals deposition of gold occurs in the temperature range of 250 degrees to 400 degrees c and can be facilitated by lower temperature lower sulfur activity and changes in oxygen activity lower sulfur activity is most readily achieved by fluid interaction with fe rich host rocks with the formation of pyrite or pyrrhotite whereas lower oxygen activity is readily achieved by interaction with carbonaceous metasediments low salinity fluids produced by metamorphic devolatilization provide a common theme embracing the formation of many archcan greenstone slate belt witwatersrand and potentially epithermal gold deposits it involves the common features of high geothermal gradient low salinity fluid high au ag high au base metals and broad synchroneity with metamorphism it also accounts for the considerable variability in hosting structures detailed timing relations host rocks alteration assemblages and geologic age of different deposits interestingly the similarities are explained by deeper processes the differences by processes at or near the depositional sites

the geology and gold deposits of the victorian gold province abstract the palaeozoic succession of victoria represents a major world gold province with a total production of 2500 t of gold i e 78 million oz on a global scale central victoria represents one of the most gold mineralized areas outside the witwatersrand of south africa and remains the prime example of a slate belt gold province also known as turbidite hosted or shale greywacke gold province production came from quartz veins 1000 t modern placers 1200 t and palaeoplacers 300 t up to 7000 mines produced gold from quartz veins however the 168 mines of this type which produced over 1 t au contributed 68 of the primary gold production twelve goldfields have each produced 30 t au approximately one million ounces from all sources with bendigo 697 t ballarat 408 t and castlemaine 173 t being the largest these twelve goldfields have contributed 71 of the combined primary and secondary production gold mining commenced in 1851 declined dramatically around 1914 and has not increased significantly since the palaeozoic succession of victoria is part of an extensive fold belt along much of eastern australia i e the tasman orogenic belt in victoria the succession is dominated by cambrian to early devonian clastic metasedimentary rocks that have undergone major upright deformation and low grade metamorphism culminating in the middle devonian tabberabberan orogeny north south inliers of cambrian metavolcanic and metasedimentary rocks associated with regional fault zones divide the province into several geologically distinct zones in central victoria there are particularly well developed acid volcanic complexes of late devonian age and synchronous peraluminous granites which represent high temperature crustal melting tertiary to quaternary basalts have covered some of the palaeozoic gold deposits and have also covered several rich gold placer deposits of cainozoic age larger goldfields including bendigo and ballarat occur in ordovician slate and greywacke sequences but a wide range of metamorphosed sedimentary and igneous rock types are host to goldfields most if not all primary deposits demonstrate structural control although the controlling structural features differ between deposits wallrock alteration is strongly influenced by host rock in metasedimentary rocks it is limited and subtle but it is more pervasive in mafic and felsic igneous rocks carbonates muscovite and pyrite are the most widespread alteration minerals in these rocks representing co 2 k and s addition enrichment of as within gold deposits is common with sb important in some small deposits whereas base metals are only abundant locally and bi w mo and te show strong spatial association with granites and are rarely associated with economic gold deposits granites are an important component of the palaeozoic succession in victoria no large deposits are within granites but a few goldfields including maldon 65 t au are within contact aureoles of either s or i type granites of differing degrees of fractionation and silica content a single stage but protracted and possibly diachronous period of gold introduction near the time of the middle devonian tabberabberan deformation can explain geological relationships at many gold deposits the possibility that this event was slightly older i e silurian or early devonian in the west of the state cannot be precluded from the available evidence the mineralizing event appears linked to the same thermal event as diorite lamprophyre dykes and graite intrusions acidic and basaltic volcanism deformation and regional metamorphism the limited amount of fluid chemistry data from victorian gold deposits suggests low salinity fluids which contained co 2 and variable methane with homogenization temperatures from 150 to 300 c the sulphur isotopic compositions of pyrite are mostly 1 to 5 with some values slightly above 10 mineralizing temperatures are inferred to be near 300 c and pressure around 1 2 kbar sulphide rich gold deposits in the east of victoria many of which contain significant base metals contrast with the rest of the province which contains mostly gold deposits with lower sulphide content and this eastern area should possibly be viewed as separate from the victorian gold province per se the benefits to victorian gold mining coming from the 1980 s global gold boom have been insignificant compared to the historical importance of the victorian gold province there seems little justification for assuming that all the large deposits have been discovered and there is reason to believe new deposit styles may emerge to complement the limited current exploration activity which is focussed on the search for extensions and repeats of known deposit types a major advance in scientific understanding of these oft neglected deposits could kindle a major exploration and production revival

detection of displacements on tenerife island canaries using radar interferometry tenerife is one of the most well monitored islands of the canaries but the surveillance generally is centred on las canadas caldera where the teide volcano is located in the last 180 000 yr the eruptions on tenerife island have never occurred in the same volcanic structure except for the teide and pico viejo central volcanic system so that a complete monitoring network would have to cover the whole island as a result synthetic aperture radar interferometry insar is being used on tenerife because this space technique can provide a displacement map of the surface of the earth with centimetre precision this paper presents the results obtained on tenerife island using 18 sar images acquired by the ers 1 and ers 2 satellites during the period 1992 2000 two important results have been obtained no deformation on las canadas caldera coinciding with results obtained using terrestrial techniques and two subsidence episodes outside monitoring areas in the nw of the island in the region of the last historic eruptions these results show that insar is a useful technique for monitoring the entire island thus allowing us to discover deformations in areas that are not routinely or easily monitored this technique has been used in combination with global positioning system gps observation of a global network on the island to define a new geodetic monitoring system the possible causes of the deformations observed have been studied in an endeavour to discern if they might be of natural origin in particular linked to a reactivation of prior volcanic activity examination of the geophysical observations on the island human activities underway and the results of the modelling seem to indicate that at least part of the deformations may be caused by changes in the groundwater level and therefore are not linked to a volcanic reactivation this result is important because it implies that if geodetic volcano monitoring is to be performed on the island the system used must be capable of discerning between various possible origins of the deformation by analysing their patterns and ancillary information from other sources in this regard insar is a basic tool on account of its unpaired wide area coverage and spatial density

metamorphism in archaean greenstone belts calculated fluid compositions and implications for gold mineralization an inescapable consequence of the metamorphism of greenstone belt sequences is the release of a large volume of metamorphic fluid of low salinity with chemical characteristics controlled by the mineral assemblages involved in the devolatilization reactions for mafic and ultramafic sequences the composition of fluids released at upper greenschist to lower amphibolite facies conditions for the necessary relatively hot geotherm corresponds to those inferred for greenstone gold deposits xco2 0 2 0 3 this result follows from the calculation of mineral equilibria in the model system cao mgo feo al2o3 sio2 h2o co2 using a new expanded internally consistent dataset greenstone metamorphism cannot have involved much crustal over thickening because very shallow levels of greenstone belts are preserved such orogeny can be accounted for if compressive deformation of the crust is accompanied by thinning of the mantle lithosphere in this case the observed metamorphism which was contemporaneous with deformation is of the low p high t type for this type of metamorphism the metamorphic peak should have occurred earlier at deeper levels in the crust i e the piezothermal array should be of the deeper earlier type however at shallow crustal levels the piezothermal array is likely to have been of deeper later type as a consequence of erosion thus while the lower crust reached maximum temperatures and partially melted to produce the observed granites mid crustal levels were releasing fluids prograde into shallow crustal levels that were already retrograde we propose that these fluids are responsible for the gold mineralization thus the contemporaneity of igneous activity and gold mineralization is a natural consequence of the thermal evolution and does not mean that the mineralization has to be a consequence of igneous processes upward migration of metamorphic fluid via appropriate structurally controlled pathways will bring the fluid into contact with mineral assemblages that have equilibrated with a fluid with significantly lower xco2 these assemblages are therefore grossly out of equilibrium with the fluid in the case of infiltrated metabasic rocks intense carbonation and sulphidation is predicted if as seems reasonable gold is mobilized by the fluid generated by devolatilization then the combination of processes proposed most of which are an inevitable consequence of the metamorphism leads to the formation of greenstone gold deposits predominantly from metamorphic fluids

an overview of geodetic volcano research in the canary islands the canary islands are mostly characterized by diffuse and scattered volcanism affecting a large area with only one active stratovolcano the teide pico viejo complex tenerife more than 2 million people live and work in the 7 447 km2 of the archipelago resulting in an average population density three times greater than the rest of spain this fact together with the growth of exposure during the past 40 years increases volcanic risk with respect previous eruptions as witnessed during the recent 2011 2012 el hierro submarine eruption therefore in addition to purely scientific reasons there are economic and population security reasons for developing and maintaining an efficient volcano monitoring system in this scenario geodetic monitoring represents an important part of the monitoring system we describe volcano geodetic monitoring research carried out in the canary islands and the results obtained we consider for each epoch the two main existing constraints the level of volcanic activity in the archipelago and the limitations of the techniques available at the time theoretical and observational aspects are considered as well as the implications for operational volcano surveillance current challenges of and future perspectives in geodetic volcano monitoring in the canaries are also presented

bromine and iodine in peru margin sediments and pore fluids implications for fluid origins at the peruvian convergent margin two distinct pore fluid regimes are recognized from differences in their cl concentrations the slope pore fluids are characterized by low cl concentrations but elevated br and i concentrations due to biogenic production the shelf pore fluids exhibit elevated cl and br concentrations due to diffusive mixing with an evaporitic brine in the slope pore fluids the br i and nh4 concentrations are elevated following bacterial decomposition of organic matter but the i concentrations are in excess of those expected based on mass balance calculations using nh4 and br concentrations the slope sediment organic matter which is enriched in iodine from oxidationreduction processes at the oxygenated sediment water interface is responsible for this enrichment the increases in dissolved i and the i enrichments relative to nh4 and br correlate well with sedimentation rates because of differential trapping following regeneration the pore fluid i br ratios suggest that membrane ion fiitration is not a major cause of the decreases in cl concentrations other possible sources for low cl water including meteoric water clathrate dissociation and or mineral dehydration reactions imply that the diluting component of the slope low cl fluids has flowed at least 1 km through the sediment the low bottom water oxygenation in the shelf is responsible for the low if any enrichment of iodine in the shelf sediments fluctuations in bottom water oxygen concentrations in the past however may be responsible for the observed variations in the sediment ibr ratios comparison of na cl and br cl molar ratios in the pore fluids shows that the shelf high cl fluid formed from mixing with a brine that formed from seawater concentrated by twelve to nineteen times and probably was modified by halite dissolution this dense brine located below the sediment sections drilled appears to have flowed a distance 500 km through the sediment

character and kinematics of faults within the turbidite dominated lachlan orogen implications for tectonic evolution of eastern australia reply fault zones within turbidite dominated orogenic systems typified by the lachlan orogen of eastern australia are characterised by higher than average strain and intense mica fabrics transposition foliation and isoclinal folds poly deformation with overprinting crenulation cleavages and steeply to moderately plunging meso and micro folds they have a different character compared to the brittle ductile fault zones of classic foreland fold and thrust belts such as the appalachians and the canadian rocky mountains multiple cleavages and transposition layering record a progressive shear related deformation history an intense mica fabric evolves initially during shortening of the overlying sedimentary wedge but is progressively modified during rotation and emplacement to higher structural levels along the steep parts of inferred listric faults the deformed wedge outside the fault zones generally undergoes one phase of deformation shown by a weak to moderately developed slaty cleavage which is parallel to the axial surface of upright subhorizontally plunging chevron folds other faults within the turbidites of the lachlan orogen include the steep zones of ductile strike slip deformation that bound a centrally located high t low p metamorphic complex characterised by s c mylonites these ductile shear zones indicate a southward passage of the metamorphic complex as a crustal wedge with emplacement to higher structural levels along a leading edge ductile thrust fault ar ar dating constrains the timing of regional deformation to be mostly late ordovician through silurian across the lachlan orogen faults in the low grade turbidite sequences record the kinematic evolution of the developing lachlan orogen and indicate progressive deformation associated with simultaneous eastward propagating and migrating deformation fronts in both the western and eastern parts of the fold belt these deformation fronts are related to accretionary style deformation at the leading edges of overriding plates in an inferred southwest pacific type subduction setting from the late ordovician to the mid devonian along the former gondwana margin the fault zones effectively accommodate and preserve movements within the structurally thickening migrating and prograding accretionary wedge

round hill shear zone hosted gold deposit macraes flat otago new zealand evidence of a magmatic ore fluid the 0 8 moz round hill shear zone hosted gold deposit is one of several located on or near the hyde macraes shear zone macraes flat new zealand field relationships show stockwork veins are the oldest part of the hydrothermal system followed by flat and ramp veins hanging wall shear veins formed early but have been modified by late deformation fluid inclusion microthermometric results for dominant type i inclusions show that flat and ramp veins have the same average wt percent nacl equiv values 2 2 0 6 and were precipitated from the same fluid salinity data for these veins overlap with those from hanging wall veins average 1 3 0 3 and stockwork veins 1 6 0 6 for vein margins 0 9 0 3 for vein centers although both of the latter trend toward lower overall wt percent nacl equiv values suggesting mixing between relatively dilute and more saline end members all of the above veins have similar temperatures of homogenization t h ranging between 110 and 188 c fluid inclusion trapping temperatures are considered to be 300 c equating to a 10 km depth of formation carbon dioxide dissolved in the hydrothermal fluid is responsible for up to one third of fluid inclusion apparent salinities stockwork and hanging wall veins thus have true salinities of 1 wt percent nacl equiv 0 17 molal and flat and ramp veins have true salinities of fluid inclusion volatiles from round hill and other macraes deposits are dominated by h 2 o 99 02 99 69 mol with lesser co 2 0 14 0 76 mol n 2 0 03 0 32 mol and ch 4 0 06 0 17 mol noticeable concentrations of hydrocarbons occur in many of the samples fluid inclusion cation and anion data show few components of relatively low concentration are dissolved in the hydrothermal fluid consistent with co 2 corrected microthermometric measurements a range in fluid inclusion d h 2 o values obtained for the round hill deposit is coincident with the different vein types and also indicates mixing between two fluids one fluid is considered to be o isotope shifted meteoric water as trapped by the early stockwork veins and has the lowest d h 2 o values of 80 per mil the other fluid is represented by flat and or ramp and hanging wall veins that have d h 2 o values up to 40 per mil the macraes d h 2 o data show a trend toward the magmatic water end member for geothermal systems associated with convergent plate boundaries and are consistent with a 25 to 50 percent magmatic component in the macraes hydrothermal system

chronology and tectonic framework of turbidite hosted gold deposits in the western lachlan fold belt victoria results abstract 40 ar 39 ar data constrain the history of metamorphism deformation and mineralization in the western subprovince of the lachlan fold belt rocks in the mount stavely volcanic complex and the bushy creek pluton give 40 ar 39 ar ages of about 500 ma for hornblende and biotite the dates from the mount stavely volcanic complex limit the age of mineralization in the metavolcanic rocks of the stavely belt whereas the date for the bushy creek pluton extends the area of cambrian ordovician plutons of the delamerian orogeny to east of the grampians mountains and helps define the surface expression of the western border of the paleozoic lachlan fold belt 40 ar 39 ar dating of metamorphic mica growth phengite in cleaved slates and phyllites within the landsborough fault avoca fault zone heathcote fault zone and mount wellington fault zone gives ages of 453 2 440 2 426 4 and 410 390 ma respectively these data indicate a progression of deformation from west to east starting in late ordovician early silurian time in the stawell and bendigo ballarat structural zones the major phase of deformation in the western subprovince of the lachlan fold belt is therefore silurian and not devonian sericites from major gold deposits in the stawell zone and bendigo ballarat zone give 40 ar 39 ar dates of about 440 ma that are coincident with folding and thrusting a second episode of mineralization and fault reactivation at about 420 to 410 ma is found in some deposits in these zones based on data from a previous study in the melbourne zone including the woods point dike swarm and locally in the bendigo ballarat zone some gold deposits give sericite dates of about 380 360 ma these ages are consistent with the close association of many melbourne zone gold deposits with devonian dikes and plutons the results indicate that gold mineralization in the stawell zone bendigo ballarat zone and melbourne zone was episodic and both temporally and spatially associated with crustal heating linked to regional metamorphism and plutonism initial stages of mineralization in the province comprising many of the large deposits in western and central victoria e g bendigo ballarat stawell wattle gully tarnagulla accompanied metamorphism folding and thrusting subsequent mineralization is widespread but produced mainly smaller deposits

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

the distribution of basaltic volcanism on tenerife canary islands implications on the origin and dynamics of the rift systems abstract one of the most characteristic features of volcanic islands is the existence of rift zones defined commonly as orientated eruptive fissures or parallel rows of elongate cinder cones and dyke swarms occasionally these rifts can appear at the birth of the volcanic island and persist until the last episodes of its constructions controlling the form and structure of the island e g azores islands in the case of tenerife canary islands it is possible to observe two rift zones santiago del teide and dorsal rifts running nw se and ene wsw marked by parallel rows of aligned cones and eruptive fissures additionally at the southern part of the island southern volcanic zone basaltic volcanism is characterized by scattered vents and apparently non coherently orientated eruptive fissures some authors relate the existence of the latter volcanism to a n s running rift zone that defines the third branch of a three armed rift system in the island in the present paper we first investigate the tectonic controls on the distribution of basaltic volcanism at the southern volcanic zone and their relation with the nw se and ene wsw rifts the numerical results obtained suggest that basaltic volcanism of the southern part of tenerife can be easily explained as the result of a extensional stress field derived from the combined effects of the nw se and ene wsw rifts as a second objective we have also investigated the origin of the santiago del teide and dorsal rift zones and their role on the formation of the original shield volcano and the subsequent evolution of the whole island our numerical results contrast with previously published explanations on the origin of the tenerife rifts that included fracturing due to volcano spreading or to deformation of the volcano due to magma intrusion we consider that volcanic activity in tenerife began throughout fissural volcanism along these structures that were already present in the oceanic basement progressively accumulating the basaltic series that gave rise to the construction of the composite shield volcano

spatiotemporal analysis and interpretation of 1993 2013 ground deformation at campi flegrei italy observed by advanced dinsar campi flegrei is one of the most hazardous volcanic areas in the world because of its close proximity to the city of naples here we apply the multidimensional small baseline subset msbas differential interferometric synthetic aperture radar dinsar technique to obtain vertical and horizontal components of ground deformation for campi flegrei at high spatial and temporal resolutions that span for the first time 20 years the area underwent continuous subsidence from 1993 through 1999 moderate uplift began in 2010 and substantially increased through 2012 reaching approximately 13 cm by 2013 we model the observed deformation to determine source parameters for subsidence and uplift epochs both the inflation and deflation mechanisms involve large extended sources in a layered hydrothermal system whose location is controlled by the caldera structure and stratigraphy the temporal resolution of msbas approaches that of gps daily time series with superior precision and spatial resolution making it an excellent alternative for volcano monitoring

radar interferometry techniques for the study of ground subsidence phenomena a review of practical issues through cases in spain subsidence related to multiple natural and human induced processes affects an increasing number of areas worldwide although this phenomenon may involve surface deformation with 3d displacement components negative vertical movement either progressive or episodic tends to dominate over the last decades differential sar interferometry dinsar has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas this work discusses the main advantages and limitations of addressing active subsidence phenomena by means of dinsar techniques from an end user point of view special attention is paid to the spatial and temporal resolution the precision of the measurements and the usefulness of the data the presented analysis is focused on dinsar results exploitation of various ground subsidence phenomena groundwater withdrawal soil compaction mining subsidence evaporite dissolution subsidence and volcanic deformation with different displacement patterns in a selection of subsidence areas in spain finally a cost comparative study is performed for the different techniques applied

pressure fluctuations phase separation and gold precipitation during seismic fracture propagation gold mineralization at croagh patrick western ireland occurs in quartz veins associated with three synchronous oblique tensile shear systems the veins evolved by progressive thickening of isolated en echelon lensoid tensile fractures that show a power law relation between their length and thickness a change in power law exponent marks the linking of the en echelon arrays by large oblique tensile veins fluid inclusion data show that gold was deposited due to unmixing of an h 2 o co 2 nacl fluid at 320 240 c and 160 30 mpa primarily due to decreases in fluid pressure evidence for phase separation is only observed in the large linking veins and is abundant close to intersections of the vein arrays these sites are where high gold grades occur the distribution of gold is believed to reflect both spatial and temporal variations in fluid pressure fluctuation during seismic fracture propagation controlled by the vein growth mechanism and zones of maximum dilation

new geodetic monitoring system in the volcanic island of tenerife canaries spain combination of insar and gps techniques even though volcanic activity in tenerife is characterized by the fact that eruptions do not normally occur more than once in the same volcanic edifice geodetic monitoring has mainly focused on the las canadas caldera where a geodetic micronetwork and a levelling profile are located a sensitivity test of this geodetic network showed a clear need to extend it to cover the full island for volcano monitoring purposes this conclusion together with the detection of two unexpected movements on the island using insar that were beyond the scope of the traditional geodetic network prompted the authors to design and observe a gps network covering the whole of tenerife the network was monitored in august 2000 the results obtained were accurate to 1 cm and confirm the deformation in the pinar de chio zone but are not definitive enough to confirm the displacements detected to the south of the village of garachico furthermore new cases of possible subsidence have been detected in areas where insar could not be used to measure deformation due to low coherence future observations will be necessary for further validation and to study the time evolution of the displacements and supplementary research must be conducted to determine the possible causes in particular if they are connected with the water pumping operations performed on the island one important result is that a new geodetic monitoring system based on two complementary techniques insar and gps has been set up on tenerife island this is the first time that the whole surface of any of the volcanic canary islands has been covered with a single network this research has displayed the need for further similar studies in the canary islands at least on the islands which pose a greater risk of volcanic reactivation

buttressing and fractional spreading of tenerife an experimental approach on the formation of rift zones 1 the island of tenerife is composed of three miocene shields which are centered by the canadas volcano since the pliocene tenerife sits on more than 2 km thick oceanic sediments quaternary volcanism of the canadas series and giant landslides were principally confined to triaxial rift zones the mechanism of triaxial rifting however has remained unclear physical analog models show that these rift zones may have formed by gravity driven lateral escape of island segments induced by loading of the deformable substratum for experiments scaled to tenerife three adjacent sand cones were mounted onto viscous pdms substratum gravitational spreading caused circumferential expansion of each cone until a large edifice canadas was constructed in their center the older cones now acted each as a buttress radial fractures were overprinted by fractional spreading of the canadas edifice this resulted in formation of three main extensional zones resembling the triaxial rifting configuration of tenerife

mid crustal fluid mixing in a proterozoic fe oxide cu au deposit ernest henry australia evidence from ar kr xe cl br and i fluid inclusions in six quartz veins associated with cu au mineralisation at the giant ernest henry iron oxide copper gold deposit 167 mt 1 1 cu 0 54 ppm au in northwest queensland have been analysed for naturally occurring and neutron produced noble gas isotopes of ar kr and xe a combination of thermal and mechanical decrepitation methods enables distinction between four types of fluid inclusion ultra high salinity 30 to 70 wt nacl eq fluid inclusions have compositions that define two end members that are variably mixed in different samples the first end member has a 40 ar 36 ar value of 29 000 a 40 are cl value of 3 10 3 and mantle like br cl and i cl values of 1 2 10 3 and 11 10 6 respectively the second end member has a much lower 40 ar 36 ar value of less than 2500 a 40 are cl value of 10 6 low br cl values of 0 4 10 3 and i cl values of 1 2 10 6 all ratios are molar carbon dioxide and later lower salinity liquid vapour fluid inclusions have similar 40 ar 36 ar values of less than 2500 in all samples these data are compatible with genetic models in which cu au mineralisation formed at a depth of 6 10 km from circulation of magmatic fluids derived from regionally abundant a type granites and a high salinity halite dissolution brine generated from sedimentary formation waters in the upper crust the largest source of co2 was probably carbonate rich lithologies in the midcrust later lower salinity fluids with a surficial origin diluted the mineralising brines and are preserved in the latest secondary fluid inclusions these data provide insight on the composition of crustal fluids during the proterozoic furthermore the magmatic fluid endmember derived from melts generated by re melting lower crustal paleoproterozoic igneous rocks with a mantle source preserves mantle like br cl and i cl these geochemical characteristics are interpreted to provide insight on i recycling at subduction zones and the composition of seawater in the paleoproterozoic 2007 elsevier b v all rights reserved

a new gravity inversion method for multiple subhorizontal discontinuity interfaces and shallow basins 1 we present a method for 3 d gravity inversion designed to obtain density contrast models described by subhorizontal layers limited by irregular discontinuity interfaces and models constituted by shallow basins with light infill it is based on a previously published inversion method that provides in a nearly automatic approach the 3 d geometry of isolated anomalous bodies the basic adjustment constraints are model fitness fitting the anomaly data and model smoothness minimizing the total anomalous mass for models corresponding to subhorizontal layers we consider an additional minimization condition the proximity to prescribed horizontal interfaces this condition is arranged by including an additional weighting inverse proportional to the distance to the interface in the covariance matrix for model parameters the approach works according a growth process that increases step by step the volume of the adjusted anomalous bodies some advantages of the method are simultaneous adjustment of a linear regional gravity trend possibility of including simultaneously positive and negative anomalous structures in the model and unified inversion approach for isolated bodies basins and subhorizontal interface structures we include several simulation examples and an application case layered model for the volcanic island of tenerife

a geochronological framework for orogenic gold mineralisation in central victoria australia new 40ar 39ar geochronological data support and significantly expand upon preliminary age data that were interpreted to suggest an episodic and diachronous emplacement of gold across the western lachlan fold belt australia these geochronological data indicate that mineralisation in the central victorian gold province occurred in response to episodic eastward progressing deformation metamorphism and exhumation associated with the formation of the western lachlan fold belt initial gold formation throughout the stawell and the bendigo structural zones can be constrained to a broad interval of time between 455 and 435 ma with remobilisation of metals into new structures and or new pulses of mineralisation occurring between 420 and 400 ma and again between 380 and 370 ma linked to episodic variations in the regional stress field and during intrusion of felsic dykes and plutons this separation of ages is incompatible with the view that gold emplacement in the western lachlan fold belt was the result of a single orogen wide event during the devonian a distinct phase of gold mineralisation characterised by elevated cu mo sb or w is associated with both late silurian to early devonian 420 to 400 ma and middle to late devonian 380 to 370 ma magmatism when crustal thickening and shortening during the ongoing consolidation of the western lachlan fold belt led to extensive melt development in the lower crust and resulted in widespread magmatism throughout central victoria these 420 to 400 ma and 380 to 370 ma occurrences best exemplified by the wonga deposit in the stawell structural zone and many of the woods point deposits in the melbourne structural zone but also evidenced by occurrences at fosterville and maldon in the bendigo structural zone clearly formed synchronous with or post date the emplacement of plutons and dykes and thus are spatially if not genetically related to melt generation at depth this later magmatic associated and polymetallic type of gold mineralisation is economically subordinate to the earlier metamorphic associated type of gold deposition in the stawell and bendigo structural zones but tends to be the dominant style in the melbourne zone these new geochronological constraints together with zircon u pb data from felsic intrusive rocks of known relationship to gold mineralisation demonstrate that initial hydrothermal alteration associated with gold emplacement in the western lachlan fold belt was metamorphic related predating the emplacement of granite plutons by as much as 80 million years this timing differs from other important orogenic gold districts where gold deposition is closely associated spatially with felsic magmatism the early introduction of metamorphically derived fluids well before magmatism may reflect variations in the timing of peak metamorphic conditions at different crustal levels in an accretionary prism undergoing simultaneous deformation and erosion consequently no genetic link exists between the main phase s of gold mineralisation and magmatism in the central victorian gold province with the exception of formation of a minor magmatism related and geochemically distinct mineralisation style at about 420 to 400 ma and again at about 380 to 370 ma the apparent spatial relationship between gold mineralisation and felsic intrusions is merely the result of melts and fluids being channelised along the same structures

internal architecture of la reunion indian ocean inferred from geophysical data the internal structure of la reunion indian ocean is investigated using gravity magnetic and electromagnetic data a general model of the island is derived providing new information on the individual volcanoes as well as on the growth of the island as a whole the reconstructed topography of the island at 780 ka brunhes matuyama magnetic reversal shows a paleo island organized around a huge piton des neiges volcano and a smaller les alizes volcano both having large offshore extensions and dense hypovolcanic complexes during the brunhes period the piton des neiges has growth predominantly in its central and west southwest areas and to a less extent to the north the construction of piton de la fournaise at the east has caused the other major change in the topography of the island this latter volcano the youngest and the smallest of the three identified volcanoes of la reunion only achieves a large thickness beneath its central and southern zones the resistivity and magnetic patterns of its central area support the presence of a hydrothermal system in its western older part shallow highly resistive and dense layers are interpreted as piles of thick lava flows filling paleo depressions in the same area a deep dense body may represent the hypovolcanic intrusive complex from the early stages of piton de la fournaise piton des neiges is by far the largest volcano of la reunion the resistivity data show that its products are more altered than those of piton de la fournaise a hydrothermal alteration is particularly developed around the dense central hypovolcanic intrusive complex this latter characterized by resistive and dense terrains has a lateral extent that coincides with that of the overlying topographic depressions the three central cirques the bebour belouve depression and at its eastern tip the plaine des palmistes a genetic link between the morphology of the volcano and a possible subsidence of the dense complex is investigated but no definitive conclusion is reached the offshore part and the hypovolcanic complex of les alizes volcano have been described by previous works here we identified the reversely magnetized terrains beneath piton de la fournaise with at least part of the construction of les alizes volcano but no geophysical contrast marking at depth the boundary between piton de la fournaise and les alizes is recognized suggesting that the products of both volcanoes are lithologically similar at the scale of our work

two shell ionospheric model for indian region a novel approach in the u s wide area augmentation system european geostationary navigation overlay service and indian global positioning system aided geo augmented navigation a near real time grid based single shell model is proposed to correct the ionospheric delay at the user aircrafts the single shell model is based on the assumption that the whole ionosphere is compressed at a fixed altitude at 350 km this assumption may not be appropriate for the indian region which falls in the equatorial ionospheric anomaly belt in this paper a two shell model which incorporates two different shells at 300 and 500 km altitudes having different weights at different time domains has been implemented a statistical comparison between single and two shell models has been done for all quiet days of year 2005 based on the results it is observed that there is at least 60 improvement in the performance of the two shell model in comparison to the single shell model for the indian region

cl br ratios and stable chlorine isotope analysis of magmatic hydrothermal fluid inclusions from butte montana and bingham canyon utah a bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry cu deposits in butte montana usa and bingham canyon utah usa the leachates mostly represent low salinity magmatic hydrothermal fluid inclusions their halogen ratios br cl of fluid inclusion leachates were determined by ion chromatography and 37cl values of the leachates were measured by continuous flow isotope ratio mass spectrometry br cl ratios from early pre main stage and later main stage veins at butte range from 0 60 to 1 88 10 3 m ratios are similar in pre main stage veins with sericite bearing selvages and main stage samples ranging from 0 81 to 1 08 10 3 and from 0 92 to 1 88 10 3 m respectively clustering below seawater 1 54 10 3 m and overlapping mantle values 1 2 10 3 m two samples associated with early pre main stage potassic alteration yield distinctly lower br cl ratios of 0 60 and 0 64 10 3 m butte 37cl values range from 0 8 to 2 3 with no significant difference between pre main stage and main stage samples br cl ratios for quartz veins from bingham canyon range from 0 18 to 3 68 10 3 m br cl ratios from bingham range above and below previously reported for porphyry copper deposits in contrast to butte 37cl values for bingham are lower ranging from 0 9 to 4 1 in the absence of any processes which can significantly fractionate chlorine isotopes at high temperatures we suggest that the porphyry system at bingham and to a lesser extent at butte have inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures

application of mineral equilibria modeling to constrain t and x co2 conditions during the evolution of the magdala gold deposit stawell victoria australia mineral equilibria modeling involving solid solution calculations has been combined with mineral assemblage information from the alteration zones associated with gold mineralization to determine the t and xco2 conditions for the formation of the magdala gold deposit at stawell victoria australia economic gold mineralization is primarily hosted within the stilpnomelane alteration zone of the stawell facies that is adjacent to the magdala basalt evolution of the magdala gold deposit involved at least three fluid infiltration events 1 a co2 bearing fluid during the d2 deformation event produced carbonate spots throughout the chlorite zone 2 a co2 s k bearing fluid accompanied the d3 4ab deformation and produced a muscovite zone and siderite rims on ankerite and 3 a co2 k s au bearing fluid during the d4c deformation event produced the stilpnomelane zone of the stawell facies the proximal and distal alteration zones within the magdala basalt and the main economic gold mineralization mineral equilibria modeling constrains the temperature of formation of the magdala deposit to t 345 390 c at 3kbar substantially lower than indicated by other previous classical thermobarometry methods furthermore this method has allowed the characterization of the mineralizing fluid and constrained its composition to xco2 0 08 at 3kbar the timing and composition of the mineralizing fluids are similar to that of metamorphic fluid generated from devolatilization of a greenstone pile with peak of metamorphism occurring earlier and at deeper levels in the crust

ionospheric response to the geomagnetic storm on august 21 2003 over china using gnss based tomographic technique the impacts of the august 21 2003 geomagnetic storm on the ionosphere over china have been first investigated by using the so called computerized ionospheric tomography cit technique and the observations of the crustal movement observation network of china tomographic results show that the main ionospheric effects of this geomagnetic storm over china are as follows 1 the negative storm phase effect appears in the f region and 2 the positive storm phase effect occurs above the f region meanwhile some key features in the ionospheric structure have been revealed in the ionospheric images during the storm this includes the disturbances and an elongated region of the reduced electron density at the latitude around 32 n statistical comparisons are carried out to confirm the reliability of the global navigation satellite system based cit reconstruction results using the profile obtained from ionosonde observations

principles of mobilization dissolution of metals in mafic and ultramafic rocks the role of immiscible magmatic sulphides in the generation of hydrothermal gold and volcanogenic massive sulphide deposits abstract immiscible magmatic sulphides exert a major control over both the absolute precious and base metal contents of magmas and on the availability of these metals from rocks during ore formation it is concluded that only those mafic magmas that attained s saturation at a late stage are not depleted in the chalcophile elements and are hence suitable source rocks for metals in hydrothermal ore deposits immiscible magmatic sulphides are not only strongly enriched in the ore forming metals but they are also much more reactive than silicates the ore forming metals may be liberated from the sulphides at the sea floor alteration stage and deposited in interflow chemical sediments au deposits or volcanogenic massive sulphide deposits subsequent mobilization remobilization of au from the interflow sediments may concentrate au within the interflow sediments to form economic au deposits the mobilized remobilized au may also be transported to form epigenetic style gold deposits in archaean greenstone belts and in palaeozoic slate belts

the noble gas systematics of late orogenic h2o co2 fluids mt isa australia abstract the noble gases he ne ar kr and xe are powerful geochemical tracers because they have distinctive isotopic compositions in the atmosphere crust and mantle this study illustrates how noble gases can be used to trace fluid origins in high temperature metamorphic and mineralising environments and at the same time provides new information on the composition of noble gases in deeper parts of the crust than have been sampled previously we report data for h2o and co2 fluid inclusions trapped at greenschist to amphibolite facies metamorphic conditions associated with three different styles of mineralisation and alteration in the proterozoic mt isa inlier of australia sulphide fluid inclusions are dominated by crustal 4he however co variations in fluid inclusion 20ne 22ne 21ne 22ne 40ar 36ar and 136xe 130xe indicate noble gases were derived from three or more reservoirs in most cases the fluid inclusions elemental noble gas ratios e g ne xe are close to the ranges expected in sedimentary and crystalline rocks however the elemental ratios have been modified in some of the samples providing evidence for independent pulses of co2 and interaction of co2 with high salinity aqueous fluids compositional variation is attributed to mixing of i magmatic fluids or deeply sourced metamorphic fluids characterised by basement derived noble gases with 20ne 22ne 8 4 21ne 22ne 0 4 40ar 36ar 40 000 and 136xe 130xe 8 ii basinal metamorphic fluids with a narrow range of compositions including near atmospheric values and iii noble gases derived from the meta sedimentary host rocks with 20ne 22ne 8 9 8 21ne 22ne these data provide the strongest geochemical evidence available for the involvement of fluids from two distinct geochemical reservoirs in mt isa s largest ore deposits in addition the data show how noble gases in fluid inclusions can provide information on fluid origins the composition of the crust s major lithologies fluid rock interactions and fluid fluid mixing or immiscibility processes

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

crustal scale fluid pathways and source rocks in the victorian gold province australia insights from deep seismic reflection profiles deep seismic reflection data collected across the western lachlan orogen of southeast australia have provided important insights into crustal scale fluid pathways and possible source rocks in one of the richest orogenic gold provinces in the world the profiles span three of the most productive structural zones in victoria the stawell bendigo and melbourne zones zone scale variations in the age and style of gold deposits correspond with differences in crustal structure and composition the bilateral distribution of gold production in the stawell and bendigo zones is related to the v shaped crustal scale geometry of the two zones in cross section major first order faults like the east dipping moyston fault and a set of west dipping listric faults within the bendigo zone were probably major fluid conduits in the lower to middle crust during gold mineralization first order faults in the stawell and bendigo structural zones appear to have accommodated large scale thickening down to the lower crust the faults converge in a region beneath the western bendigo zone where a thick section of mafic volcanic rocks and lesser sedimentary rocks are identified as a likely common source of gold bearing fluid that was largely generated by late ordovician to early silurian metamorphism the areas with the greatest gold endowment lie above lower crustal regions that have preserved the thickest succession of fertile mafic igneous rocks up to about 25 km thick they also correspond to a region of thin or absent precambrian lithosphere mafic rocks in the stawell zone and far western bendigo zone were probably partly consumed by cambrian west dipping subduction similar rocks in the rest of the bendigo zone lay outside the influence of cambrian subduction accretion and were deformed later probably beginning in the late ordovician early silurian benambran orogeny during crustal scale imbrication this imbrication preserved much of the mafic rocks to form the lower to middle crust first order listric faults in the bendigo zone are interpreted as major controls on the locations of goldfields even though they are largely unmineralized near the present surface the shallow dipping segments of first order listric faults were favorably oriented for reactivation at the time of gold mineralization and acted as major fluid conduits in the lower to middle crust in contrast the upper steeply dipping segments of first order listric faults were unfavorably oriented for reactivation and were poor fluid conduits the seismic data show that the transition from predominantly shallow to steeply dipping fault segments occurs in the middle to upper crust near the boundary between thick imbricated metavolcanic rocks that lie immediately below 6 to 15 km of folded metasedimentary rocks this transition may have coincided with fluid escape zones that aided the transfer of permeability away from first order faults and into the overlying fold dominated turbidites this transfer of permeability was enhanced by the growth of subvertical fold related fault and fracture meshes in the upper crustal turbidites the fault and fracture meshes consisted of bedding parallel faults limb thrusts and tension vein arrays that developed along fold hinges in the bendigo zone individual fold hinges and regional fold culminations were important controls on the distribution of fluid flow fluid flow was partly syndeformational but overlapped into the immediate postdeformational period of the benambran orogeny later reactivation of first order faults in the late silurian to early devonian and again in the late devonian led to further although less important mineralizing events as fluids exploited the preexisting fault architecture deeply penetrating north dipping listric faults in the less gold rich melbourne zone cut into inferred proterozoic basement and may have been fluid conduits during a late devonian mineralizing event

a fluid inclusion study of the fosterville mine a turbidite hosted gold field in the western lachlan fold belt victoria australia abstract gold mineralisation at fosterville occurs in association with disseminated arsenopyrite and pyrite adjacent to a complex series of quartz carbonate veins along two nnw trending fault zones quartz carbonate veins which have formed in dilational fractures within the sulphide ore zone have 18 o values between 16 0 and 17 6 and contain the following types of fluid inclusions type ia two phase liquid rich inclusions with less than 10 vol vapour and no detectable gases type ib two phase inclusions with approximately 10 vol co 2 rich vapour type ii co 2 bearing inclusions with 30 vol vapour and type iii liquid h 2 o and liquid plus vapour co 2 inclusions with variable h 2 o co 2 ratios raman microprobe analysis showed that types ib ii and iii contain co 2 with variable amounts of n 2 and ch 4 in some inclusions type 1a aqueous inclusions from stage 4 of the paragenesis have salinities ranging from 5 to 7 wt nacl equivalent whereas the co 2 bearing inclusions in the same stage have average salinities around 3 5 4 0 wt nacl equivalent the co 2 bearing inclusions exhibited two different types of homogenisation behaviour vapour rich type ii and iii inclusions either homogenised to vapour or showed near critical behaviour by gradual fading of the meniscus with homogenisation temperatures from 234 to 384 c and a mode at 270 c liquid rich co 2 bearing inclusions homogenised to the liquid phase with a bimodal distribution the majority of inclusions homogenised between 243 c and 314 c with a mode around 270 c but a secondary mode occurs around 180 c this mode corresponds fairly closely to the mode observed for the aqueous type 1a inclusions at 170 c the variable salinities coexisting liquid and vapour rich inclusions and the overlap of the homogenisation temperatures suggest that phase separation has occurred during vein formation and the resulting depth of mineralisation is estimated to be between 2 6 and 5 7 km gold precipitation resulted from the partitioning of h 2 s into the vapour phase during fluid unmixing which was enhanced both by the decreasing pressure as fluid flowed from the faults and veins into the host rocks and by the addition of n 2 and ch 4 comparisons with available fluid inclusion data for the western lachlan fold belt indicates that the fosterville gold field formed at lower temperatures and at a higher crustal level than the quartz reef style of gold deposits in the bendigo ballarat zone the fluids at fosterville also contain greater amounts of n 2 and ch 4 suggesting that the mineralising fluids penetrated further into the host rocks and reacted either directly with carbonaceous matter or with reduced fluids contained within the host rocks

spreading and potential instability of teide volcano tenerife canary islands 1 we analyze the role of low strength materials in the potential structural instability related to volcano spreading at the active teide stratovolcano tenerife canary islands to study the low strength materials we took advantage of a network of large tunnels within the volcano excavated for water supply which allows the in situ inspection and reconstruction of both volcano and substratum structure we identified two factors which are potentially important to teide s instability 1 a dipping low strength substratum breccia layer and 2 a hydrothermally altered weak core inside the volcano despite we do not find clear structural evidence for volcano substratum spreading both teide topographic shape and the summit faulting are features similar to those accepted as examples of volcano flank spreading over a weak core the detected asymmetric deformation of the edifice makes the north flank of teide a strong candidate for a potential failure

stratigraphy structure and geochronology of the las canadas caldera tenerife canary islands after a long period of subaerial fissure fed extrusions of basaltic magmas 12 to 3 ma volcanic activity was then concentrated in the central part of tenerife phonolitic magma chambers formed and a central volcanic complex was constructed the las canadas edifice the formation of a large depression the las canadas caldera truncated the top of the edifice the active twin strato cones teide pico viejo are sited in this depression the history of the las canadas caldera and edifice are established from stratigraphy geochronology k ar dates and volcanological studies two different groups are recognized separated by a major unconformity the lower group is dated at 2 to 3 ma and includes the products of several volcanic centres which together represent several cycles the upper group ranges from 1 56 to 0 17 ma and includes three different formations representing three long term 100 to 300 ka volcanic cycles the periods of dormancy between each formation were of 120 to 250 ka duration the las canadas caldera is a multicyclic caldera which formed over the period 1 18 0 17 ma each cycle of activity represented by a formation culminated in caldera collapse which affected different sectors of the las canadas edifice geological observation and geochronology support an origin by collapse into a magma chamber the minimum volume of pyroclastic ejecta is substantially greater than the present caldera depression volume 45 km3 but approaches the inferred volume of the original caldera depression 140 km3 after the formation of the caldera sector collapses could also occur at the northern flank of the volcano causing the disappearance of the northern side of the caldera wall

the spectrum of persistent volcanic flank instability a review and proposed framework based on kīlauea piton de la fournaise and etna abstract persistent motion of the south flank of k lauea volcano hawai i has been known for several decades but has only recently been identified at other large basaltic volcanoes namely piton de la fournaise la reunion and etna sicily thanks to the advent of space geodetic techniques nevertheless understanding of long term flank instability is based largely on the example of k lauea despite the large differences in the manifestations and mechanisms of the process when viewed through a comparative lens for example the rate of flank motion at k lauea is several times that of etna and piton de la fournaise and is accommodated on a slip plane several km deeper than is probably present at the other two volcanoes gravitational spreading also appears to be the dominant driving force at k lauea given the long term steady motion of the volcano s south flank regardless of eruptive intrusive activity whereas magmatic activity plays a larger role in flank deformation at etna and piton de la fournaise k lauea and etna however are both characterized by heavily faulted flanks while piton de la fournaise shows little evidence for flank faulting a helpful means of understanding the spectrum of persistent flank motion at large basaltic edifices may be through a framework defined on one hand by magmatic activity which encompasses both magma supply and edifice size and on the other hand by the structural setting of the volcano especially the characteristics of the subvolcanic basement or subhorizontal intravolcanic weak zones a volcano s size and magmatic activity will dictate the extent to which gravitational and magmatic forces can drive motion of an unstable flank and possibly the level of faulting of that flank while the volcano s structural setting governs whether or not a plane of weakness exists beneath or within the edifice and can facilitate flank slip considering persistent flank instability using this conceptual model is an alternative to using a single volcano as a type example especially given that the example is usually k lauea which defines an extreme end of the spectrum and can provide a basis for understanding why flank motion may or may not exist on other large basaltic volcanoes worldwide

convergence and intraplate deformation in the lachlan fold belt of southeastern australia abstract the lachlan fold belt of southeastern australia is dominated by a widespread oceanic association including cambrian submarine mafic volcanics and an overlying widespread ordovician quartz rich turbidite and black shale succession with scattered mafic to andesitic volcanic centres these rocks are overlain by or in fault contact with deep marine to continental silurian to early carboniferous successions with mafic to silicic volcanics and abundant plutonic rocks major deformation achieved by thrusting and folding affected the fold belt during the silurian to middle devonian and the early carboniferous shortening estimates vary throughout the belt but the widespread ordovician quartz turbidite succession usually has at least 60 shortening which implies an original width of the fold belt of about 1700 km strike slip faulting was important on a local to regional scale but large scale strike slip displacements appear unlikely the large values of shortening are consistent with development of the belt in a convergent margin setting at least for the silurian to carboniferous the nature of the lower crust of the lachlan fold belt has always presented a problem of interpretation but we favour a late proterozoic quasi continental lower crustal layer that has deformed independently of the upper crust by either homogeneous flattening or crustal duplexing during silurian carboniferous convergence and provided a source for silurian devonian granites

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