sulfur isotopic studies of the dunka road cu ni deposit duluth complex minnesota the dunka road deposit is one of a series of cu ni occurrences located within troctolitic rocks of the southern portion of the duluth complex minnesota sulfide minerals principally pyrrhotite chalcopyrite cubanite and minor pentlandite occur interstitially with silicate minerals and average about 2 volume percent in ore grade horizons areas of sulfide concentrations in excess of 1 to 2 percent occur erratically throughout the troctolitic sequence but are in general concentrated near the basal contact with rocks of the metasedimentary virginia formation the delta 34 s values of sulfides in the troctolites range from 0 2 to 15 8 per mil with an average value near 7 5 per mil pyrrhotite in the underlying virginia formation hornfels and pyrite from unmetamorphosed virginia formation are characterized by a similar range in delta 34 s values the high positive delta 34 s values and similarity to values found in the virginia formation strongly suggest that most of the sulfur in the dunka road deposit was derived from the breakdown of pyrite in the virginia formation the sulfur isotopic compositions of minerals in the troctolites show no consistent lateral or vertical trends and are in general characterized by a high degree of variability such fluctuations in delta 34 s values indicate that sulfur isotopic homogenization was not attained throughout the troctolitic sequence several mechanisms may have contributed to the variations in delta 34 s values found within the troctolites including mixing of sedimentary and igneous sulfur assimilation of sedimentary sulfur characterized by variable delta 34 s values fractionation caused by fluctuations in oxidation states during sulfur volatilization and assimilation and periodic introduction of isotopically distinct magma batches in light of the erratic sulfide mineral and delta 34 s distributions the predominant mechanism is thought to be the introduction of both isotopically and spatially variable country rock sulfur into crystallizing troctolitic magma

sinking cities in indonesia alos palsar detects rapid subsidence due to groundwater and gas extraction abstract we use interferometric synthetic aperture radar insar time series analysis of alos l band sar data to resolve land subsidence in western indonesia with high spatial and temporal resolution the data reveal significant subsidence in nine areas including six major cities at rates up to 22 cm year land subsidence is detected near lhokseumawe in medan jakarta bandung blanakan pekalongan bungbulang semarang and in the sidoarjo regency the fastest subsidence occurs in highly populated coastal areas particularly vulnerable to flooding we correlate the observed subsidence with surface geology and land use despite the fact that subsidence is taking place in compressible deposits there is no clear correlation between subsidence and surface geology in urban areas we find a correlation between rapid patchy subsidence and industrial land use and elsewhere with agricultural land use this suggests that the subsidence is primarily caused by ground water extraction for industrial and agricultural use respectively we also observe subsidence associated with exploitation of gas fields near lhokseumawe and in the sidoarjo regency a continuation of these high rates of subsidence is likely to put much of the densely populated coastal areas below relative sea level within a few decades

proterozoic depletion of the lithosphere recorded in mantle xenoliths from inner mongolia mantle xenoliths entrained in alkali basalt provide direct samples from a cross section of the lithosphere in most cases the chemistry and isotope systematics of these objects have suggested a complex history of chemical change by processes such as metasomatism and partial melting see for example ref 1 here however we present evidence from a suite of xenoliths from alkali basalts in the chinese province of inner mongolia suggesting that the lithosphere in this region has remained stable and closed to chemical modification since experiencing partial melting in the proterozoic clinopyroxene separates from these xenoliths yield an approximate isochron in the 143nd 144nd versus 147sm 144nd diagram suggesting an episode of depletion 1 6 gyr ago although other explanations for this correlation such as mixing cannot be ruled out definitively further evidence for the long term undisturbed nature of the lithosphere in this region comes from neodymium model ages of the clinopyroxenes in particular one highly depleted sample with very high 147sm 144nd provides a model age of 1 6 gyr consistent with the isochron result

evidence of the present relative land stability of venice italy from land sea and space observations 1 the city of venice is very vulnerable to loss in surface elevation as a result of subsidence and eustacy because of its small elevation above sea level the alarm of the scientific community related to this persistent problem is increasing because of the forecasts of sea level rise caused by global warming in order to evaluate the present relative subsidence of venice a study has been performed by combining high precision leveling satellite radar interferometry sri and tide gauge measurements the analysis of the most recent data points out with an unprecedented detail the present ground stability of the city

variations in os isotope ratios of pyrrhotite as a result of water rock and magma rock interaction constraints from virginia formation duluth complex contact zones abstract os isotope ratios in pyrrhotite bearing pelitic rocks of the 1 85 ga virginia formation are variable with perturbations linked to the emplacement of the 1 1 ga duluth complex pyrrhotite in footwall rocks of the contact aureole show evidence for a mixing event at 1 1 ga involving a low 187 os 188 os fluid however because rocks with perturbed pyrrhotite os isotope ratios occur 1 km or more from the duluth complex the fluid is unlikely to have been of magmatic origin fluid inclusions in layer parallel quartz veins provide evidence of the involvement of a boiling fluid at temperatures between 300 and 400 c analyses of fluid inclusions via la icp ms show that the fluids contain up to 1 7 wt na 1 1 wt k 4330 ppm fe 2275 ppm zn and 415 ppm mg the veins also contain pyrite or pyrrhotite plus minor amounts of chalcopyrite bornite pentlandite and sphalerite the re os isotopic ratios of pyrite from the veins indicate that they crystallized from low 187 os 188 os fluids 18 o values of vein quartz range from 7 7 to 9 5 consistent with an origin involving fluid with a relatively low 18 o value between 2 and 5 meteoric water with such a low 18 o value could have interacted with the igneous rocks of the complex and would have acquired os with a low 187 os 188 os ratio strongly serpentinized olivine rich rocks of the complex are commonly characterized by such low 18 o values and we propose that the fluid involved in serpentinization was also responsible for the perturbation of the os isotopic system recorded by pyrrhotite in the virginia formation two important observations are that only pyrrhotite bearing assemblages in the contact aureole show isotopic perturbation and that intervals showing os exchange are spatially restricted and not uniformly distributed os exchange and mixing has occurred only where temperatures were sufficient to convert pyrite to pyrrhotite and where time integrated water rock ratios in the aureole were high enough to provide a supply of os troctolitic and gabbroic rocks of the partridge river intrusion duluth complex are characterized by os isotope ratios that are indicative of variable degrees of crustal contamination os values of 0 543 xenoliths of carbonaceous and sulfidic pelitic rocks of the virginia formation found in the igneous rocks provide evidence that os was released by organic matter and pyrite in the sedimentary rocks and assimilated by mantle derived magma however residual pyrrhotite produced as a result of pyrite breakdown in the xenoliths is characterized by 187 os 188 os ratios that are much lower than anticipated and similar to those of pyrrhotite in the contact aureole the os exchange and addition shown by pyrrhotite in the xenoliths highlight an unusual cycle of re os liberation during devolatilization kerogen maturation and pyrite to pyrrhotite conversion processes that contribute to magma contamination followed by os uptake by pyrrhotite during back reaction involving magma and or fluid characterized by a relatively low 187 os 188 os ratio the extreme os uptake recorded by pyrrhotite in the xenoliths as well as the lesser degree of uptake recorded by pyrrhotite in the contact aureole is in line with the high os diffusivity in pyrrhotite experimentally determined by brenan et al 2000 our data confirm that os isotope ratios in pyrrhotite bearing rocks may be readily perturbed for this reason caution should be exercised in the interpretation of os isotope ratios in rocks where pyrrhotite may be the primary host of os

isotopic evolution of mauna loa volcano abstract in an effort to understand the temporal helium isotopic variations in mauna loa volcano we have measured helium strontium and lead isotopes in a suite of mauna loa lavas that span most of the subaerial eruptive history of the volcano the lavas range in age from historical flows to ninole basalt which are thought to be several hundred thousand years old most of the samples younger than 30 ka in age kau basalt are radiocarbon dated flows while the samples older than 30 ka are stratigraphically controlled kahuku and ninole basalt the data reveal a striking change in the geochemistry of the lavas approximately 10 ka before present the lavas older than 10 ka are characterized by high 3 he 4 he 16 20 times atmospheric higher 206 pb 204 pb 18 2 and lower 87 sr 86 sr 0 70365 ratios than the younger kau samples having he pb and sr ratios of approximately 8 5 atmospheric 18 1 and 0 70390 respectively the historical lavas are distinct in having intermediate sr and pb isotopic compositions with 3 he 4 he ratios similar to the other young kau basalt 8 5 atmospheric the isotopic variations are on a shorter time scale 100 to 10 000 years than has previously been observed for hawaiian volcanoes and demonstrate the importance of geochronology and stratigraphy to geochemical studies the data show consistency between all three isotope systems which suggests that the variations are not related to magma chamber degassing processes and that helium is not decoupled from the other isotopes however the complex temporal evolution suggests that three distinct mantle sources are required to explain the isotopic data most of the mauna loa isotopic variations could be explained by mixing between a plume type source similar to loihi and an asthenospheric source with helium isotopic composition close to morb and elevated sr isotopic values an asthenospheric source or variation within the plume source is considered more likely than lithospheric sources due to the elevated 87 sr 86 sr ratios in the recent kau basalts however the distinct isotopic characteristics of the historical lavas are inferred to be related to lithospheric involvement in the latest stages of shield building volcanism

separating natural and anthropogenic vertical movements in fast subsiding areas the po plain n italy case the geological and the anthropogenic components of vertical movement act on different time scales millions to thousands years and hundreds to tens of years respectively this peculiarity has been used in order to separate the factors controlling sea level changes in the po plain area the component due to long term geological processes is calculated from stratigraphic data commercial wells and seismic lines adding to this long term component the contribution of pleistocene deglaciation obtained from analytical models an estimate of the total natural component of vertical velocities is obtained the validity of these values is confirmed by comparison with velocities obtained from archaeological data and detailed palynological and paleontological analyses the anthropogenic components can be inferred by comparison between the total natural vertical velocities we calculate and vertical velocities obtained from other data sets two applications are proposed using tide gauge records and geodetic data respectively

transient deformation in california from two decades of gps displacements implications for a three dimensional kinematic reference frame our understanding of plate boundary deformation has been enhanced by transient signals observed against the backdrop of time independent secular motions we make use of a new analysis of displacement time series from about 1 000 continuous global positioning system gps stations in california from 1999 to 2018 to distinguish tectonic and nontectonic transients from secular motion a primary objective is to define a high resolution three dimensional reference frame datum for california that can be rapidly maintained with geodetic data to accommodate both secular and time dependent motions to this end we compare the displacements to those predicted by a horizontal secular fault slip model for the region and construct displacement and strain rate fields over the past 19 years california has experienced 19 geodetically detectable earthquakes and widespread postseismic deformation we observe postseismic strain rate variations as large as 1 000 nstrain year with moment releases equivalent up to an mw6 8 earthquake we find significant secular differences up to 10 mm year with the fault slip model from the mendocino triple junction to the southern cascadia subduction zone the northern basin and range and the santa barbara channel secular vertical uplift is observed across the transverse ranges coastal ranges sierra nevada as well as large scale postseismic uplift after the 1999 mw7 1 hector mine and 2010 mw7 2 el mayor cucapah earthquakes we also identify areas of vertical land motions due to anthropogenic natural and magmatic processes finally we demonstrate the utility of the kinematic datum by improving the accuracy of high spatial resolution 12 day repeat cycle sentinel 1 interferometric synthetic aperture radar displacement and velocity maps

mineral deposits of the mesoproterozoic midcontinent rift system in the lake superior region a space and time classification abstract the mesoproterozoic midcontinent rift system mrs of north america hosts a diverse suite of magmatic and hydrothermal mineral deposits in the lake superior region where rift rocks are exposed at or near the surface historically hydrothermal deposits such as michigan s native copper deposits and the white pine sediment hosted stratiform copper deposit were major mrs metal producers on going exploration for and potential development of copper nickel sulfide deposits hosted by the duluth complex of minnesota and the opening of the eagle nickel mine in michigan indicate an expanding interest in mrs magmatic deposits mrs hydrothermal and magmatic mineral deposits many of which are significant past present and likely future providers of critical minerals here are placed into a space and time metallogenic framework to construct this framework regional mrs mineral deposits extracted from the u s geological survey mineral resources data system mrds and the ontario ministry of energy northern development and mines mineral deposit inventory mdi were supplemented by other known and recently recognized mineral deposits described in the literature all mineral deposits were classified by deposit type host rock age and type and estimated timing of mineralization deposits were then put into a tectonic evolutionary framework stages for the mrs which shows that deposits formed within discrete spatial and temporal stages of rift evolution each stage of rift evolution is characterized by specific mineral deposit types that are largely confined both by their physical location in rift rocks and type and timing of mineralization examples include mrs nickel rich conduit type magmatic sulfide deposits which are restricted to an early magmatic stage mrs history when magma compositions were characterized by ni rich picrites and high mg basalts in contrast contact type magmatic sulfide deposits with cu ni were derived from more evolved al rich tholeiitic magmas that dominated a later time of voluminous magmatic activity hydrothermal sediment hosted stratiform chalcocite mineralization along the margins of western lake superior in michigan is economic only where fluid flow through red beds was concentrated by structures along the margins of a post volcanic mrs sedimentary basin widespread native cu and native ag mineralization occurred about 40 million years after formation of host basalt lava flows and interflow sedimentary rocks these descriptions of the diverse mineral deposits in the lake superior region cataloged within the space of the local and regional geology and over the more than 60 million year mineralizing history of the mrs are indicative of the complex and at times overlapping magmatic and hydrothermal mineral systems that operated within this major large igneous province

on the mechanisms for low sulfide high platinum group element and high sulfide low platinum group element mineralization in the eastern gabbro coldwell complex canada evidence from textural associations s se values and platinum group element concentrations of base metal sulfides

lessons from venus for understanding mantle plumes on earth abstract mantle plumes are important in the magmatic and tectonic history for both earth and venus the expression of plumes is distinctive on venus and complementary to that on earth therefore a cross comparison is useful for better understanding plume magmatism on both planets in contrast to the earth venus has no observed record of plate tectonics a low degree of surface erosion and an apparently short duration for the formation of the present planetary surface the absence of plate tectonics indicates that all magmatism is intraplate and is generated beneath a stagnant lithospheric lid a low degree of surface erosion preserves the surface structures and short wavelength topography the short duration of preserved magmatic activity suggests a global resurfacing event magmatic elements include a individual volcanoes with diameters ranging up to 1000 km which represent hotspots b annular structures termed coronae with diameters averaging 300 km but ranging up to 2600 km and which appear to lack terrestrial i e earth analogues c radiating graben fissure systems extending up to 2000 km in radius some of which are purely uplift related while others mark the plumbing system dyke swarms of volcanic systems d lava flow fields of scale comparable to terrestrial flood basalts large igneous provinces lips and e regions of small shield volcanoes representing shallow source melting there are several hierarchies of magmatic events on venus ordered in terms of increasing scale and significance 1 isolated coronae volcanoes flow fields and radiating graben systems 2a individual and small clusters of volcanoes and coronae associated with topographic swells geoid highs and triple junction rifting these are most clearly indicative of terrestrial type plumes originating from the deep mantle 2b coronae distributed along rifts chasmata these are the clearest examples of melt generation associated with rifting 3 regional concentration of activity in the beta atla themis bat region this is the closest example of a plume cluster event sometimes termed a superplume event and 4 global volcanic resurfacing of the volcanic plains no terrestrial analogue is confirmed although the global burst of terrestrial plume activity in the neoarchean is a possible analogue

comment on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar by y bock s wdowinski a ferretti f novali and a fumagalli

evolutionary aspects of lithosphere discontinuity structure in the western u s 1 we have produced common conversion point ccp stacked ps and sp receiver function image volumes of the moho and lithosphere asthenosphere boundary lab beneath the western united states using transportable array data the large image volumes and the diversity of tectonic environments they encompass allow us to investigate evolution of these structural discontinuities the moho is a nearly continuous topographic surface whereas the lab is not and the seismic images show a more complex expression the first order change in lab depth in the western u s occurs along the cordilleran hingeline the former laurasian passive margin along the southwestern precambrian north american terranes the lab is about 50 deeper to the east of the hingeline than to the west with most of the increase in lab thickness being in the mantle lithosphere we infer that the moho and the lab are late mesozoic or cenozoic everywhere west of the hingeline modified during farallon subduction and its aftermath between the hingeline and the rocky mountain front the lab and to a lesser extent the moho have been partially reset during the cenozoic by processes that continue today seismicity and recent volcanism in the interior of the western u s are concentrated along gradients in crustal and or lithospheric thickness for example the hingeline and the eastern edge of the coastal volcanic magmatic terranes to us this suggests that lateral gradients in integrated lithospheric strength focus deformation similarly areas conjectured to be the sites of convective downwellings and associated volcanism are located along gradients in regional lithosphere thickness

geochemistry of tholeiites from lanai hawaii lanai is the third smallest of the fifteen principal subaerial shield volcanoes of the hawaiian hotspot this volcano apparently became extinct during the shield building stage of volcanism as shown by the absence of both alkalic cap and post erosional lavas major and trace element analyses of 22 new samples collected primarily from 3 stratigraphic sections show that lanai tholeiites span a large range in composition some lanai lavas are unique geochemically among hawaiian tholeiites in having the lowest abundances of incompatible trace elements of any hawaiian lavas and well developed positive eu anomalies the geochemical characteristics of these low abundance lanai tholeiites are not the result of alteration differences in mantle source modal mineralogy the presence of residual accessory mantle phases or fractional crystallization of such phases assimilation of depleted morb wall rock or accumulation resorption of phenocrysts or xenocrysts incompatible trace element ratios e g nb la nb th la th la hf ce pb in lanai tholeiites span considerable ranges and form coherent trends with each other and with absolute abundances of these elements large variations in la sm la yb and absolute ree abundances at constant mgo suggest that lanai tholeiites formed by variable amounts of partial melting however large ranges in incompatible element ratios cannot be explained solely by variations in partial melting of a geochemically homogeneous source but must reflect geochemical heterogeneities in the lanai source partial melting modeling indicates that the mixed lanai source is probably lree enriched i e la yb cn 1 one component in the lanai source exemplified by the low abundance tholeiites has markedly lower ree hfse th hfse alkali hfse and ce pb ratios than other lanai or hawaiian tholeiites and may indicate the presence of recycled residual subduction zone materials in the hawaiian plume source the positive eu anomalies that characterize the low abundance lanai tholeiites are not the result of plagioclase accumulation or assimilation but are a feature of this source component progressive temporal geochemical variations in lanai tholeiites from 2 stratigraphic sections indicate that the source composition of these lavas probably evolved over time this change could have resulted from a progressive decrease in the extent of partial melting of the lanai source the compositional variability of lanai tholeiites suggests that geochemical heterogeneities in their source are larger than the scale of partial melting lanai tholeiites could not have formed by smaller degrees of partial melting of plume material than did the larger volume hawaiian shields therefore volume differences between hawaiian shields must be controlled primarily by differences in the volume of supplied plume material rather than by differences in the degree of partial melting the premature cessation of eruptive activity at lanai may be attributed to relatively large degrees of partial melting of a small plume

mantle and slab contributions in arc magmas destructive plate margins are major sites of terrestrial magmatism that have long had a key role in models for the generation of continental crust and the development of chemical heterogeneities in the upper mantle in these models it is important to evaluate the nature and size of contributions from preexisting crust in the generation of magmas above subduction zones and to constrain the size of the fluxes of different elements from the subducted crust and the overlying mantle wedge in arc magmas kay 1 980 hawkesworth ellam 1 989 hawkesworth et al 1 99 1 a mcculloch gamble 1 99 1 the more mobile components of the subducted oceanic crust are the products of element fractionation processes in the upper continental crust the ocean basins and hydrothermal systems on the ocean floor they therefore have distinctive isotope and even trace element ratios that in principle should be readily distinguished from those in peridotite in the mantle wedge prior to subduction in practice however element ratios are almost certainly fractionated during shallow level dehydration of sub ducted material and at greater depths where material from the slab appears to contribute in the generation of arc magmas moreover the isotope signal of slab derived material may be heavily diluted by exchange with

inflation rate of the colli albani volcanic complex retrieved by the permanent scatterers sar interferometry technique 1 we analyzed 99 ers sar images of the colli albani volcano using the permanent scatterers technique we retrieved the average surface displacement velocities for over 100 000 scatterers for the period 1993 2000 showing that present deformation is concentrated in the area of most recent volcanic activity with rates up to 2 6 mm yr in the satellite line of sight we inverted the observed deformation using several analytical solutions for volcanic sources in an elastic half space the best fit is obtained with two mogi sources aligned in a n s direction at 5 and 7 km depth beneath the western flank of the volcano

apennines subduction related subsidence of venice italy 1 the foreland regional monocline related to the northern apennines subduction can be followed from the po basin to the friuli region italy at least 240 km north eastward in seismic reflection profiles of the po basin and of the northern adriatic sea the dip of the regional monocline gradually decreases from about 22 to close to 0 pleistocene sediments onlap and pinchout to the northeast venice is located on a segment of the active monocline dipping about 1 8 to the southwest in sediments around the venice area the 1 43 ma limit is in the 960 1500 m depth range indicating a long term subsidence rate of about 0 7 1 0 mm yr therefore a significant part of the natural component of the town subsidence is related to the north eastward retreat of the adriatic subduction the subduction related downflexure affects the whole of the po plain basin and part of the southern alps where it opposes to the general uplift related to orogenesis

the mesoproterozoic midcontinent rift system lake superior region usa abstract exposures in the lake superior region and associated geophysical evidence show that a 2000 km long rift system developed within the north american craton 1109 1087 ma the age span of most of the volcanic rocks this system is characterized by immense volumes of mafic igneous rocks mostly subaerial plateau basalts generated in two major pulses largely by a hot mantle plume a new ocean basin was nearly formed before rifting ceased perhaps due to the remote effect of the grenville continental collision to the east broad sagging subsidence combined with a system of axial half grabens separated along the length of the rift by accommodation zones provided conditions for the accumulation of as much as 20 km of volcanic rocks and as much as 10 km of post rift clastic sediments both along the rift axis and in basins flanking a central post volcanic horst pre rift mature quartzose sandstones imply little or no uplift prior to the onset of rift volcanism early post rift red bed sediments consist almost entirely of intrabasinally derived volcanic sediment deposited in alluvial fan to fluvial settings the exception is one gray to black carbon bearing lacustrine unit this early sedimentation phase was followed by broad crustal sagging and deposition of progressively more mature red bed fluvial sediments with an extra basinal provenance

a laser ablation inductively coupled plasma mass spectrometry study of the distribution of chalcophile elements among sulfide phases in sedimentary and magmatic rocks of the duluth complex minnesota usa abstract nickel copper sulfide deposits occur in the basal unit of the partridge river intrusion duluth complex minnesota usa many lines of evidence suggest that these sulfides are formed after assimilation of the proterozoic s rich black shales known as the bedded pyrrhotite unit in addition to s black shales are enriched in te as bi sb and sn tabs and the basaltic magma of the intrusion is contaminated by the partial melt of the black shales the tabs are chalcophile and together with the platinum group elements ni and cu partitioned into the magmatic sulfide liquid that segregated from the duluth magma the tabs are important for the formation of platinum group minerals pgm thus their role during crystallization of the base metal sulfide minerals could affect the distribution of the pge however the concentrations of tabs in magmatic ni cu pge deposits and their distribution among base metal sulfide minerals are poorly documented in order to investigate whether the base metal sulfide minerals host tabs in magmatic ni cu pge deposits a petrographic and laser ablation inductively coupled plasma mass spectrometry la icp ms study has been carried out on base metal sulfide and silicate phases of the partridge river intrusion duluth complex petrographic observations showed that the proportions of the base metal sulfide minerals vary with rock type the sulfide assemblage of the least metamorphosed bedded pyrrhotite unit from outside the contact metamorphic aureole consists of pyrite with minor pyrrhotite plus chalcopyrite 95 with small amount of chalcopyrite our la icp ms study shows that sulfides of the bedded pyrrhotite unit are rich in tabs consistent with these s rich black shales being the source of tabs that contaminated the mafic magma most of the tabs are associated with sulfides and platinum group minerals in the rocks of the bedded pyrrhotite unit from the contact aureole the bedded pyrrhotite unit xenoliths and the mafic rocks of the duluth complex in addition to these phases the laser maps show that silicate phases i e orthopyroxene and plagioclase contain sn and pb respectively in contrast in the least metamorphosed samples of the bedded pyrrhotite unit from outside the contact aureole although the pyrite contains some tabs mass balance calculations indicates that most the tabs are contained in other phases in these rocks galena hosts significant amounts of te bi sb sn and ag and few very small grains of sb rich phases were also observed the host phases for as were not established but possibly organic compounds may have contributed

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

on the use of quasi static deformation to understand reservoir fluid flow deformation above a producing reservoir provides a valuable source of information concerning fluid flow and flow properties quasi static deformation occurs when the displacements are so slow that we may neglect inertial terms in the equations of motion we present a method for inferring reservoir volume change and flow properties such as permeability from observations of quasi static deformation such displacements may represent surface deformation such as tilt leveling interferometric synthetic aperture radar insar or bathymetry observations or subsurface deformation as inferred from time lapse seismic surveys in our approach the equation for fluid flow in a deforming reservoir provides a mapping from estimated fractional volume changes to reservoir permeability variations if the reservoir behaves poroelastically over the interval of interest all the steps in this approach are linear thus the inference of reservoir permeability from deformation data becomes a linear inverse problem in an application to the wilmington oil field in california we find that observed surface displacements obtained by leveling and insar are indeed compatible with measured reservoir volume fluxes we find that the permeability variations in certain layers coincide with fault block boundaries suggesting that in some cases faults are controlling fluid flow at depth

quantitative evidence that compaction of holocene sediments drives the present land subsidence of the po delta italy 1 deltas are highly dynamic coastal systems that over the last few decades have generally experienced a substantial area loss caused by trapping of river sediments in upland drainage basins as well as land subsidence due to natural and anthropogenic causes a major example is the po delta in the mediterranean in northeastern italy this area has experienced as much as 3 m of land subsidence from the 1930s to the 1970s primarily because of the extraction of gas bearing waters however present subsidence rates are largely unknown and the ground settlement is supposedly controlled by natural long term deep processes we have combined radar interferometric point target analysis ipta with previous geomorphological investigations on aerial satellite images and seismic surveys and geochronological data from core samples and geomechanical in situ tests to assess the current sinking of the delta and to understand the processes controlling the vertical movement the high density of the measurable point targets more than 15 000 allows characterization of the spatial variation in the vertical land motions vlm ranging from 1 to 15 mm yr we find that subsidence rates are significantly correlated with the age of highly compressible holocene deposits that compose the shallowest 30 40 m of the sedimentary sequence a typical log type consolidation equation applicable at the scale of the entire delta has been obtained we conclude that the consolidation of late holocene sediments is the major cause of the present land subsidence in the po river delta this finding has significant impact on the understanding of many other modern deltas that were formed in the lower holocene epoch

selenium and sulfur concentrations in country rocks from the duluth complex minnesota usa implications for formation of the cu ni pge sulfides various studies suggest that the formation of a magmatic ni cu platinum group element pge sulfide deposit requires addition of s from the country rocks into the magma many sulfide deposits have s se ratios higher than primary magmas which is attributed to the preferential addition of s from the country rocks however this has not been clearly demonstrated because most studies do not determine se in the country rocks partly because although se concentration in igneous rocks can be assessed by most routine analytical techniques their detection limits are too low for measuring with precision the level of se in sedimentary rocks we have determined se abundances using thiol cotton fiber tcf combined with instrumental neutron activation analysis inaa s and delta super 34 s on the magmatic sulfides of the duluth complex and on the host rock sediments of the virginia formation our data show that the pelitic and metapelitic rocks of the virginia formation are characterized by low s se ratios approximately 3 000 close to the mantle values whereas the s rich layer known as the bedded pyrrhotite unit has high s se ratios approximately 20 000 consequently most of the virginia formation sediments and xenoliths are unsuitable as a source of s because they have s se ratios and delta super 34 s values lower than those of the mineralized rocks 10 000 only the bedded pyrrhotite unit which is present at the contact with the intrusion and as partly digested xenoliths within the intrusion has s se ratios and delta super 34 s values higher than those of the magmatic sulfides and could thus be the source of the s furthermore the presence of sulfides in the norites around the xenoliths suggests that the s was released from the xenolith during melting of the xenolith detailed sampling from the xenoliths into the norite shows that the s se ratio and delta super 34 s decrease with distance from the xenolith our results favor a mechanism of crustal s contamination by in situ assimilation of bedded pyrrhotite unit xenoliths

the role of black shales as a source of sulfur and semimetals in magmatic nickel copper deposits example from the partridge river intrusion duluth complex minnesota usa the basal unit of the duluth complex minnesota usa contains ni cu sulfide deposits the s in these is thought to be derived from a sulfide rich black shale unit known as the bedded pyrrhotite unit a stratigraphic unit within the virginia formation host rocks however the mechanism of s transfer has not been clearly established in order to understand how this transfer occurs we have undertaken petrography and whole rock geochemistry of the rocks from the contact aureole and the basal unit in the contact aureole the bedded pyrrhotite unit consists of a very fine grained graphitic shales with thin beds of sulfides consisting of pyrrhotite with minor chalcopyrite 1 the basal unit contains numerous bedded pyrrhotite unit xenoliths surrounded by norites the bedded pyrrhotite unit xenoliths are partially melted and the sulfide beds are disrupted leucosomes are present and these contain blebs of sulfides consisting of pyrrhotite pentlandite cubanite and chalcopyrite in the mafic rocks surrounding the xenoliths small patches of sulfide bearing leucosome are found in addition to being rich in s the bedded pyrrhotite unit is rich in as 38 ppm sb 4 1 ppm and bi 0 6 ppm and te 0 4 ppm and has high 34s values the 34s as s bi s and sb s decrease with distance from the xenoliths similarly the ni s cu s se s and platinum group elements s ratios are higher in the mafic rocks and increase with distance from the xenoliths our model proposes that droplets of sulfide melt derived from the bedded pyrrhotite unit xenoliths were entrained in the anatectic silicate melt of the xenoliths and transferred to the mafic magma the sulfide droplets equilibrated with the mafic magma those close to the xenoliths did not have the opportunity to react with a large quantity of magma and hence their composition is similar to the sulfides of the bedded pyrrhotite unit i e rich in semimetals and poor in ni cu and pge farther away from the xenoliths the sulfide droplets could have reacted with more magma and the composition of these sulfides approach that of sulfides derived mainly from mafic magma

topography correlated atmospheric delay correction in radar interferometry using wavelet transforms 1 atmospheric delay is one of the major sources of error in repeat pass interferometry we propose a new approach for correcting the topography correlated components of this artifact to this aim we use multiresolution wavelet analysis to identify the components of the unwrapped interferogram that correlate with topography by using a forward wavelet transform we break down the digital elevation model and the unwrapped interferogram into their building blocks based on their frequency properties we apply a cross correlation analysis to identify correlated coefficients that represent the effect of the atmospheric delay thus the correction to the unwrapped interferogram is obtained by down weighting the correlated coefficients during inverse wavelet transform we test this approach on real and synthetic data sets that are generated over the san francisco bay area we find that even in the presence of tectonic signals this method is able to reduce the correlated component of the atmospheric delay by up to 75 and improves the signal in areas of high relief the remaining part is most likely due to 3d heterogeneities of the atmosphere and can be reduced by integrating temporal information or using complementary observations or models of atmospheric delay

sulfur and oxygen isotope studies of melt country rock interaction babbitt cu ni deposit duluth complex minnesota the babbitt cu ni deposit formerly known as minnamax occurs within troctolitic and gabbroic rocks of the precambrian duluth complex both massive and disseminated mineralizations are found in the deposit pyrrhotite cubanite chalcopyrite and minor pentlandite mineralization occurs near the basal contact with pelitic metasedimentary rocks of the virginia formation or higher in the igneous sequence associated with abundant country rock xenoliths cloud zones sulfur and oxygen isotope studies have been carried out to evaluate the importance of melt country rock interaction in localizing sulfide mineralization the delta 34 s values of pyrrhotite plus pyrite from the virginia formation located outside the contact aureole range from 5 6 to 13 7 per mil pyrrhotite from footwall virginia formation hornfels or inclusions in the basal zone exhibits delta 34 s values ranging from 1 5 to 6 2 per mil whereas delta 34 s values of pyrrhotite from xenoliths in cloud zones range from 2 6 to 21 4 per mil isotopic values of basal zone cu ni sulfides range from 6 0 to 13 0 per mil with a mode at 8 to 9 per mil two features highlight basal zone delta 34 s values first delta 34 s values of sulfide mineralization are higher than those of pyrrhotite in immediately adjacent virginia formation hornfels second higher grade ore areas 1 cu show 34 s enrichment with delta 34 s values in the range of 9 to 13 per mil sulfides in cloud zones show a wide range in delta 34 s values from 0 7 to 19 7 per mil sulfur isotope data suggest that most of the sulfur found in the deposit has been derived from sedimentary country rocks however an in situ process of sulfur derivation is not indicated sulfur in basal mineralized zones must have been derived at depth within an auxiliary magma chamber or during magma ascent and emplacement isotopic homogenization was not achieved during the sulfide forming process as evidenced by the spatial variability of delta 34 s values oxygen isotope values of both mildly metamorphosed virginia formation and footwall hornfels range from 8 2 to 14 0 per mil inclusions of virginia formation show pronounced isotopic effects due to interaction with melt xenolith margins may have values as low as 7 to 8 per mil and are depleted in 18 o with respect to xenolith interiors the delta 18 o values of igneous rocks from the babbitt deposit range from 3 9 to 12 2 per mil zones of 18 o depletion are rare and suggest that exchange with a low 18 o fluid phase was spatially restricted anomalous delta 18 o values in excess of 7 to 7 5 per mil are common throughout the deposit but are limited to within 3 m of virginia formation xenoliths a model of diffusion controlled 18 exchange between igneous material and xenoliths best describes the delta 18 o distribution devolatilization and desilicification of the xenoliths occurred early in their history when physical mixing in the host magma was possible addition of high 18 o material from these processes into a large volume of melt affected delta 18 o distributions only slightly continued exchange of oxygen after major cation transfer produced the observed delta 18 o profiles in the case of basal zone cu ni mineralization at babbitt isotopic evidence indicates that sulfide saturation was not caused by in situ addition of sulfur silica or oxygen sulfide saturation is thought to have been achieved at depth triggered by assimilation of large quantities of sulfide liberated through devolatilization reactions occurring in country rocks

madagascar basalts tracking oceanic and continental sources extensive upper cretaceous volcanism in southern madagascar was fed in part by mantle sources resembling those expressed today in the indian ocean at marion and prince edward islands and on the central southwest indian ridge in addition very low end t to 17 4 high 87sr 86sr t to 0 72126 tholeiites in southwestern madagascar were variably but highly contaminated by ancient continental material broadly like that affecting the bushe and poladpur formations of the later deccan traps in india alkalic dikes in southwestern madagascar have a rough analogue in the mahabaleshwar formation of the deccan in that they document the influence of a low 206pb 204pb negative end relatively low 87sr 86sr reservoir a very similar reservoir is manifested at present in mid ocean ridge basalts on the central southwest indian ridge near 40 e the original location of this end member appears likely to have been in the madagascan lithospheric mantle a portion of which may have been removed in the middle cretaceous by the action of the marion hotspot or the rifting of indo madagascar an origin within the hotspot itself also may be possible however recent products of the hotspot appear to lack completely the necessary low 206pb 204pb low end signatures

on the fate of mantle plumes at density interfaces abstract the motion of plumes through compositionally layered systems is investigated by laboratory experiments in order to understand the ascent modes of deep mantle plumes experimental plumes entrain the ambient heavier fluid and the average density of the plume head p t increases with time the degree of entrainment depends on the viscosity ratio of the matrix fluid matrix to the buoyant fluid buoyant and the mass flux two types of plume penetration through the density interface are possible the first which can be characterized as a pass through mode ptm exhibits relatively little entrainment here the whole plume head passes directly through the interface because p t is smaller than the density of the upper layer u in contrast in the second type of interaction named the rebirth mode rbm a large entrainment effect takes place the plume is now greatly disturbed as it passes through the interface between the two fluid layers and entrained material remains at the density interface since p t u in addition a new diapir emerges from the plume conduit and rises through the upper layer the difference between these two types of interaction is reflected in the spatial and the temporal characteristics of geochemical data obtained from mantle plume products such as ontong java plateau ojp

recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 coastal regions are increasingly affected by larger storms and rising sea level predicted by global warming models aggravating the situation in the city of venice where tidal induced seasonal flooding coupled with natural and anthropogenic subsidence have been perennial problems in light of accelerated efforts to protect venice from the rise in sea level we assess land subsidence in the venice lagoon over the last decade through a combined analysis of gps position time series from 2001 55 to 2011 00 for four stations installed by the magistrato alle acque di venezia and thousands of observations of insar permanent scatterers using radarsat 1 images from 2003 3 to 2007 85 we determine that the northern lagoon subsides at a rate of 2 3 mm yr whereas the southern lagoon subsides at 3 4 mm yr the city of venice continues to subside at a rate of 1 2 mm yr in contrast to geodetic studies in the last decade of the 20th century suggesting that subsidence has been stabilized the gps results indicate a general eastward tilt in subsidence and that the natural subsidence rate related to the retreat of the adriatic plate subducting beneath the apennines is at least 0 4 0 6 mm yr our combined gps and insar analysis demonstrates high spatial resolution in the vertical direction with a precision of 0 1 0 2 mm yr with respect to a global reference frame continued efforts to secure the city of venice from flooding must also take into account the significant local and regional subsidence rates as well as the expected rise in sea level

tahiti geochemical evolution of a french polynesian volcano the island of tahiti the largest in french polynesia comprises two major volcanoes aligned nw se parallel with the general trend of the society islands hotspot track rocks from this volcanic system are basalts transitional to tholeiites alkali basalts basanites picrites and evolved lavas through k ar radiometric dating we have established the age of volcanic activity the oldest lavas 1 7 ma crop out in deeply eroded valleys in the center of the nw volcano tahiti nui while the main exposed shield phase erupted between 1 3 and 0 6 ma and a late stage valley filling phase occurred between 0 7 and 0 3 ma the sw volcano tahiti iti was active between 0 9 and 0 3 ma there is a clear change in the composition of lavas through time the earliest lavas are moderately high sio2 evolved basalts mg number mg mg mg fe2 42 49 probably derived from parental liquids of composition transitional between those of tholeiites and alkali basalts the main shield lavas are predominantly more primitive olivine and clinopyroxene phyric alkali basalts mg 60 64 while the later valley filling lavas are basanitic mg 64 68 and commonly contain peridotitic xenoliths olivine orthopyroxene clinopyroxene spinel isotopic compositions also change systematically with time to more depleted signatures rare earth element patterns and incompatible element ratios however show no systematic variation with time we focused on a particularly well exposed sequence of shield building lavas in the punaruu valley on the western side of tahiti nui combined k ar ages and magnetostratigraphic boundaries allow high resolution age assignments to this 0 7 km thick flow section we identified an early period of intense volcanic activity from 1 3 to 0 9 ma followed by a period of more intermittent activity from 0 9 to 0 6 ma flow accumulation rates dropped by a factor of 4 at about 0 9 ma this change in rate of magma supply corresponds to a shift in activity to tahiti iti we calculated the composition of the parent magma for the shield building stage of volcanism assuming that it was in equilibrium with fo89 olivine and that the most primitive aphyric lavas were derived from this parent by the crystallization of olivine alone the majority of the shield lavas represent 25 to 50 crystallization of this parent magma but the most evolved lavas represent about 70 crystallization from over 50 analyzed flow units we recognize a quasi periodic evolution of lava compositions within the early robust period of volcanic activity which we interpret as regular recharge of the magma chamber approximately every 25 10 kyr volcanic evolution on tahiti is similar to the classic hawaiian pattern as the shield building stage waned the lavas became more silica undersaturated and isotopic ratios of the lavas became more morb like we propose that the society plume is radially zoned due to entrainment of a sheath of viscously coupled depleted mantle surrounding a central core of deeper mantle material all parts of the rising plume melt but the thermal and compositional radial gradient ensures that greater proportions of melting occur over the plume center than its margins the changing composition of tahitian magmas results from lithospheric motion over this zoned plume magmas erupted during the main shield building stage are derived mainly from the hot incompatible element enriched central zone of the plume late stage magmas are derived from the cooler incompatible element depleted viscously coupled sheath a correlation between pb ce and isotope ratios suggests that the society plume contains deeply recycled continental material

assessing short and long time displacements in the venice coastland by synthetic aperture radar interferometric point target analysis 1 the venice lagoon in italy is a unique environment vulnerable to loss in surface elevation relative to the mean sea level we present detailed synthetic aperture radar sar interferometric analyses on persistent point targets for the historical center of venice the tourist area of sottomarina and the zennare farmland close to the southern lagoon edge the selected areas are characterized by different degrees of development and our analyses show the remarkable capability of sar interferometric point target analysis ipta to map land displacement rates in densely urbanized zones and to detect movement information on isolated structures with a mm year accuracy a detailed analysis of the time series from 1992 to 2000 provided by ipta shows that the vertical component of the measured displacements are the superposition of a short timescale generally seasonal movement on the order of 1 cm that is likely related to the fluctuation of environmental variables temperature piezometric head in the aquifer system underlying the lagoon sea lagoon water level and a long term ground deformation associated with building construction the geomorphology of the area and the human development of natural resources if venice is confirmed to be generally stable significant long term subsidence on the order of 4 mm year is detected at the sottomarina coastland the highest displacement rates of up to 8 10 mm year are recorded in the farmland bounding the lagoon margin where the movements are found to be highly site specific

petrogenesis of pelitic xenoliths at the babbitt cuni deposit duluth complex minnesota u s a abstract the babbitt deposit consists of disseminated cu fe ni sulfides found within mafic rocks of the duluth complex generally near contacts with underlying metasedimentary rock types host rocks for the deposit include troctolites olivine gabbros gabbronorites norites and occasionally country rock hornfels xenoliths of country rocks are abundant in the deposit and suggest a relationship between sulfide mineralization and country rock contamination country rocks in the babbitt area include those of the middle precambrian biwabik iron formation and both calcareous and non calcareous pelites of the virginia formation xenoliths contain the assemblage cordierite plagioclase biotite orthopyroxene and are thought to have been derived from virginia formation protoliths comparison of protoliths and xenoliths using composition volume element ratio and mass balance techniques suggests that xenoliths have been strongly depleted in volatiles alkalis and si footwall rocks show only a depletion in volatiles neither fluid phase transport nor diffusion through an intergranular fluid can account for the mass of material transferred extensive partial melting of xenoliths with residual enrichment of feo mgo and al2o3 is the most viable transfer process the lack of sio2 concentration gradients around xenoliths and anomalous igneous rock compositions suggest that desilicification occurred at a time when physical mixing of extracted partial melt and host magma was possible and prior to final emplacement sulfide saturation may have been initiated due to si assimilation with an auxiliary magma chamber however the composition of ores in the babbitt deposit is consistent with saturation being achieved by addition of sediment derived volatile sulfur independent of major element assimilation

highly siderophile and strongly chalcophile elements in magmatic ore deposits an ore deposit by definition must be economically viable that is to say it must contain sufficient material at high enough grade to make it possible to mine and process it at a profit bates and jackson 1987 this requires the elements to be collected and concentrated by some phase and for them to be deposited close to the surface of the earth at the oxygen fugacities found in the crust native fe is not normally stable and thus the highly siderophile elements defined as ru rh pd re os ir pt and au cannot behave as siderophile elements except in rare cases such as on disko island klock et al 1986 where the magma is sufficiently reduced for native fe to be present however if mafic magmas become saturated in a base metal sulfide liquid the highly siderophile elements behave as highly chalcophile elements table 1 thus these elements are generally found in association with base metal sulfide minerals which crystallized from a magmatic sulfide liquid namely pyrrhotite pentlandite chalcopyrite cubanite pyrite an exception to this is au although au is strongly chalcophile and is produced as a by product from many platinum group element pge deposits table 2 most primary au deposits consist of native au groves et al 1998 these will not be discussed in this chapter there are many pge deposits i e accumulations of pge minerals and base metal sulfides containing pge bates and jackson 1987 around the world but most of these do not constitute pge ore deposits because they are either too small or their grade is too low or other political or infrastructure factors prevent the economic exploitation of the deposit bates and jackson 1987 for the purpose of this work we have defined pge ore deposits as those which have significant production 2 of the annual world

geodetic control on recent tectonic movements in the central mediterranean area abstract during the neogene and quaternary the western mediterranean geodynamics was apparently dominated by the nearly eastward migration of the apenninic arc and the associated opening spreading of the back arc basin tyrrhenian sea however during the last 5 my the collision of the arc with the apulian platform led to a dramatic change in the tectonic setting of the area as geological processes require a long period of time to register the displacements of the different blocks it is indispensable to take into account the present day motion given by space geodesy data analysis in order to better constrain the geological models geodetic motions were derived from global positioning system gps satellite laser ranging slr and very long baseline interferometry vlbi observations collected from different networks all the geodetic solutions have been computed and combined at the centre of space geodesy cgs at matera italy the geodetic results show a nne motion of the adriatic plate with a small component of counter clockwise rotation in good agreement with the geological and geophysical observations in the southern tyrrhenian area the lengthening of the matera cagliari baseline should imply that convergence cannot be considered as the driving mechanism for the apenninic subduction process the estimated motion of noto is in quite good agreement with the estimated motion of the african plate

exploiting uavsar for a comprehensive analysis of subsidence in the sacramento delta abstract the sacramento san joaquin delta like other heavily engineered deltas throughout the world has undergone substantial subsidence since the late 1800s when the natural estuary was leveed to form islands today islands within the delta have subsided to the point where most lie below mean sea level long term sustainability of the delta requires reversal of subsidence but spatially comprehensive maps of subsidence have not been available to inform and monitor remediation reported here is the first spatially dense map of recent subsidence rates across the delta based on synthetic aperture radar interferometry and constrained by gnss observations the analysis uses a temporally dense and spatially overlapping set of data acquired by the uninhabited aerial vehicle sar uavsar sensor in 2009 2015 on average the delta is subsiding by 9 2 4 4 mm yr with high variability even at the sub island scale including peak subsidence of 160 4 4 mm yr occurring just inland of the levee of the westernmost island and average subsidence of 11 mm yr along the planned path of water conveyance tunnels through the delta the results are compared to local sea level rise slr measured at a tidal gauge in san francisco bay to show that subsidence is currently the dominant contributor to local relative sea level rise rslr by nearly a factor of five based on recently measured and modeled acceleration of slr subsidence in the delta is likely to dominate rslr until the middle of the 21th century

helium isotope ratios in easter microplate basalts abstract 3 he 4 he ratios in easter microplate basalt glasses show clear evidence of the effects of a mantle plume the east rift of the microplate between 26 and 28 s identified by la sm sr and pb isotopes and ridge crest elevation as the region of maximum plume influence has 3 he 4 he ratios spanning the entire range from 7 5 to 11 7 r a the easter microplate is the only section of the entire east pacific rise that is associated with a known hotspot track mantle plume and has elevated 3 he 4 he ratios although most of the west rift basalts contain morb helium 8 0 8 7 r a the basalt closest to the east rift has an elevated 3 he 4 he ratio 11 3 r a consistent with a significant plume component the diversity in isotopic signatures also indicates that homogenization of isotopic anomalies does not occur even in this region of super fast spreading the overall 3 he 4 he 206 pb 204 pb and 3 he 4 he 87 sr 86 sr trends have positive correlations although the high 3 he 4 he 87 sr 86 sr and 206 pb 204 pb component is not a single value but rather a broad band the apparent decoupling between the he and sr isotope distribution is modeled in the context of a plume source migrating ridge sink during channeling of the plume toward the ridge helium is preferentially lost from the center of the channeled plume resulting in lower he pb and he sr concentration ratios in the high 3 he 4 he component mixing trajectories in he sr isotopic space between a lile depleted asthenosphere and a variably degassed plume component provide a reasonably good fit to the data and may explain the isotope systematics of plume ridge interactions in the context of modern theories of plume dynamics

evidence of regional subsidence and associated interior wetland loss induced by hydrocarbon production gulf coast region usa analysis of remote images elevation surveys stratigraphic cross sections and hydrocarbon production data demonstrates that extensive areas of wetland loss in the northern gulf coast region of the united states were associated with large volume fluid production from mature petroleum fields interior wetland losses at many sites in coastal louisiana and texas are attributed largely to accelerated land subsidence and fault reactivation induced by decreased reservoir pressures as a result of rapid or prolonged extraction of gas oil and associated brines evidence that moderately deep hydrocarbon production has induced land surface subsidence and reactivated faults that intersect the surface include 1 close temporal and spatial correlation of fluid production with surficial changes including rapid subsidence of wetland sediments near producing fields 2 measurable offsets of shallow strata across the zones of wetland loss 3 large reductions in subsurface pressures where subsidence rates are high 4 coincidence of orientation and direction of displacement between surface fault traces and faults that bound the reservoirs and 5 accelerated subsidence rates near producing fields compared to subsidence rates in surrounding areas or compared to geological rates of subsidence based on historical trends subsidence rates in the gulf coast region near producing fields most likely will decrease in the future because most petroleum fields are nearly depleted alternatively continued extraction of conventional energy resources as well as potential production of alternative energy resources geopressured geothermal fluids in the gulf coast region could increase subsidence and land losses and also contribute to inundation of areas of higher elevation

geochemical tracers of mantle processes the mantle can be sampled directly only very rarely geochemists have thus come to rely heavily on mantle derived magmas to study the composition and evolution of the mantle only those compositional features that are unaffected by magmatic processes are useful as tracers of mantle processes these include radiogenic isotope ratios such as those of he sr hf and os stable isotope ratios and ratios of highly incompatible elements or elements of similar incompatibility such as ba nb or pb ce the term incompatible denotes a preference of the element for a melt over mantle minerals highly incompatible elements will partition entirely into the melt under most circumstances so that the ratio of two such elements in a basalt will be virtually identical to that ratio in its source this is also true to a lesser degree of ratios such as la sm and zr nb as zr and sm are not highly incompatible elements

persistent scatterer interferometry analysis of ground deformation in the po plain piacenza reggio emilia sector northern italy seismo tectonic implications

time dependent model of creep on the hayward fault from joint inversion of 18 years of insar and surface creep data 1 spatial and temporal variations of aseismic fault creep influence the size and timing of large earthquakes along partially coupled faults to solve for a time dependent model of creep on the hayward fault we invert 18 years of surface deformation data 1992 2010 obtained by interferometric processing of 52 and 50 sar images acquired by the ers1 2 and envisat satellites respectively and surface creep data obtained at 19 alinement and 4 creepmeter stations for multi temporal analysis of the sar data we developed a method for identifying stable pixels using wavelet multi resolution analysis we also implement a variety of wavelet based filters for reducing the effects of environmental artifacts using a reweighted least squares approach we inverted the interferometric data to generate a time series of surface deformation over the san francisco bay area with a precision of better than a few millimeters to jointly invert the insar displacement time series and the surface creep data for a time dependent model of fault creep we use a robust inversion approach combined with a kalman filter the time dependent model constrains a zone of high slip deficit that may represent the locked rupture asperity of past and future m 7 earthquakes we identify several additional temporal variations in creep rate along the hayward fault the most important one being a zone of accelerating slip just northwest of the major locked zone we estimate that a slip rate deficit equivalent to mw 6 3 6 8 has accumulated on the fault since the last event in 1868

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

isotopic evidence for the origin of the manihiki and ontong java oceanic plateaus abstract pb nd and sr isotopic results for lavas of the cretaceous ontong java and manihiki oceanic plateaus fall well within the modern day oceanic island or hotspot field the data provide no evidence of old continental basements but indicate a major involvement of kerguelen type or em i like mantle in the sources of both plateaus which appear to have probably been formed at least in part by hotspots however the presently active hotspots that pacific plate reconstructions suggest might have been possible plateau sources lack kerguelen type isotopic compositions either these hotspots did not participate in the formation of the two plateaus or if they did kerguelen type material must have been volumetrically much more important early in their existence two hypotheses for the origins of these plateaus which involve hotspot sources are consistent with the sparse available geochemical geochronological and geophysical data the first holds that the plateaus formed cataclysmically in association with surfacing plume heads the second posits a relatively steady but robust hotspot at or near a ridge crest and requires a much longer period of formation a near ridge origin appears to be indicated by evidence that most of the pacific plateaus were built largely on relatively young ocean crust however we suggest that a near ridge origin is also compatible with the plume head concept in that plume heads appear very likely to become associated with spreading axes through their influence on rift propagation which should be substantially greater than for ordinary hotspots in either case the lack of hotspot tracks seamount chains attached to the two plateaus would be a consequence of ridge migration or rift propagation in a near ridge setting

aseismic deformation across the hilina fault system hawaii revealed by wavelet analysis of insar and gps time series abstract the hilina fault system hfs is located on the south flank of kilauea volcano and is thought to represent the surface expression of an unstable edifice sector that is active during seismic events such as the 1975 kalapana earthquake despite its potential for hazardous landsliding and associated tsunamis no fault activity has yet been detected by means of modern geodetic methods since the 1975 earthquake we present evidence from individual sar interferograms as well as cluster analysis and wavelet analysis of gps and insar time series which suggest an inferred differential motion at hfs to investigate the effect of atmospheric delay on the observed differential motion we implement a statistical approach using wavelet transforms we jointly analyze insar and continuous gps deformation data from 2003 to 2010 to estimate the likelihood that the subtle time dependent deformation signal about the hfs scarps is not associated with the atmospheric delay this integrated analysis reveals localized deformation components in the insar deformation time series that are superimposed on the coherent motion of kilauea s south flank the statistical test suggests that at 95 confidence level the identified differential deformation at hfs is not due to atmospheric artifacts since no significant shallow seismicity is observed over the study period we suggest that this deformation occurred aseismically

space geodesy subsidence and flooding in new orleans a subsidence map of the city offers insight into the failure of the levees during hurricane katrina

land subsidence in houston texas measured by radar interferometry and constrained by extensometers 1 we present results from a radar interferometry study over the houston galveston texas gulf coast region from the nearly 60 potential interferograms considered an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis the subsequent interferogram time series spanning 1996 1998 is constrained by coincident extensometer data with root mean square error less than 2 5 mm the interferogram time series confirms that historic subsidence in east houston has stopped consistent with current groundwater use patterns broad scale subsidence bowls are observed in west and northwest houston where maximum subsidence rates are in excess of 2 and 4 cm yr 1 respectively linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults including the long point fault in northwest houston are observed near the seabrook extensometer a hereto unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr 1 is revealed this study demonstrates that when used in conjunction with a set of traditional geodetic measurements radar interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments

dynamics of slow moving landslides from permanent scatterer analysis high resolution interferometric synthetic aperture radar insar permanent scatterer data allow us to resolve the rates and variations in the rates of slow moving landslides satellite to ground distances range changes on landslides increase at rates of 5 to 7 millimeters per year indicating average downslope sliding velocities from 27 to 38 millimeters per year time series analysis shows that displacement occurs mainly during the high precipitation season during the 1997 1998 el nino event rates of range change increased to as much as 11 millimeters per year the observed nonlinear relationship of creep and precipitation rates suggests that increased pore fluid pressures within the shallow subsurface may initiate and accelerate these features changes in the slope of a hill resulting from increases in the pore pressure and lithostatic stress gradients may then lead to landslides

petrochemical studies of the dunka road cu ni deposit duluth complex minnesota troctolitic sequence divided into three major units oxygen isotope values confirm the chemical studies and indicate that major element assimilation is restricted to within approximately 10 m of country rock inclusions pyrrhotite crystallization followed by separation of a cu rich sulfide melt blending and partial crystallization of chemically similar magma and enrichment of cu in the final residual liquid modified journal abstract

a new project to monitor land subsidence in the northern venice coastland italy the paper deals with the implementation of a levelling and global positioning system gps network to control land subsidence in the coastal area north of the venice lagoon about 480 km of levelling lines with 527 benchmarks 45 of which suited for differential gps measurements were established in 2004 a complete survey of the net was carried out in 2004 soon after its establishment the 2004 records have been compared with previous scattered data obtained by the use of levelling surveys dgps and sar interferometry the results show a trend in land settlement that increases from the lagoon margin to the north and jeopardize the venice coastland groundwater withdrawals for domestic agricultural and health spas uses peat oxidation of reclaimed marshlands for farming natural consolidation of the holocene deposits and tectonics of the pre quaternary basement are the causes of land subsidence in the study area since most of the area lies below the mean sea level and on account of the expected sea level rise due to global change a detailed monitoring of land displacements in the near future will be of paramount importance to plan necessary works for coastland protection

vertical land motion and relative sea level changes along the coastline of brest france from combined space borne geodetic methods abstract in spite of the recent advances and the current perspectives of satellite radar altimetry to reach the coastline and monitor coastal sea level changes this space borne technology remains geocentric by essence in contrast the quantity that matters for coastal management and society is relative sea level that is the sea level relative to the land as measured by conventional tide gauges however two important issues are associated with the use of tide gauges first supplemental information is required to separate vertical land motion from ocean climate signals in tide gauge records and hence to understand the causes of future coastal sea level changes and their relative importance this can be provided by space borne geodetic techniques for instance installing a permanent global positioning system gps antenna at the tide gauge second vertical land motion can show local spatial patterns which limits the spatial validity of the point wise information at the gps station using interferometry synthetic aperture radar insar and high precision gps data the above mentioned limitations were addressed in the case study of brest france our findings show that over the past decades brest and its surroundings are overall stable in agreement with the geological setting except for the embankment areas of the commercial and military harbours the gps calibrated insar results were then further combined with geocentric satellite radar altimetry data to obtain relative sea level trends along the brest coastline with an unprecedented high spatial resolution of 200 m our approach is applicable beyond the case study of brest especially in coastal areas where tide gauge data are not available provided satellite data are

high nonlinear urban ground motion in manila philippines from 1993 to 2010 observed by dinsar implications for sea level measurement abstract in coastal low lying urban areas vertical ground motions can significantly exacerbate the hazards related to sea level rise however their spatial extent their temporal evolution and even sometimes their existence are often poorly known this study aims to monitor variable urban ground motion uplift and subsidence from 1993 to 2010 in the metropolitan area of manila philippines because high subsidence rates have been reported in this city in previous studies conventional differential sar interferometry dinsar was applied with an adapted stacking procedure to the archive of ers and envisat satellite images to produce surface deformation velocity maps for different periods the results showed that the city is locally affected by vertical ground motions on the order of 15 cm yr moreover the spatio temporal evolution of the ground motion phenomena is highly nonlinear these results are in good agreement with previous studies focused on groundwater use in manila and in the marikina fault valley suggesting a plausible interpretation of the processes causing surface motion incidentally the ground motions are affecting the locations of several geodetic instruments including a tide gauge with sea level records starting in 1902 two permanent gps global positioning system stations and a doris doppler orbitography and radiopositioning integrated by satellite station a major implication of those large and locally variable ground motions is that they impede the use of the nearby gps and doris data to correct the tide gauge records and to derive robust sea level trends associated with climate change

decoding the origins of vertical land motions observed today at coasts in recent decades geodetic techniques have allowed detecting vertical land motions and sea level changes of a few millimetres per year based on measurements taken at the coast tide gauges on board of satellite platforms satellite altimetry or both global navigation satellite system here contemporary vertical land motions are analysed from january 1993 to july 2013 at 849 globally distributed coastal sites the vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic green s functions special attention is paid to the effects of glacial isostatic adjustment induced by past and present day ice melting various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally in well instrumented regions predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres residual vertical land motions show a strong local variability especially in the vicinity of plate boundaries due to the earthquake cycle significant residual signals are also observed at scales of a few hundred kilometres over nine well instrumented regions forming observation windows on unmodelled geophysical processes this study highlights the potential of our multitechnique database to detect geodynamical processes driven by anthropogenic influence surface mass changes surface loading and glacial isostatic adjustment and tectonic activity including the earthquake cycle sediment and volcanic loading as well as regional tectonic constraints future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models

land subsidence in houston correlated with flooding from hurricane harvey abstract hurricane harvey caused unprecedented flooding and socioeconomic devastation in eastern texas with high winds elevated storm tide and record rainfall the flooded area is mapped using the radar backscattering difference between sentinel 1a b satellite acquisitions spanning the event which provides a snapshot of standing water at the time of image acquisition we find vast areas outside of designated flood hazard zones are overwhelmed furthermore we map pre cyclone land subsidence using multitemporal interferometric processing of large sar datasets acquired by advanced land observation satellite alos and sentinel 1a b satellites we find that subsidence of up to 49 mm yr and 34 mm yr during the alos jul 2007 jan 2011 and sentinel 1a b dec 2015 to aug 2017 acquisition periods affect various parts of houston galveston area we conclude that 85 of the flooded area subsided at a rate 5 mm yr we suggest that subsidence affected flood severity by modifying base flood elevations and topographic gradients supported by the chi square test of independence this work highlights the importance of incorporating insar measurements of land subsidence in flood resilience strategies

chemical and mineralogical heterogeneity in the basal zone of the partridge river intrusion implications for the origin of cu ni sulfide mineralization in the duluth complex midcontinent rift system copper nickel sulfide mineralization in the partridge river intrusion of the 1 1 ga duluth complex is restricted primarily to a 100 m thick zone near the base of the intrusion which is heterogeneous at meter scales in terms of both sulfide contents and rock types which include dunite melatroctolite troctolite leucotroctolite gabbro olivine gabbro gabbronorite and rare norite olivine rich troctolites and melatroctolites appear to have required mineral accumulation on a substrate whereas augite troctolite and gabbros are thought to have formed via in situ crystallization of magmas ranging in composition from high al olivine tholeiite to high ti tholeiite 18o values of orthopyroxene poor rocks in the partridge river intrusion range from 5 2 to 6 7 18o values of 6 7 are consistent with less than 20 contamination by high 18o metasedimentary country rock either via devolatilization or local partial melting rocks with greater than 15 orthopyroxene gabbronorites and norites are characterized by 18o values in excess of 6 9 and required the assimilation of larger amounts of siliceous country rocks sulfur isotopic values in leucotroctolitic rocks that contain less than 400 ppm s and that overlie the basal zone range between 1 5 and 2 values that are consistent with those of mantle derived sulfur in contrast 34s values in the basal zone range from 1 4 to 10 5 where the 34s enriched samples require an input of sulfur from metasedimentary country rocks 34s values of the rocks in the basal zone correlate with variations in olivine fo content but not with s abundance the wide range in 34s values of rocks in the basal zone strongly suggests that magmas interacted with layers in the sedimentary country rocks that were themselves characterized by variable sulfide contents and 34s values the s isotopic data suggest that the heterogeneity observed in the basal zone results from the emplacement of relatively thin sheets of compositionally distinct magma all rock types present in the basal zone can be produced as a result of variable degrees of fractionation of a parental high al olivine tholeiite followed by varying degrees of contamination of derivative liquids by country rocks the s contamination process was essential for the development of cu ni mineralization and was restricted to the earliest stages in the development of the duluth complex at a time when volatile species such as s and h2o and low t partial melts of country rocks were available to magmas

geochemical variations in lavas from kahoolawe volcano hawaii evidence for open system evolution of plume derived magmas the kahoolawe shield volcano produced precaldera and caldera filling tholeiites and mildly alkalic post caldera lavas that petrographically and compositionally resemble such lavas from other hawaiian shield volcanoes however kahoolawe tholeiites display wide ranges in incompatible trace element ratios e g nb th 9 24 th ta 0 6 1 3 87sr 86sr 0 70379 0 70440 143nd 144nd 0 51273 0 51298 and 206pb 204pb 17 92 18 37 the isotopic variation exceeds that at any other hawaiian shield volcano and spans about half the range for all hawaiian tholeiites quasi cyclic temporal evolution of kahoolawe tholeiites is consistent with combined fractional crystallization and periodic recharge by primitive magmas ratios of highly incompatible trace elements and sr nd and pb isotopic ratios from coherent sub trends that reflect recurrent interactions between variably evolved magmas and two other mantle components whose compositions are constrained by intersections between these trends the most mgo rich kahoolawe tholeiites are partial melts of a high nb th 23 5 ascending plume possibly comprising ancient subducted oceanic lithosphere slightly evolved tholeiites experienced combined crystal fractionation and assimilation afc of material derived from a distinct reservoir nb th 9 of asthenospheric derivation the most evolved tholeiites display compositional shifts toward a third component having mid ocean ridge basalt like isotopic ratios but enriched oib like trace element ratios representing part of the lithospheric mantle or melts thereof periodic recurrence of all three magma variants suggests that eruptions may have tapped coeval reservoirs distributed over a large depth range kahoolawe provides new evidence concerning the nature of the hawaiian plume the distribution of compositional heterogeneities in the suboeanic mantle and the processes by which hawaiian tholeiites form and evolve

mapping ground deformation over houston galveston texas using multi temporal insar abstract houston galveston hg region in texas has been subsiding due to the combined effects of groundwater withdrawal hydrocarbon extraction salt dome movement and faulting this human and partially nature induced ground deformation has gradually threatened the stability of urban infrastructure and caused the loss of wetland habitat along the gulf of mexico interferometric synthetic aperture radar insar techniques can measure ground motions in high spatial resolution over large coverage the purpose of this study is to map the spatial and temporal variations in surface deformation around the hg region using a multi temporal insar mti technique and to assess the role of fluid withdrawal groundwater withdrawal and hydrocarbon extraction salt tectonics and fault activity in land surface deformation mti derived land surface deformation measurements are then compared to gps and extensometer observations geologic and hydrologic data and information about hydrocarbon extraction to address the causes of the observed deformation the mti measurements based on ers 1 2 datasets have mapped regional subsidence up to 53 mm yr in the northwestern hg as well as a slight uplift at 20 mm yr in the southeastern hg from 1993 to 2000 insar measurements obtained from envisat and alos data reveal subsidence rate of up to 30 mm yr over the northwestern hg between 2004 and 2011 our results indicate that the pattern of ground deformation was nearly concentric around locations of intense groundwater withdrawal and the spatial extent of the subsiding area has been shrinking and migrating toward the northeast after 2000 we have resolved localized ground subsidence cones over hydrocarbon exploration fields which were likely caused by reservoir compaction we have differentiated ground surface deformation over salt domes which was due to ongoing differential movement of individual salt spines we have identified 5 40 mm yr differential subsidence across a number of faults in the region these faults functioned as water barriers disrupting the integrity of ground water flow and aggravating localized surface displacements

the influence of country rock assimilation and silicate to sulfide ratios r factor on the genesis of the dunka road cu ni platinum group element deposit duluth complex minnesota the dunka road deposit is one of several cu ni platinum group element pge sulfide occurrences found along the northwestern margin of the duluth complex where the host troctolitic rocks are in contact with metasedimentary rocks of the animikie group magma contamination through assimilation of sulfidic argillaceous country rocks is generally recognized as having played a key role in the genesis of the mineralization three main types of disseminated sulfide mineralization have been identified within the dunka road deposit i norite hosted sulfides ii troctolite hosted sulfides and iii pge rich sulfide horizons the norite hosted sulfides are found either adjacent to country rock xenoliths or near the basal contact the troctolite hosted sulfides form the bulk of the deposit and occur throughout the lower 250 m of the intrusion the pge rich sulfide horizons are typically localized directly beneath ultramafic layers the composition of the different types of sulfide occurrences is modelled using cuipd ratios it is shown that each type results from the interplay of two main parameters namely the degree of magma contamination and the silicate magma to sulfide melt ratio r factor the norite hosted sulfides formed at low r factors and high degrees of contamination as expressed by their pge depleted nature low seis ratios and elevated content in pyrrhotite and arsenide minerals the troctolite hosted sulfides formed at moderate r factors and small degrees of contamination as shown by their moderate pge content and mantle like seis ratios finally the pge rich sulfide horizons are modelled using elevated r factors from an uncontaminated parental magma which is substantiated by their elevated noble metal content and seis ratios and low pyrrhotite to precious metal sulfide ratio le gite de dunka road est un parmi plusieurs gites de sulfures de cu ni elements du groupe du platine egp trouves le long de la bordure nord ouest du complexe de duluth ou les roches hotes troctolitiques sont en contact avec les roches metasedimentaires du groupe d animikie il est generalement reconnu que la contamination du magma par l assimilation de roches argileuses sulfurees encaissantes a joue un role capital dans la genese de la mineralisation trois types principaux de mineralisation de sulfures dissemines ont ete identifies dans le gite de dunka road i sulfures dans la norite hote ii sulfures dans la troctolite hote et iii horizons de sulfures enrichis en egp les sulfures dans la norite hote apparaissent soit dans les zones adjacentes aux xenolites encaissants ou pres du contact basal les sulfures dans la troctolite hote forment le plus gros du gisement et ils apparaissent dans les 250m inferieurs de l intrusion la localisation typique des horizons de sulfures enrichis en egp se trouve directement sous les couches ultramafiques les rapports cu pd ont ete utilises pour elaborer un modele de la composition des differents types de mineralisation de sulfures il est demontre que chaque type resulte de l interaction de deux parametres dominants a savoir le degre de contamination du magma et le rapport du magma silicate au liquide sulfure facteur r les sulfures dans la norite hote ont ete formes sous des conditions de faibles facteurs r et de fortes contaminations comme en temoignent la teneur appauvrie en egp les faibles rapports se s et les concentrations elevees de la pyrrhotite et des mineraux arsenieux les sulfures dans la troctolite hote ont ete formes sous des conditions de facteurs r moderes et de faibles contaminations comme le revelent leur teneur modere en egp et les rapports se s analogues a ceux du manteau finalement les horizons de sulfures enrichis en egp sont modelises en utilisant des facteurs r eleves et un magma parental non contamine ce qui est appuye par leur forte teneur en elements nobles et les rapports se s eleves et par le rapport faible de la pyrrhotite sur les sulfures de metaux precieux

applicability of sentinel 1 terrain observation by progressive scans multitemporal interferometry for monitoring slow ground motions in the san francisco bay area 2017 american geophysical union all rights reserved data from the sentinel 1 satellite have already proven useful for investigating seismic and volcanic events since its launch in april 2014 the requirement of ultrahigh coregistration accuracy and the current relatively short time of sentinel 1 acquisitions make its application challenging for studying slow deformation processes such as fault creep and land subsidence here we analyze a set of 14 sar images over the san francisco bay area spanning 1 year from early 2015 to 2016 we show that implementing an existing enhanced spectral diversity algorithm or using precise orbits together with a reference digital elevation model both yield the required coregistration accuracy for making use of the phase measurements in time series analysis of ground deformation following a thorough validation test we update our estimates of hayward fault creep rate and confirm uplift due to recharge of the santa clara valley aquifer system during the final summer of 4 year drought

southern california permanent gps geodetic array spatial filtering of daily positions for estimating coseismic and postseismic displacements induced by the 1992 landers earthquake the june 28 1992 m w 7 3 landers california earthquake was the first earthquake to be surveyed by a continuously operating global positioning system gps array the coordinate time series of seven sites are evaluated for station displacements during an interval of 100 days centered on the day of the earthquake we employ a new spatial filtering technique that removes common mode errors from the coordinate time series this approach provides precise estimates of site specific displacements compared to the cumbersome method of analyzing baselines between pairs of stations all sites indicate significant coseismic horizontal displacements of 5 65 mm with uncertainties of 1 2 mm horizontal displacements are in general agreement with elastic dislocation models in particular for sites closer to the epicenter vertical displacements range from 13 to 7 mm with uncertainties of 2 4 mm the observed vertical displacements in all cases show 5 10 mm more subsidence than expected from geodetic and seismic geologic models significant postseismic horizontal displacements totaling 6 2 mm 10 20 of the coseismic displacement are detected at the three sites closest to the epicenter these displacements are modeled as a short term exponential relaxation with a decay time of 22 10 days superimposed on a longer term linear interseismic trend scaling the observed coseismic and postseismic displacements at one of the sites with the distance to the epicenter provides a measure of site strain which agrees well with the direction and magnitude determined from more precise laser strain meter data the time series do not show any detectable preseismic displacements

aquifer mechanical properties and decelerated compaction in tucson arizona in recent decades high groundwater extraction rates often coincident with periods of severe drought result in the widespread decline of water levels overexploitation of aquifers also causes land subsidence which poses a severe threat to infrastructure tucson arizona experiences land subsidence coupled with the depletion of groundwater a critical water resource for the desert city to understand the spatiotemporal evolution of land subsidence and its implications for aquifer properties we examine long time series of surface deformation and head levels measurements at extensometer stations indicate rapid compaction of fine grained material up to 8 5 mm yr from 1990 to 2005 which results in permanent storage volume losses up to 4 1 the analysis of densely populated sets of interferograms generated from envisat and radarsat c band acquisitions yields multitemporal maps of surface deformation at unprecedented resolution these maps reveal that subsidence significantly slows by the late 2000s corresponding with the implementation of artificial recharge efforts subsequent to groundwater level recovery we observe a brief 6 6 year interval of residual compaction suggesting a high vertical hydraulic conductivity which is then shown to be up to 9 8x10 4 m day we also estimate the average elastic and inelastic skeletal storage coefficients for the aquifer system to be 3 78x10 3 and 6 01x10 3 respectively insar shows deformation nearly ceases by 2015 likely reducing hazards associated with earth fissuring and infrastructure damage this study highlights successful outcomes of water management and conservation plans that preserve existing groundwater reserves and increase artificial recharge

mapping regional land displacements in the venice coastland by an integrated monitoring system abstract an original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters wetlands farmlands urban and industrial centers usually reduces the efficiency of single ground based and satellite based measuring techniques five different methods i e spirit leveling differential global positioning system dgps continuous gps cgps interferometric synthetic aperture radar insar and interferometric point target analysis ipta are integrated into a subsidence integrated monitoring system sims to overcome the limits characterizing each technique the sims has been used over the past decade to provide a new image of the land displacements in the venice region the result exhibits a resolution never obtained before the central lagoon including the city of venice shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm year the sinking rates increase up to 10 15 mm year in the coastland south of the lagoon relatively small uplifts less than 1 mm year are observed at the alpine foothills and in a wide area comprised between the euganean hills and the lagoon the observed land displacements have been associated to the geological features of the study region i e tectonics seismicity differential consolidation of the middle upper pleistocene and holocene deposits and to anthropogenic activities such as land reclamation and groundwater withdrawal

understanding the subsidence process of a quaternary plain by combining geological and hydrogeological modelling with satellite insar data the acque albule plain case study abstract this paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages the study area is located about 20 km east of rome italy and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level extensive processing at different scales of sar satellite images ers and envisat provided by esa in the frame of a cat 1 project by means of a dinsar technique was performed the time histories of ground displacements have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades as the response to the anthropic stress based on a large piezometric dataset this comprehensive dataset allowed us to describe the space and time distributions of the subsidence process the spatial pattern and deformation rate change is attributed to the following causes i the changes in the groundwater levels due to the intensification of mine exploitation requiring dewatering operations and ii the distribution and thickness of recent compressible deposits specifically it is derived that the groundwater level variations drive the timing of subsidence triggering over the area whereas the local geological conditions control the magnitude of the deformation process

evidence of local sourcing of sulfur and gold in an archaean sediment hosted gold deposit abstract determining the source of sulfur in an ore deposit is key to understanding the nature of the ore forming processes the neoarchaean paulsens sediment hosted gold deposit 1 moz 7 6 g t located in the pilbara craton of western australia exhibits many of the characteristics of phanerozoic shale hosted gold deposits e g huijiabao trend northern carlin trend and sukhoi log in that 1 black shales are the dominant host rock 2 gold is hosted in pyrite as both free gold and dissolved gold in the lattice of the pyrite and 3 multiple generations of pyrite have formed due to a variety of geological processes in this contribution we utilised secondary ion mass spectrometer sims to measure the in situ quadrupole 32 s 33 s 34 s and 36 s sulfur isotope compositions of the different generations of pyrite our results indicate that the both diagenetic and hydrothermal pyrite generations display similar and anomalous 33 s signatures up to 0 4 further the 33 s 36 s arrays in the hydrothermal pyrite generations lie on a slope which is similar to that of the diagenetic pyrite these data support the hypothesis that the sulfur in the ore zones came from the host hardey formation black shales we also performed trace element analyses of syn sedimentary and early diagenetic pyrite from the hardey formaiton using nano secondary ion mass spectrometry nanosims electron probe microanalysis epma and laser ablation inductively coupled plasma mass spectrometry la icpms all of which show that the syn sedimentary and early diagenetic pyrite contain high concentrations of many trace elements as ni co cu ag se te bi including up to 1 5 ppm au these metals contents are also abundant in the several generations of mineralised hydrothermal pyrite and form clear patterns of growth associated with couple dissolution reprecipitation reactions these findings clearly indicate that the fluid that transported the au must have also been enriched in the base and precious metals that are contained in the early syn diagenesis pyrite data from this study clearly support the hypothesis that in some sediment hosted gold systems all the sulfur and gold required to form the deposit are sourced from the local sedimentary package by using the presence of anomalous mass independent sulfur isotope signatures as chemically conservative and indelible tracers it is possible to fingerprint the source of sulfur in a wide range of mineral systems thus enhancing predictive exploration strategies at the regional to camp scales

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

volcano tectonic and geochemical evolution of an oceanic intra plate volcano tahiti nui french polynesia abstract geological mapping accurate k ar dating and geochemical analyses of lavas allow a detailed reconstruction of the geological history of tahiti nui island french polynesia the exposed volcanic activity is first characterized by the construction of a main shield from 1 4 ma to 870 ka with a maximum aerial eruptive rate around 2 km3 kyr lavas from this early building stage are alkaline slightly silica undersaturated with 87sr 86sr and 143nd 144nd compositions rather constant and close to the enriched mantle ii type vent locations were first concentrated along a main e w rift zone which was responsible for the lateral collapse of the northern and southern flanks of the main shield around 0 87 ma ago the subsequent activity was first restricted to the northern depression corresponding to an eruptive rate of about 5 km3 kyr in the period 850 760 ka significant variations in la sm 87sr 86sr and 143nd 144nd occur in lavas erupted immediately after the main northern landslide indicating a sudden increase in the extent of partial melting likely caused by the decompression subsequent to collapse however the later activity declined and the lavas exhibit a gradual change toward strongly silica undersaturated basanites likely indicating a decreasing extent of partial melting of the upper mantle the evolution of radiogenic isotope ratios over time indicates a change in the source toward more depleted compositions until around 500 ka post erosion volcanic activity following an apparent hiatus of 240 kyr exhibits similar major and trace element and isotope compositions the volcano structural and geochemical evolution of tahiti nui and the overall alkaline character of the lavas from other eruptive complexes of the society alignment suggest a relative weakness low temperature and low eruptive rate of the society plume compared to the hawaiian hot spot

sar monitoring of progressive and seasonal ground deformation using the permanent scatterers technique spaceborne differential radar interferometry has proven a remarkable potential for mapping ground deformation phenomena e g urban subsidence volcano dynamics coseismic and postseismic displacements along faults as well as slope instability however a full operational capability has not been achieved yet due to atmospheric disturbances and phase decorrelation phenomena these drawbacks can often be at least partially overcome by carrying out measurements on a subset of image pixels corresponding to natural or artificial stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data this approach allows one to push the measurement precision very close to its theoretical limit in the order of spl sim 1 mm for c band european remote sensing ers like sensors in this paper the detection of both time uniform and seasonal deformation phenomena is addressed and a first assessment of the precision achievable by means of the ps technique is discussed results highlighting deformation phenomena occurring in two test sites in california are reported fremont in the southern bay area and san jose in the santa clara valley

an overview of chalcophile element contents of pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge sulfide deposits we have compiled the trace element concentrations in pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge ore deposits with the aim of understanding their petrogenesis and whether these minerals can be used as indicator minerals among the samples there are some of the most studied world class ni cu aguablanca duluth jinchuan noril sk talnakh kharaelakh sudbury voisey s bay and others and pge dominated bushveld lac des iles stillwater great dyke and penikat deposits crustal assimilation may be constrained using as se and sb se ratios in pentlandite the degree of interaction between the silicate and sulfide liquids r factor can be estimated by the content of highly chalcophile elements dsulf liq sil liq above 1000 in sulfide minerals the fractional crystallization of the sulfide liquid can be traced using se te ratios of pentlandite pyrite formed by exsolution from mss has higher rh ru ir and os than co existing pyrrhotite whereas pyrite formed by hydrothermal alteration of pyrrhotite inherits the rh ru ir and os contents of the pyrrhotite it replaced sulfide minerals are preserved in transported glacial cover and their trace element chemistry can be used to discriminate their source pentlandite from ni cu deposits has much lower rh and pd concentrations than those from pge dominated deposits pyrite from magmatic deposits has higher co sb and se as ratios relative to pyrite from hydrothermal deposits and chalcopyrite from magmatic deposits has much higher ni and lower cd concentrations than those from hydrothermal deposits

reply to comment by p teatini et al on recent subsidence of the venice lagoon from continuous gps and interferometric synthetic aperture radar 1 unlike most published scientific comments the comment submitted by p teatini l tosi and t strozzi on bock et al 2012 does not dispute the scientific merits of our study but rather reinforces its approach and main results regarding venice subsidence their main points appear to be that our study 1 did not cite the two last papers that they published tosi et al 2010 teatini et al 2012a 2 received considerable attention worldwide for a rather small level of subsidence 3 used a methodology that is not original 4 misrepresented some of their earlier work and 5 published uncertainties that were too optimistic

terrasar x reveals the impact of the mobile barrier works on venice coastland stability land subsidence and eustacy concurred to make the relative sea level in venice italy 23 cm higher over the last century in order to protect the city and its lagoon environment from increased flooding a series of mobile barriers are under construction at the three inlets of lido malamocco and chioggia connecting the adriatic sea to the inner water body since 2003 work has been proceeding with the reinforcement and extension of the existing jetties and the construction of breakwaters harbors and a small island within the lido inlet we detected significant local settlements of a few centimeters between march 2008 and january 2009 at the three inlets induced by the construction works through an interferometric analysis of 30 satellite radar images acquired by the new german terrasar x mission on a more regional scale we observe that the city of venice and the other major urban settlements on the lagoon littorals are not impacted by subsidence during this period the very high spatial resolution of 3 m and the short repeat time interval of 11 days of terrasar x enable the investigation of displacements with an unprecedented observed level of details opening new perspectives to geodynamic s research and civil engineering sectors for the monitoring of large infrastructures with potential vulnerability to terrain motion