the results of the taormina 2006 seismic survey possible implications for active tectonics in the messina straits abstract the straits of messina and its surroundings are considered as one of the most tectonically active area of the mediterranean but in spite of their hazard potential modern geophysical data aimed at investigating their hidden structures are lacking in order to bridge this gap we carried out a marine multichannel seismic survey primarily aimed at i studying the regional fault pattern in the area of the messina 1908 earthquake and ii checking the existence of a potentially seismogenic fault the taormina fault which many authors locate offshore along the coast between taormina and messina our seismic profiles show a great structural complexity within the messina straits with the best imaged faults occurring on the calabrian side in particular a more than 30 km long nw trending fault located at the sw tip of calabria is cutting the sea floor moreover our data did not image any extensional fault plane attributable to the taormina fault rather the whole slope has been tilted east ward the geodynamic implication is that extension in south eastern sicily on the ionian side of the hyblean plateau and extension in southern calabria and messina straits belong to two different tectonic systems and cannot be mechanically linked

time resolved seismic tomography detects magma intrusions at mount etna the continuous volcanic and seismic activity at mount etna makes this volcano an important laboratory for seismological and geophysical studies we used repeated three dimensional tomography to detect variations in elastic parameters during different volcanic cycles before and during the october 2002 january 2003 flank eruption well defined anomalous low p to s wave velocity ratio volumes were revealed absent during the pre eruptive period the anomalies trace the intrusion of volatile rich 4 weight percent basaltic magma most of which rose up only a few months before the onset of eruption the observed time changes of velocity anomalies suggest that four dimensional tomography provides a basis for more efficient volcano monitoring and short and midterm eruption forecasting of explosive activity

geochemical characteristics and magma fertility for the jurassic arc rocks in the gangdese belt tibet abstract jurassic arc magmatic rocks are widely distributed along the gangdese belt southern tibet however only one jurassic arc related porphyry cu deposit the xietongmen deposit has been found the jurassic arc magma fertility needs to be further constrained in order to understand the rarity of arc related porphyry cu deposits in this belt this paper seeks to combine new data on the jurassic granitoid rocks with all published data on the jurassic magmatic rocks in the gangdese belt to comprehensively explore their geochemical variation and magma fertility our new data show that the jurassic granitoid rocks have zircon u pb ages of 171 6 1 1 ma to 195 3 1 3 ma these jurassic granitoids are calc alkaline series with sio2 contents of 59 4 to 70 7 wt mg values of 35 to 53 and a cnk values of 0 72 1 25 mainly 20 v sc ratios 8 and high zircon eun eun 0 3 ce4 ce3 ratios 300 and low titanium in zircon temperatures

geology mineralogy and chemistry of lateritic nickel cobalt deposits near kalgoorlie western australia in the kalgoorlie area of western australia significant deposits of ni co laterite are developed on large ultramafic complexes at siberia and bulong the ultramafic rocks form part of extensive archean greenstone belts in the granitoid terrain of the southeastern yilgarn block and were lateritized during late cretaceous to early tertiary times the laterite profile developed over serpentinized dunite and peridotite is divided into four zones on the basis of morphology mineralogy and chemical composition in the oxidized bedrock zone ni rich saprolitic serpentine and smectite are developed in joints and fractures in the bedrock the overlying saprolite zone consists predominantly of saprolitic serpentine and may retain bedrock structures and textures it is characterized by a decrease of mg and an increase in ni upward a well defined clay zone is commonly developed over the bulong saprolite zone the clay zone is composed essentially of nontronite and quartz and commonly contains ni values of 1 to 2 percent the limohire zone occurs at the top of the profile and may consist of an upper hematite rich section and a lower goethite rich section the limonite zone is rich in fe al and cr and is formed by residual concentration of stable oxides a concentration of mn oxides commonly containing high co and ni grades occurs at the base of the limonite zone where sufficiently thick co and ni rich mn concentrations have been mined for direct smelter feed to augment co and ni production from kambalda ni sulfides physical and chemical characteristics of the underlying bed rock are important controls on the distribution of ni and co accumulations the mode of occurrence of ni and the presence of co are significant factors in the economics of exploiting these deposits

the deformation offshore of mount etna as imaged by multichannel seismic reflection profiles abstract despite the clear evidence of active flank dynamics that is affecting the eastern side of mount etna the contribution of tectonic processes has not been yet understood so far the various models proposed to explain the observed flank deformation have been based on onshore structural data coming from the volcanic edifice the ionian offshore of mount etna has been only recently investigated using multichannel seismic profiles and offers the opportunity to image the structural features of the substrate of the unstable flank of the volcano this contribution aims at describing the deformation located offshore mount etna using multichannel seismic profiles recently acquired during three seismic surveys the onshore flank deformation of mount etna appears to be laterally confined by two tectonic guidelines trending roughly e w located to the north and south of the deforming flank the northern guideline in particular takes the surface expression of a sharp fault pernicana fault though often assumed that these boundary structures continue offshore as linear features connected to a frontal thrust ramp the occurrence of this simple offshore structural system has not been imaged in fact seismic data show a remarkable degree of structural complexity offshore mount etna the pernicana fault for instance is not continuing offshore as a sharp feature rather the deformation is expressed as ene wsw folds located very close to the coastline it is possible that these tectonic structures might have affected the offshore of mount etna before the pernicana fault system was developed less than 15 ka ago the southern guideline of the collapsing eastern flank of the volcano is poorly expressed onshore and does not show up offshore in fact seismic data indicate that the catania canyon a remarkable e w trending feature does not reflect a tectonic control seismic interpretation also shows the occurrence of a structural high located just offshore the edifice of mount etna whereas a complex deformation affects the boundary of this offshore bulge it shows only limited internal deformation part of the topography of the offshore bulge pre existed the constructional phase of mount etna being an extension of the hyblean plateau only in the northern part the bulge is a recent tectonic feature being composed by plio quaternary strata that were folded before and during the building of mount etna the offshore bulge is bounded by a thrust fault that can be related to the intrusion of the large scale magmatic body below mount etna

evolution of volcanism around the eastern sector of mt etna inland and offshore in the structural framework of eastern sicily abstract the authors highlight a new perspective to understanding the volcanism in the mt etna eastern sector inland and offshore based on original studies of the sea floor off the ionian coast of etna by means of various direct surveying methods underwater explorations and indirect ones bathymetric reconstructions using echosounders they also propose a new interpretation of geophysical geochemical and structural surveys carried out over the last two decades results show that eastern etnean sector s volcanism extends as far as the ionian sea to a maximum distance from the coast of probably about 20 km in their opinion the absence of outcropping apparatuses in the lower eastern flank of etna is due to these apparatuses being buried by a large detritic formation chiancone due to the dismantling of the ancient alkaline centres aac localised to the west the authors consider the structures highlighted by the study of the digital elevation model dem of the ionian sea floor and by the multibeam analysis marani et al 2004 from seafloor to deep mantle architecture of the tyrrhenian backarc basin vol 44 mem descr carta geol ital pp 1 2 to be of a volcanic nature this hypothesis opens up a new field of study within the evolution of the eastern etnean edge s volcanism inland and offshore in the last 500 ky and would further confirm the eruptive axes migration from east to west

early messinian manganese deposition in ne cyprus related to cyclical redox changes in a silled hemipelagic basin prior to the mediterranean salinity crisis abstract unusual bedded manganese deposits occur within hemipelagic carbonates dated as early messinian 5 97 ma based on calcareous nannofossils these sediments accumulated during a time of increased isolation of the mediterranean sea from the atlantic ocean but prior to major sea level fall and evaporite precipitation during the messinian salinity crisis the manganese deposits form six main laterally continuous beds up to 70 cm thick compositionally they are dominated by poorly crystalline manganese oxide birnessite with associated mild enrichment in some trace elements e g ba ni cu mo as u background minerals include magnesian carbonate kaolinite chlorite mixed layer clays and talc serpentinite derived a tectonically controlled deep water basin existed to the south of a topographic ridge future kyrenia range in which seawater alternated between oxidising and oxygen depleted at depth orbital precession influenced the weathering of continental source areas that included basic igneous rocks and some pre existing hydrothermal deposits after entering the basin via land runoff manganese was retained in solution below the chemocline during stagnant low oxygen periods manganese oxide and associated trace elements e g mo u precipitated in response to cyclical seawater oxidation to form manganese rich layers up to layers with up to with up to c 30 mno to reach these very high concentrations soluble manganese may have fluxed upwards from an anoxic environment represented by early messinian sapropels manganese precipitation events diminished with time giving way to well oxygenated hemipelagic marl accumulation with a shelly infauna gypsum appears abruptly upwards above the marls in adjacent sections the mn deposition mainly represents an interplay between tectonically controlled basin formation chemically favourable source climatic conditions possible sea level change effects and likely diagenetic manganese enrichment the regional tectonic setting relates to early stage collision of the african and tauride eurasian plates

very shallow earthquakes and brittle deformation in active volcanic areas the eatnean region as an example abstract some aspects of the stress field acting in active volcanic areas were investigated by studying the relationship between surficial seismicity h 1 2 km and the brittle deformation pattern of the etna volcano the magmatic composition and structural character of mt etna are described together with its geodynamic regional context after a discussion of the problem of the state of stress in active volcanoes and a definition of very shallow seismicity the high level of surficial seismicity the morphology of the sedimentary basement and the kinematic behaviour of the faults suggest that the eastern flank of mt etna is a shallow seismotectonic domain structurally decoupled from the rest of the volcanic body this flank shows a tendency to slide in an eastern direction and is bound to the north by a left lateral oblique slip normal fault trending e w and in the south by an arcuate fault system with right lateral features right lateral oblique slip normal faults

link between major flank slip and 2002 2003 eruption at mt etna italy 1 the 2002 2003 etna eruption is studied through earthquake distributions and surface fracturing in september 2002 earthquake induced surface rupture sinistral offset 0 48 m occurred along the e w striking pernicana fault pf on the ne flank in late october a flank eruption accompanied further 0 77 m surface rupturing reaching a total sinistral offset of 1 25 m the deformation then propagated for 18 km eastwards to the coastline sinistral offset 0 03 m and southwards along the nw se striking timpe dextral offset 0 04 m and later trecastagni faults dextral offset 0 035 m seismicity 4 km bsl on the e flank accompanied surface fracturing fault plane solutions indicate an overall ese wnw extension direction consistent with ese slip of the e flank also revealed by ground fractures a three stage model of flank slip is proposed inception september earthquake climax accelerated slip and eruption and propagation e and s migration of the deformation

late quaternary slip rates on the acireale piedimonte normal faults and tectonic origin of mt etna sicily abstract mt etna is located along the east coast of sicily near the boundary between the continental crust of the hyblean plateau and the mesozoic oceanic crust of the ionian basin the main active faults near mt etna cut the base of its eastern flank forming a 30 km long system of nne and nnw trending ene chelon fault segments the acireale piedimonte system showing dip slip and oblique right lateral motion most segments are associated with shallow depth seismicity and all have late pleistocene to holocene vertical slip rates ranging between 1 and 2 mm yr typical of major active normal faults worldwide eruptive fissures arranged in nne to ne trending zones cut the highest slopes of the volcano on the footwall of the normal fault system structural analysis suggests that current motions along both the active faults and eruptive fissures are kinematically compatible and simply linked with ongoing wnw ese directed regional extension such extension characterizes at a greater scale the active tectonics of southern italy where all large shallow historical earthquakes have remained confined within a narrow normal fault belt or rift zone stretching from the northern calabrian arc to southeastern sicily the southernmost west dipping faults of that rift zone in calabria aspromonte cut across the calabro peloritan thrust belt to join the mostly east dipping acireale piedimonte faults along the western boundary of ionian oceanic lithosphere which continues southwards as the malta escarpment we thus relate magmatism at etna to dilational strain on the footwall of an east facing crustal scale normal fault at the bend where the siculo calabrian rift zone veers 60 eastwards as it begins to cross the calabrian arc leaving the east facing margin of the ionian sea to catch up with the west facing margin of the tyrrhenian sea farther north

cryptomelane a tool to determine the age and the physical chemical regime of a plio pleistocene weathering zone in a granitic terrain hagendorf se germany abstract cryptomelane a k mn bearing oxide is widespread in the lowermost part of the weathering supergene alteration zone of the hagendorf pegmatite se germany this supergene mn mineral has been used in the present study for k ar dating of weathering and paleohydraulic processes as young as plio pleistocene different cryptomelane age data found in the same weathering and paleohydraulic system resulted from continuous hydraulic processes in the weathering system rather than from a stepwise uplift that shaped the landscape in the granitic area of the ne bavarian basement an almost pure cryptomelane mineralization is indicative of the basal zone of supergene alteration because a complete separation of mn from fe can favorably be achieved only in the infiltration zone under slightly reducing conditions or in the percolation zone under slightly oxidizing conditions cryptomelane is precipitated under slightly oxidizing conditions from alkaline solutions in the percolation zone and cast as a marker for fluctuating paleo water levels manganese oxides uranyl phosphates and silicates were found at different depths in the weathering zone of this granitic terrain they were dated by different dating methods k ar and u pb and yielded the same age of formation consequently the 4 ma signal of both groups of supergene minerals has geomorphological and paleohydraulic connotation and is related to a unique geomorphological process the pliocene peneplanation gradual hydraulic adjustments gave rise to the younger pleistocene age found at shallow depth in the weathering zone

geological evolution of mount etna volcano italy from earliest products until the first central volcanism between 500 and 100 ka ago inferred from geochronological and stratigraphic data we present an updated geological evolution of mount etna volcano based on new 40ar 39ar age determinations and stratigraphic data integrating the previous k ar ages volcanism began at about 500 ka ago through submarine eruptions on the gela catania foredeep basin about 300 ka ago fissure type eruptions occurred on the ancient alluvial plain of the simeto river forming a lava plateau from about 220 ka ago the eruptive activity was localised mainly along the ionian coast where fissure type eruptions built a shield volcano between 129 and 126 ka ago volcanism shifted westward toward the central portion of the present volcano val calanna moscarello area furthermore scattered effusive eruptions on the southern periphery of etna edifice occurred until about 121 ka ago the stabilization of the plumbing system on the valle del bove area is marked by the building of two small polygenic edifices tarderia and rocche volcanoes their eruptive activity was rather coeval ending 106 and 102 ka ago respectively during the investigated time span volcanism in etna region was controlled by a main e w extensional tectonic related to the reactivation of malta escarpment fault system in eastern sicily

recent seismicity and tomographic modeling of the mount etna plumbing system the monitoring of seismic activity in eastern sicily southern italy has been recently improved in the framework of the poseidon project to investigate both tectonics and volcanic processes of mount etna this effort has produced a homogeneous and complete data set which we use to image the deep structure of the volcano and to define the space and time distribution of the recent seismicity encompassing the 1995 eruption diffuse eruptions between 1995 and 1997 a further magma intrusion started in 1997 and an increase of volcanic activity in july 1998 we inverted p wave arrival times from 307 selected local earthquakes to obtain a three dimensional velocity model of the volcano with a simultaneous inversion for hypocenters and velocity parameters the new tomographic images permit us to define the structure beneath the volcano from the surface down to 18 km depth the main structural feature revealed by our inversion is a high velocity body located beneath the central craters whose lateral extent increases from 6 km between 18 and 9 km depth to 12 km between 9 and 3 km depth near the surface the fast anomaly branches in two separate high vp regions which are located below the summit craters and the eastern flank valle del bove respectively the high velocity features are interpreted as high density cumulates of solidified magma that intruded the shallow crust we hypothesize that magma ascends the crust within the relatively small high velocity conduit below 9 km depth and is stored at depth shallower than 9 km within the broad high velocity region as also suggested by petrological data a sharp increase of seismicity in 1997 with earthquakes occurring at the border of the high velocity body suggests that mount etna sustained recent episodes of intrusions which possibly herald future eruptions no large low velocity anomaly interpretable as a melted magma chamber is imaged in the upper 18 km of the crust while a broad low velocity anomaly in the uppermost mantle revealed by regional seismic data possibly indicates the magma source region at depth earthquake occurrence from the deep source to the shallow intrusive area helps to trace the magma migration and the feeding of the volcanic system

new simulations and understanding of the 1908 messina tsunami for a dual seismic and deep submarine mass failure source abstract over 100 years after the event the mechanism of the 1908 messina tsunami remains unresolved the up to 12 m runups observed along the coasts of sicily and calabria cannot be explained by the coseismic tsunami so recent studies have proposed a dual earthquake submarine mass failure smf mechanism here we propose a new dual source and use it to simulate tsunami generation with a three dimensional non hydrostatic model coupled to a two dimensional fully nonlinear and dispersive model to simulate tsunami propagation to shore we first reanalyze observations of tsunami arrival times from eyewitnesses acquired shortly after the 1908 event and a tsunami record at a tide gauge in malta similar to earlier work this data is used to locate the likeliest tsunami source area by inverse wave ray tracing but accounting for frequency dispersion effects on wave celerity uncertainty in reported arrival times and a time delay between the eq and smf triggering analyzing the seafloor morphology in this area we identify a new smf at the foot of the fiumefreddo valley northeast of mount etna the general location is consistent with earlier studies however our smf is much smaller 2 km3 than e g that of billi et al 2008 and is a fairly rigid block slump rather than a translational smf we model the block motion and simulate tsunami generation from a dual eq smf source and its propagation to shore in higher resolution grids and based on more accurate bathymetry and topography than in earlier work runups and travel times agree well with observations except for runups on either side of the messina straits north of the smf which are still underpredicted in the far field simulations reproduce well the arrival time and initial wave amplitudes at the malta tide gauge our newly parameterized smf and modeling improve tsunami runups simulated near the smf location and south of it however as with all previous modeling of this event additional sources are required to explain runups in the northern messina straits which we suggest might be smaller and shallower smfs located in this area these will be considered in future work

seismic heterogeneity of mt etna structure and activity a dense seismic array maintained temporarily for 7 weeks provides an approach to deducing the 3 d heterogeneity of the structure of the upper crust beneath mt etna volcano from the inversion of p and s wave arrivals of local earthquakes independent data from a different source array geometry using waves generated by distant shots at sea confirm a main lateral variation a high velocity body underlies part of the volcano its contrast with the surrounding thick sedimentary pile and its location extending from the present summit to the southeast suggests that it may have been built by the development and migration of past eruptive centres followed by caldera collapse local low velocity anomalies near its sharp western edge may be associated with presently active features

dynamics of the eastern flank of mt etna volcano italy investigated by a dense gps network abstract mount etna has developed at the intersection of two regional tectonic lineaments the nnw sse trending hybleo maltese escarpment which separates the thick inland continental crust of the african platform from the ionian mesozoic oceanic crust and the ne sw messina fiumefreddo fault that marks a rift zone between south calabria and north eastern sicily extending as far as the mt etna area all tectonic features affect with outstanding surface features the eastern side of the volcano the eastern flank of the volcano is affected by a long term motion toward ese in 1997 in order to increase the detail of the ground deformation pattern on the lower eastern flank of mt etna a new gps network the ionica network was installed on this sector of the volcano this gps network consists of 24 stations and covers the lower eastern flank of the volcano from the town of catania to taormina and from the coastline up to an altitude of about 1300 m all the new stations consist in self centring benchmarks this kind of benchmark allows all station set up errors to be avoided before the merging of the ionica network to the frame of the global gps network of mt etna in june 2001 three surveys were carried out on this network in september 1997 august 1998 and january 2001 from the ground deformation pattern it is possible to distinguish two different sectors showing different characteristics of deformation the southern part of the network shows a more uniform distribution of the vertical motion with a mean se ward horizontal component while the northern one shows an heterogeneous vertical motion with a ese ward horizontal component furthermore a higher velocity is detected between 1997 and 1998 due to the additional stress induced by a shallow intrusion on the nw flank of the volcano the model resulting from data inversions defines a wide sliding plane beneath the entire eastern flank of the volcano with a low dip angle the expected velocity vectors fit well the observed ones even if the measured velocities are still quite higher than expected at lowermost stations the vertical inclination of the velocity vectors measured during the 1998 2001 period gradually decreases from west to east suggesting a sort of rotational movement of the south eastern flank interrupted by some anomalous vectors on the lower part that show higher vertical velocities these anomalies being located on a wedge defined by the intersection of the main nnw sse and ne sw fault systems and near the timpe faults are probably due to the activity of the vertical faults cutting the lower eastern flank of mt etna stations lying on the hanging wall and on the footwall of the timpe fault system are affected by similar horizontal displacements meaning that these structures are moving eastwards together with the sliding flank this evidence suggests that the timpe faults are probably second order structures with respect to the detachment surface these results depict a structural framework of the eastern flank of mt etna in which the low angle dislocation can be considered as a first order approximation of an actual listric plane and the current active part of the timpe fault system is confined above the detachment surface

comment on on the cause of the 1908 messina tsunami southern italy by andrea billi et al 1 the december 28th 1908 messina earthquake has been ranked as one of the most destructive events of the last centuries davison 1936 the damages produced by ground shaking were aggravated by the effects of a remarkable tsunami with up to 11 m of run up height that followed the earthquake omori 1909 baratta 1910 tinti et al 2004 the location of the causative fault is still a matter of debate e g argnani et al 2009 the modelling of the associated tsunami tinti and armigliato 2003 allowing uncertainty 2 billi et al 2008 have recently proposed that the tsunami that stroke the coast of the strait in december 1908 originated from a large submarine landslide 20 km located offshoregiardini naxos the hypothesis is based on the study of tsunami arrival times platania 1909 baratta 1910 and is supported according to billi et al 2008 by inspection of a multibeam morphobathymetry marani et al 2004 and of a crustal scale seismic profile scrocca et al 2004 3 the arguments of billi et al 2008 however have weak points that cast doubt on their interpretation but most importantly data collected in the last few years by the authors of this comment a argnani and f chiocci and work on tsunami modelling s tinti and his group cast further doubt on the proposed hypothesis that a large submarine landslide that was caused by the 1908 earthquake is located offshore giardini naxos these issues will be discussed in the following

manganese in the s w pacific a brief review abstract manganese occurs as relatively small scale terrestrial deposits throughout the s w pacific and has been mined in vanuatu fiji new caledonia new zealand and papua new guinea listed in order of importance as producers in each case mining has now ceased to be economically profitable present information on s w pacific terrestrial manganese deposits is limited and dated and little work is being carried out no modern synthesis of these deposits or their mode of genesis exists data on the manganese distribution in soils are sparse in the marine environment substantial work has been carried out this review indicates the need for a comprehensive study of manganese ore deposits and manganese in soils in the s w pacific with a particular emphasis on comparison of results from different localities and settings

large submarine landslides offshore mt etna 1 high resolution seismic data we collected in the ionian sea reveal large submarine landslide deposits offshore from mt etna italy spatially consistent with the eastern flank collapse of this volcano a large debris avalanche deposit we relate to the valle del bove scar displays long offshore run outs till 20 km and a volume of a few tens of cubic kilometres 16 21 km 3 other landslide deposits are also imaged in particular a striking unique record of the relative timing of multiple submarine large slump events

seismological features of the pernicana provenzana fault system mt etna italy and implications for the dynamics of northeastern flank of the volcano abstract the pernicana provenzana fault system is one of the most active tectonic systems of mt etna and it plays an important role in the dynamic of the eastern flank of the volcano earthquakes occurring close to this structural trend have reached magnitudes up to 4 2 sometimes with coseismic surface faulting and have caused severe damages to tourist resorts and villages in the vicinity of this structure in the last decade a large number of shocks sometimes in the form of swarms linked to pernicana provenzana fault system movements have been detected by the permanent local seismic network operating in eastern sicily in this paper we report on the detailed study of the seismic activity occurring during the 2000 2009 time span in the pernicana provenzana fault system area firstly we located 407 earthquakes using a standard location code and a 1d crustal velocity model we then applied two different approaches to calculate precise hypocenter locations of the events in particular a non linear code was adopted to obtain an estimate of the a posteriori probability density function in 3d space for the hypocenter location moreover a relative location of correlated event pairs was performed using the double difference method these two different location approaches allowed defining with good accuracy the most active and hazarding sectors of the structure the results of these precise locations showed a tighter clustering in the epicenters and in focal depths in comparison with standard locations earthquakes are located along the pernicana provenzana fault system and are mainly clustered in two zones separated by an area with very low rate of earthquakes occurrence but characterized by the highest energy release depths of the foci are very shallow ranging between the surface and about 3 km b s l kinematics of the pernicana provenzana fault system revealed by the fault plane solutions computed for the most energetic earthquakes highlights a predominant dip slip and left strike movements along e w oriented fault planes in agreement with field observations

iron isotopes constrain biogeochemical redox cycling of iron and manganese in a palaeoproterozoic stratified basin abstract the hotazel formation in the uppermost stratigraphic portion of the neoarchaean palaeoproterozoic transvaal supergroup of southern africa is an unusual sedimentary sequence of banded iron formation bif intercalated with three manganese rich layers as such it is a succession that holds great potential to offer a unique view of one of the most dramatic transitions in early earth history the switch to a full oxidative cycle in shallow oceans at ca 2 3 ga we present iron isotope results from bif and mn rich samples collected across the entire hotazel sequence with a view to constraining processes of biogeochemical redox cycling for both metals close to the transition from a reducing to an oxidizing ocean atmosphere system the recorded de coupling of fe and mn reduction during anaerobic organic carbon cycling in the hotazel strata suggests that manganese became an important electron acceptor in stratified marine environments of the palaeoproterozoic during periods of increased primary manganese precipitation relative to iron very low 57fe values registered across the entire hotazel sequence and especially in manganese rich samples 2 4 to 3 5 signify deposition of iron and manganese in a terminal stratified aqueous reservoir that was depleted in the heavy iron isotopes these isotopic signatures in conjunction with the unusual endowment of the hotazel sequence in manganese are interpreted to have evolved by rayleigh distillation processes during protracted deposition of mn poor bifs as preserved in the lower stratigraphic portion of the transvaal supergroup kuruman and griquatown bifs the unique end member geochemical and isotopic characteristics of the hotazel rocks may therefore constitute a potential link between the widespread deposition of bif during the neoarchaean and palaeoproterozoic and the postulated rise in atmospheric oxygen levels around 2 3 ga ago

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

the hydrothermal component in ferromanganese nodules from the southeast pacific ocean abstract statistical analyses of geochemical data from ferromanganese nodule samples representing a broad area of the southeast pacific ocean indicate nodule compositions are controlled by four factors 1 suboxic diagenesis 2 oxic diagenesis 3 hydrogenous precipitation and 4 hydrothermal precipitation the first three are identical to those identified in studies of nodules from the north pacific the fourth factor represents the first quantitative determination of a significant hydrothermal end member in ferromanganese nodules nodules apparently acquire a hydrothermal component through the accretion of colloidal sized hydrothermal precipitates which are widely dispersed from their origin at vents along the east pacific rise epr nodules recovered from beneath the shadow of the present day hydrothermal plumes emanating from the epr contain significantly higher amounts of hydrothermal material relative to nodules from other areas

magma storage eruptive activity and flank instability inferences from ground deformation and gravity changes during the 1993 2000 recharging of mt etna volcano abstract a long recharging period characterized mount etna volcano during 1993 2000 before the main explosive effusive 2001 and 2002 2003 flank eruptions the joint analysis of ground deformation and gravity data over the recharge period reveals that different phenomena occurred within etna s plumbing system and clearly indicates two phases spanning 1993 1997 and 1997 2000 respectively the first phase was characterized by magma storage and accumulation at an intermediate depth 2 6 km below sea level which provoked overall inflation and positive gravity changes during the second phase the magma started to rise and intrude at shallower levels favoring the movement of the unstable eastern flank which accelerated its sliding toward the east the shallower magma accumulation also caused the gas exsolution associated with increasing explosive activity at the summit craters negative gravity changes were detected during this phase the gravity measurements independent of the same result obtained by geochemical studies suggest that only 20 30 of the magma volumes supplied in the plumbing system were then erupted the complex dynamics of rising magma beneath mount etna makes ground deformation and gravity measurements complementary being able to detect different effects of magma emplacements beneath the surface our results also highlight how the joint use of ground deformation and gravity observations may be crucial in identifying the nature and rate of an impending period of volcanic eruptions

paleoproterozoic manganese and base metals deposits at kisenge kamata katanga d r congo the kisenge kamata manganese deposit katanga d r congo belongs to a group of paleoproterozoic sedimentary manganese ore occurrences that have been recognized for various parts of africa it is a relatively small deposit with total estimated reserves of similar to 12 mt ore but it is of major importance for understanding key aspects of the geology of the kasai block of the congo craton the available constraints indicate that the deposit formed in the 2 0 1 9 ga time interval in the orosirian period the manganese rich facies of the kisenge kamata deposits range in composition from manganese carbonate rocks to non calcareous deposits dominated by manganese rich garnet associated rocks are mainly grey graphitic shales the kisenge kamata sediments are significantly enriched in cu co ni zn and other accessory metals v mo ga field constraints and geochemical data suggest that the kisenge kamata sediments were probably deposited in a relatively small intracratonic basin graben within the kasai block with an inlet allowing periodical access for ocean water influx carrying mn ree and other metals primary carbonate ore has relatively low delta c 13 3 to 6 parts per thousand and high delta o 18 13 to 20 parts per thousand values confirming their derivation from marine fluids

ground and marine magnetic surveys of the lower eastern flank of etna volcano italy abstract in 1996 and 1997 two high resolution magnetic surveys one on land and the other at sea were carried out on the lower eastern flank of mount etna the magnetic surveys covering an area of about 400 km2 aimed to elucidate the relationships between the main tectonic and morphologic features of this flank of mount etna major features include widespread nnw and nne trending active faults and the valle del bove a depression considered to be the source area of the chiancone deposit the largest etnean volcaniclastic sequence magnetic surveys show anomalies that roughly follow the trend of active main structures although few magnetization measurements are available for the most representative outcrops of the lower eastern side of mount etna interpretation of the anomalies defines the underground geometry of the chiancone deposit and its relationship with volcano stratigraphic units and the underlying sedimentary rocks in particular a volume of about 14 km3 was ascribed to the chiancone deposit such a large amount of material was likely produced by a catastrophic event and deposited at different periods at the exit of the valle del bove in an area produced by the interaction on a regional scale of the main tectonic structures affecting this flank of the volcano

contrasting triggering mechanisms of the 2001 and 2002 2003 eruptions of mount etna italy abstract mount etna produced two significant eruptions in 2001 and 2002 2003 which we have analysed using geological seismic and deformation data these eruptions showed some similarities such as the activating of two magmatic plumbing systems central lateral and eccentric but they differed in their triggering mechanisms while the 2001 eruption was largely the result of the emplacement of a n s eccentric dike independent from the central conduits consistent with e w regional extension the 2002 2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano this is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions during the months prior to the 2001 eruption most epicenters were concentrated on the southern flank at depths of 5 15 km below sea level during the 4 days before the eruption earthquake hypocenters migrated to shallower levels from 5 km bsl upward indicating the emplacement of the eccentric dike this is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements edm in contrast the months before the 2002 2003 eruption were characterised by shallower seismicity mainly concentrated along the active faults bordering the slipping flank sector flank slip accelerated in september 2002 and a second more vigorous acceleration of flank slip occurred on 26 27 october 2002 accompanying the opening of eruptive vents the very short 2 h seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption subsequently flank slip deformation extended all over the eastern and southeastern flanks of the volcano causing serious damage in this sector the events of 2001 2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics magma accumulation and eruption and flank instability in this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip which in turn facilitated the 2002 2003 eruption this sequence of events points to a long term feedback mechanism between magmatism and flank instability at etna

les mineralisations manganesiferes volcano sedimentaires du blafo gueto cote d ivoire parageneses alteration climatique les indices manganesiferes des collines blafo et gueto sont rencontres dans les quartzites et les schistes sericiteux associes aux epanchements rhyolitiques d une serie volcano sedimentaire birrimienne la mineralisation epigenetique est une impregnation d oxydes de fer goethite et de manganese essentiellement mno2 cryptomelane et nsutite surimposee a une paragenese initiale a magnetite pyrophanite et localement ottrelite et grenat l alteration meteorique n a provoque de transformations notables que dans les materiaux associes a deux surfaces d aplanissement l une est conservee sous forme de petits temoins bauxitises au sommet des collines et des minerais enrichis sont associes a la gibbsite et la kaolinite l autre est un glacis de piemont et le manganese s y disperse dans une cuirasse ferrugineuse

chemical evolution of seawater in the transvaal ocean between 2426 ma ongeluk large igneous province and 2413 ma ago kalahari manganese field abstract drill core and outcrop samples of pure marine chemical sediments banded iron formation bif manganese formation mnf jaspilites lutites and cherts from the transition of the 2426 ma old ongeluk formation into the 2413 ma old hotazel formation transvaal supergroup south africa reveal remarkable changes of seawater chemistry in the transvaal ocean similar to pre ongeluk chemical sediments the shale normalized rare earths and yttrium reysn patterns of jaspilites intercalated with the volcanic rocks of the ongeluk large igneous province and directly overlying cherts do not show positive eusn anomalies indicating that high temperature 250 c hydrothermal fluids did not contribute significantly to the rey budget of ambient waters however a 10 cm drill core section in the lower hotazel formation is characterized by conspicuous positive eusn anomalies revealing temporary inflow of water masses strongly affected by high temperature hydrothermal fluids after this short episode the reysn pattern of transvaal seawater returned to that of pre ongeluk times showing heavy reysn enrichment positive lasn gdsn and ysn anomalies but no cesn or eusn anomalies higher up in the stratigraphy the hotazel formation shows negative cesn anomalies in some of the lutites bifs and mnfs reflecting ce depletion in ambient seawater all hotazel lutite bif and mnf samples studied show unradiogenic end t values 0 5 0 2 to 2 4 0 2 indicating a mostly continental rey source the rey distribution and nd isotope data combined suggest that oxidative terrestrial weathering of this continental crustal source supplied most of the dissolved rey to local transvaal seawater precipitation of the hotazel lutites bifs and mnfs with negative cesn anomalies therefore suggests that oxic conditions prevailed on the kaapvaal craton and in hotazel seawater already at 2 413 ga i e 80 m y before the disappearance of mass independent sulfur isotope fractionation mif s that defines the great oxidation event at 2 33 ga

on the cause of the 1908 messina tsunami southern italy 1 a century after the catastrophic event the sources of the 1908 messina southern italy earthquake and tsunami which caused at least 60 000 deaths remain uncertain through a simple backward ray tracing method we convert the tsunami travel time data reported in a 100 years old paper into distances and find that the sources of the earthquake and tsunami are different overturning a long held assumption reconsideration of the available tsunami bathymetric seismic and seismological data indicates that the tsunami was generated by an underwater landslide

manganese deposition through geological time dominance of the post eocene deep sea environment abstract the total terrestrial manganese ore deposits amount to about 6 4 10 9 tonnes of which 5 3 10 9 tonnes 82 are precambrian and 1 1 10 9 tonnes 18 mesozoic and cenozoic deep sea manganese nodules formed since the lower miocene unconformity 12 ma b p hold about 10 11 tonnes mn about 16 times the manganese in terrestrial deposits the development of deep sea manganese nodules is a reflection of global cooling and resulted from the transition of the sluggish cretaceous ocean with warm saline bottom water to the post eocene ocean with cold well oxygenated bottom curents important climatic and oceanographic events occurred at the eocene oligocene boundary and more particularly at the lower miocene unconformity which marks the period of increased antarctic bottom water circulation by contrast the giant shallow water manganese deposits of the lower jurassic to oligocene are associated with anoxia and high sea level stands the two types of deposit reflect different oceanographic conditions and tend not to be contemporaneous mass balance considerations suggest that the present day input of manganese into the oceans is in balance with its deposition in manganese nodules and sediments with perhaps 90 of the input being from hydrothermal sources although this is speculative the scale of present day deep sea manganese nodule formation suggests that we live in the manganese era

late archean initiation of manganese metallogenesis its significance and environmental controls abstract manganese metallogenesis was initiated in a modest scale during the late archean time selectively in india and brazil sedimentary deposits occur in both greenstone belts and high grade granulite terranes in shallow water shelf regimes only and are often intimately associated with stromatolites the changes in the rates of continental crustal growth mantle heat flux and outgassing along with the evolution of tectonic regimes sedimentary environments the state of the biosphere and finally the compositions of interacting atmosphere hydrosphere system from the early to the late archean time have been traced as interdependent parameters and interpreted to explain the first appearance of sedimentary manganese deposits promoted by possibly localized oxygenated environments compared to the spectacular manganese event represented by the giant paleoproterozoic kalahari deposit south africa which is interpreted to have been formed as a consequence of the rapid increase in atmospheric oxygen level ca 2 5 2 4 ga ago the modest initiation of the late archean manganese depositions was triggered by localized photosynthetic oxygen supply forming basin margin oxygen oases as a prologue for the succeeding stratified ocean system the dissolved manganese in the basin water that was oxidized to form shelf type shallow water deposits is suspected by analogy with contemporary banded iron formations bifs but not proved to be of hydrothermal ancestry the initiation of concentrated manganese sedimentation during the late archean by itself provides an evidence for an increase in the oxygen content in the contemporary atmosphere hydrosphere system compared to that in the earlier period supporting the geochemical indications from paleoweathering profiles

dynamics of mount etna before during and after the july august 2001 eruption inferred from gps and differential synthetic aperture radar interferometry data we acknowledge the istituto nazionale di geofisica e vulcanologia the italian dipartimento per la protezione civile and the european community contract ingv dpc ur v3 6 36 and volume project for their economic contribution to this research the sar data are provided by esa esrin

volcano tectonic activity along structures of the unstable ne flank of mt etna italy and their possible origin abstract we describe the prehistoric historic activity of the main and minor volcano tectonic structures of the northeastern flank of mt etna giving new data which provide a clearer view of how destabilized volcanoes react to magma pressure and gravity forces data are mostly based on new lithostratigraphic surveys and on offset measurements of late pleistocene holocene deposits and historic man made features the north east rift ne rift is a volcanic rift that has guided mostly explosive but also secondary effusive activity since the end of the pleistocene monogenetic cones and explosive craters are strongly elongated and aligned along 66 main surface fractures and several others hidden but inferred from sinkhole alignments the opening direction is locally oblique with a left lateral component in the north eastern segment of the rift at the ne tip of the rift the movements are relieved by the normal left lateral pernicana fault pf an 11 km long structure comprising e w fault segments connected by right stepping en echelon faults our study demonstrates that the very high slip rates at a centennial scale of these structures are well constrained and similar ne rift 0 6 1 8 cm a pf 0 5 2 2 cm a and have been also recognized in the latest pleistocene holocene 2 7 cm a the e w fiumefreddo fault ff has normal left lateral kinematics and a historic slip rate of 0 1 cm a ripa della naca faults strike ne and are covered by unfaulted

characteristics of manganese ore deposits in china abstract manganese ore deposits are widely distributed in china based on features of regional tectonics and sedimentary environments as well as genetic characteristics seven important metallogenic provinces can be classified the commercial manganese ore deposits are distributed mainly on platforms and their marginal areas especially those of relatively mobile platforms the main metallogenic epochs of manganese ore deposits of china are sinian and devonian in contrast with the famous proterozoic cretaceous and oligocene manganese deposits elsewhere in the world based on their modes of origin manganese ore deposits in china can be divided into six types among them sedimentary and supergene deposits are the main types accounting for commercial manganese deposits according to the lithological association of the ore bearing series sedimentary manganese ore deposits can be classified into 1 mud rock type 2 black shale type 3 carbonate rock type in addition eight element association types can also be identified among which b mn s mn ca mg mn and p mn types are quite special for manganese ore deposits in china

importance of gravitational spreading in the tectonic and volcanic evolution of mount etna the interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude from small cones to the oceanic crust1 3 although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth it is rarely recognized as such here we describe a striking example of this process at etna volcano in italy the volcano and its clay rich substratum are slowly spreading towards the east and south driven by gravity spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity as gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions an appreciation of its effects could become an essential element of future volcanic hazard evaluation our model proposed here for etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes

structural assessment of mount etna volcano from permanent scatterers analysis a study of the deformation pattern of mount etna volcano based on the results from the permanent scatterers ps technique is reported ground motion data provided by the interferometric synthetic aperture radar insar ps technique from 1995 to 2000 are compared and validated by gps data an analysis of the ascending and descending line of sight los components of ground velocities has yielded detailed ground deformation maps and cross sections this analysis allows detection and constraint of discontinuities in the surface velocity field los velocities have then been combined to calculate the vertical and horizontal e w ground velocities a wide inflation of the edifice has been detected on the western and northern flanks over an area of about 350 km2 a seaward motion of the eastern and southern flanks has also been measured ps data allows the geometry and kinematics of the several blocks composing the unstable flanks to be defined even in the highly urbanized areas and their displacement rates have been measured with millimeter precision this analysis reveals the extension of some features beyond their field evidences and defines new important features the results of this work depict a new comprehensive kinematic model of the volcano highlighting the gravitational reorganization of the unbuttressed volcanic pile on its slippery clay basement on the southern flank but an additional drag force due to a strong subsidence of the continental margin facing the etna volcano is necessary to explain the ps velocity field observed on the eastern flank

roots of etna volcano in faults of great earthquakes abstract results from several seismic methods allow us to sketch the deep structure of etna and its ionian margin under etna a volume of high velocity material is found in a structurally high position the emplacement of this suggests spreading of the surrounding medium just offshore down to the east normal faults penetrate through the upper crust the deeper crustal structure beneath appears upwarped from the basin towards etna juxtaposed with the crust of sicily a thinner crust reaches from the ionian basin under etna and the mantle is upwarped in such a structure magma can then be viewed as a melted lens capping a mantle upwarp at shallow depth rather than in an intracrustal chamber this reduces the conflict between estimates of its volume from excess output of volatiles and short residence times a link in time is indicated between volcanic and seismic activity at a large scale over the millennium the reported ends of episodes of high output rates of magma are followed by the reported occurrences of magnitude 7 earthquakes which caused destruction in southeastern sicily several steep active normal fault have been imaged to a depth of 10 km the crust up to 30 km offshore of the cities of catania and augusta which may be fault planes for such large earthquakes they expand and prolongate the system of the timpe faults on the eastern flank of etna thus linking large scale tectonics offshore with the volcano etna developed together with normal faulting upwarp and spreading during the recent evolution of the former ionian subduction activation of the material at depth at the lateral edge of the slab by vertical motion with extension above could produce the peculiar type of etna magmatism

feeding system and magma storage beneath mt etna as revealed by recent inflation deflation cycles 1 ground deformation at mt etna detected by three gps surveys carried out in 2004 2005 and 2006 is analyzed the data set encompasses the 2004 2005 eruptions and foreruns those of 2006 a wide deflation of the entire volcano was detected from 2004 to 2005 accompanying the 2004 2005 eruption conversely an evident inflation phase from 2005 to 2006 followed this eruption and preceded the 2006 one in both cases the deflation inflation cycle was accompanied by a continuous seaward motion of the eastern flank we inverted both data sets 2004 2005 deflation and 2005 2006 inflation using an optimization algorithm based on the genetic algorithm ga in order to detect the ground deformation sources the wide contraction measured during the eruption reveals the drainage of a sill shaped magma reservoir located by data inversions at a depth of about 4 5 km b s l the pressurizing source modeled for the 2005 2006 time interval indicates a refilling of the shallower near vertical plumbing system of the volcano this could indicate a change in the geometry of the feeding system active after the 2004 2005 eruption with a new and shallower magma storage that could have enabled the resumption of volcanic activity that was observed at summit craters in 2006 these results improve the imaging of the plumbing system of mt etna volcano

manganese deposits in the global lithogenetic system quantitative approach abstract a computerized data base including 330 localities and believed to represent at least 95 of the presently recorded spot accumulations of ore grade mn on land is the basis for a quantitative analysis of terrestrial mn resources this file is reprinted in full appendix the present subaerially exposed global ore mn resources are calculated as 17 9 109 t mn 1 in this figure are included the actually mineable straight mn deposits 8 7 109 t mn potentially mineable land based mn accumulations 9 2 109 t mn and actual or potential mn that could be extracted as a byproduct of mining other metals 0 6 109 t mn this distribution is strongly influenced by giant accumulations where the single exceptional kalahari mn field contains over 50 of the presently economic mn ore reserves or 23 42 of the global land mn resources a set of attributes has been selected to treat the global ore mn population in terms of genesis geotectonic and environmental setting and lithologic associations in terms of genesis precipitation from aqueous solutions was responsible for at least 99 of the contemporaneous and probably also the past mn accumulations now exposed on land weathering of mn orebodies has left its mark on 93 of the mn localities and 24 are now represented entirely by supergene assemblages less than 0 01 of the ore mn resources however are formed by weathering related accumulation over silicate rocks ultramafics in terms of geotectonic environments the bulk of the land based mn deposits 97 formed in intraplate and stable continental margin settings 3 1 formed along pacific type and rift type continental margins and only 0 00045 of the deposits formed in an oceanic setting this is in contrast with the outstanding mn accumulating capacity of the present ocean and is a consequence of the low preservation potential of the oceanic domain in terms of lithologic associations 96 of the mn in land based deposits is present in marine sedimentary associations 70 of mn is in banded iron formations 14 4 is in detrital and 11 1 is in carbonate dominated associations chert and jasper limestone sandstone shale and banded iron formation are statistically the most common immediate hosts to mn ores with recorded hosting frequencies of 79 50 45 37 and 35 respectively in terms of geological history the lower proterozoic accounts for 58 9 of the prreserved ore mn on land followed by oligocene 17 2 jurassic 6 2 and middle proterozoic 4 5 in terms of the intensity of mn accumulation per one million years of geological time oligocene 110 106 t mn ma is two orders of magnitude greater than the nearest time periods jurassic 8 9 106 t mn ma and lower proterozoic 6 5 106 t mn ma the historical distribution pattern of the land based mn deposits seems to indicate that accumulation of the bulk of the present ore grade mn is the result of repeated recycling with a land ocean trend abruptly initiated at the time of early cratonization about 2 5 ga this has been supplemented by a substantially less significant but remarkably steady reverse trend of addition of juvenile mn released from the mantle into the crust mafics and particularly basalts are the most important intermediaries in the cumulative secular increase of liberated and accumulated mn in the crust direct to indirect proven to hypothetical spatial coincidence of basalts and mn ores can be demonstrated on at least 169 localities out of 330 51 evaluated

geochemical constraints on the genesis of the montana de manganeso vein type mn deposit mexican plateau abstract manganese mineralization at montana de manganeso san luis potosi state consists of oxide ores that form sharp contacts with volcanic host rocks the orebodies are generally in the form of veins and irregular masses and locally as mineralized breccias petrographic analyses indicate that the mineralization is multi episodic with colloform and crustiform textures predominating the x ray diffraction and electron microscopy show that manganese oxides todorokite birnessite pyrolusite romanechite and cryptomelane are the main ore minerals while iron oxides goethite and hematite are accessory the most common gangue minerals are calcite and quartz with subordinate amounts of barite according to fluid inclusion microthermometry the mineralization is associated with aqueous solutions of intermediate salinity 8 to 16 wt nacl equivalent and temperatures between 101 and 140 c stable isotope analysis of calcite 13cpdb 7 76 to 6 32 18opdb 8 01 to 4 71 and barite 34s 7 9 to 13 6 shows a contribution of magmatic volatiles to hydrothermal fluids dominated by meteoric water calculated 18ofluid 6 58 to 13 14 relative to smow argillic alteration is the most widespread hydrothermal alteration at montana de manganeso and indicates fluid temperature below 150 c and near neutral ph much more local advanced argillic alteration revealed by the occurrence of kaolinite is interpreted as a steam heated overprint which in turn suggests a boiling process that must have happened at greater depths the mn ores formed through a process of mixing of a boiled off hydrothermal fluids with b cold diluted meteoric water our results support a hot spring deposit model according to which montana de manganeso corresponds to the shallowest portion of an epithermal system formed in a continental volcanic arc setting

deformation and eruptions at mt etna italy a lesson from 15 years of observations this work was partly funded by ingv and the italian dpc and was supported by asi the preview project and crdc amra dpc ingv flank project providing the funds for the publication fees

origin of manganese giants sea level change and anoxic oxic history inversely graded pisolites of manganese oxide in the mid cretaceous manganese giant at groote eylandt australia were deposited during a regional fall in sea level as indicated by their relationships to wave cut benches dissolved manganese was concentrated in relatively anoxic waters of the intracratonic basin during a marine transgression and precipitated as oxides and carbonates during a regression ore bodies ultimately formed by concentration of abundant particulate manganese by a tidal lag mechanism

a multidisciplinary study of the volcanoclastic deposit named chiancone inland and offshore in the frame of the evolution of volcanism in the etna area abstract in this work a detailed study about the volcanoclastic deposit pyroclastic cone called chiancone is carried out by 98 vertical electrical soundings vess and by analysis of the surface morphology made by two digital elevation model dem with high resolution the results seem to confirm what has been suggested by other researchers and shed some light on some dark aspects of this volcanoclastic deposit in particular it was found that the chiancone is quite a complex geologic formation whose deposition took place in several steps filling in depressions of various conductive substrate to depths of at least 300 m below the sea level the conductive substrate generally shows a higher resistivity than a clay one and is strongly tectonized and eroded the multibeam surveys carried out offshore in the ionian sea allow us to identify the geolithological nature of the substrate never before detected in the past they show the existence of an outcrop of a large cone shaped submarine pyroclastic body about 600 m deep covered near the coast by chiancone deposits the authors believe therefore that this pyroclastic body may form inland the conductive substrate of the formations outcropping in the studied area lava and chiancone and representing the product of the demolition of one or more existing volcanic apparatuses prior to the trifoglietto and mongibello which was given in the past the name of ancient etna

malta escarpment fault zone offshore eastern sicily pliocene quaternary tectonic evolution based on new multichannel seismic data 1 the malta escarpment represents the dominant morphological feature offshore eastern sicily linking the deep ionian basin to the east with the hyblean carbonate platform to the west interpretation of purposely acquired multichannel seismic data allows division of the malta escarpment into two portions characterized by different tectonic structures along the segment south of siracusa the malta escarpment is not affected by recent faulting and appears as a steep surface that flattens out toward the ionian basin a recent deformation characterized by a broad area of uplift occurs 20 30 km east from the slope along a nnw sse trend the segment of the malta escarpment extending north of siracusa on the other hand is characterized by the presence of nnw sse east dipping recent extensional faults and related sedimentary basins the observed structural features support the occurrence of a lithospheric tear between the ionian oceanic basin and the hyblean plateau

relevance of the chiancone volcaniclastic deposit in the recent history of etna volcano italy abstract the chiancone ch deposit is a volcaniclastic fan on the eastern flank of mt etna it crops out from the exit of the depression of the valle del bove 350 m a s l to the sea in an area which covers about 40 km 2 with a maximum thickness of about 30 m and a slope of 3 4 towards the east the total volume of the deposit is unknown because the base does not crop out but some geophysical data suggest a maximum thickness of about 300 m leading to an estimated maximum volume of about 12 km 3 which is comparable to the volume of the valle del bove vdb since this horseshoe shaped valley is considered to be the ch s source region a study of this deposit may allow an understanding of the mechanisms responsible for the origin of the vdb on the basis of stratigraphic and sedimentary studies we divided the ch sequence into two main parts the basal portion lithofacies 1 is visible only along the coast and has a width of about 6 5 km a thickness of 1 4 m and appears as an indurated horizontal deposit with a flat locally eroded upper surface we consider lithofacies 1 as a huge mud flow which may be associated with an important eruptive event the upper part lithofacies 2 5 is mainly composed of fluvial beds 63 of measured thicknesses that we attribute to events reworking the previously deposited layers the less abundant 23 very coarse grained lenses were caused by fluvial floods thin and discontinuous pyroclastic layers are accidentally 3 interbedded into the sequence the upper portion of the ch sequence is up to 30 m thick and formed after 7590 130 yr b p as established by our new radiocarbon dating when the chemical data obtained on lava blocks sampled from lithofacies 1 4 are compared with products of older eruptive centres it may be argued that the major direction of transport occurred from west to east and involved erosion of those old eruptive centres which were located in the central northern part of the vdb our data suggest the occurrence of an important eruptive event at least 7590 yr b p which may be associated with the deposition of the huge basal mud flow this event was followed by fluvial reworking and deposition at a rate of at least 4 mm yr extending this deposition rate to the whole thickness of the ch deposit 300 m would imply a maximum age of 80 000 70 000 yr b p however the deposition rate of the hidden part of the ch deposit was almost certainly much greater than 4 mm yr implying an age for the onset of the ch sequence significantly less than 80 000 70 000 yr b p this very strongly suggests that the trifoglietto volcano which is older than 80 000 yr was not involved in the opening of the vdb and the formation of the ch deposit it also suggests that the first event of the opening of the vdb was much older than the 5000 yr proposed by some authors it is possible that the ch was deposited during or slightly later than the life span of the ellittico volcano 40 000 15 000 yr b p

active spreading and regional extension at mount etna imaged by sar interferometry abstract large flank instability has been proposed by most recent authors as a major process in the dynamics of mount etna however several aspects of the models are still disputed such as the boundaries of the moving area and the driving force for the instability in this paper we present synthetic aperture radar interferometric data which allow us to identify two main sectors of active instability where the deformational process differs an eastern sector is bounded to the north by the pernicana provenzana fault to the west by the north rift zone and the south rift zone and to the south by the mascalucia tremestieri trecastagni fault system interferograms provide new data on the activity and extent of the southern boundary which was previously underestimated in this sector the structural features indicate an eastward sliding driven by e w regional extension which can be interpreted as a result of the retreating slab of the ionian subduction a second collapsing sector exists along the southern flank of mount etna where the interferograms show the presence of an active anticlinal ridge this ridge is interpreted as the result of southward gravity spreading over a basal decollement between etna and its plio quaternary basement and the hyblean platform the two sectors first became active in summer 1996 after the beginning of a new cycle of eruptive activity at the summit the activity was ongoing until january 1998 with the deformation rate ranging from 4 6 mm yr for the mascalucia tremestieri trecastagni faults to 12 mm yr for the anticlinal ridge

new results of 40ar 39ar dating constrain the timing of transition from fissure type to central volcanism at mount etna italy recent geological studies performed at etna allow reassessing the stratigraphic frame of the volcano where distinct evolutionary phases are defined this stratigraphic reconstruction was chronologically constrained on the basis of a limited number of u th and k ar age determinations whose uncertainty margins are sometimes too wide for this reason we successfully adopted at etna the 40ar 39ar technique that allowed obtaining more precise age determinations the incremental heating technique also gives information on sample homogeneity and potential problems of trapped argon five samples were collected from stratigraphically well controlled volcanic units in order to chronologically define the transition between the fissure type volcanism of the timpe phase to the central volcanism of the valle del bove centers isotopic ages with an uncertainty margin of 2 4 have been obtained emphasizing that this transition occurred 130 126 ka without significant temporal hiatus

dynamic deformation of etna volcano observed by satellite radar interferometry satellite radar interferometry of mt etna volcano sicily italy reveals a sequence of deformation characterized by deflation during the end of the 1993 eruption inflation from 1993 1995 with an increase in the inflation rate immediately before its resumed eruptive activity in late 1995 this was followed by very low deformation levels during the following year the source of the deformation changed from a depth of 9 km during deflation to more than 11 14 km during the subsequent inflation consistent with a model in which deflation at shallower levels is followed by inflation at greater depth as the volcano system recharges from below before its next eruption this study demonstrates that radar interferometry provides an important contribution towards understanding the dynamic deformation of volcanoes by revealing large scale changes in their pre eruption deformation rates radar interferometry could play an important role in volcano eruption monitoring

paleo environmental and volcano tectonic evolution of the southeastern flank of mt etna during the last 225 ka inferred from the volcanic succession of the timpe acireale sicily abstract the tectonic escarpments locally known as timpe cut a large sector of the eastern flank of etna and allow an ancient volcanic succession dating back to 225 ka to be exposed geological and volcanological investigations carried out on this succession have allowed us to recognize relevant angular unconformities and volcanic features which are the remnants of eruptive fissures as well as important changes in the nature composition and magmatic affinity of the exposed volcanics in particular the recognition in the lower part of the succession of important and unequivocal evidence of ancient eruptive fissures led us to propose a local origin for these volcanics and to revise previous interpretations which attributed their westward dipping to the progressive tectonic tilting of strata these elements led us to reinterpret the main features of the volcanic activity occurring since 250 ka bp and their relationship with tectonic structures active in the eastern flank of etna we propose a complex paleo environmental and volcano tectonic evolution of the southeastern flank of mt etna in which the timpe fault system played the role of the crustal structure that allowed the rise and eruption of magmas in the above considered time span

spatial variations of seismogenic stress orientations in sicily south italy abstract seismogenic stress orientations are estimated in the lithosphere of sicily by inversion of 131 local earthquake focal mechanisms fms selected from the literature an average misfit f 14 5 between stress tensor and fms indicates that the entire set of earthquakes is generated by a highly heterogeneous stress field detailed analysis of stress tensors and related earthquake misfits obtained for tens of subsets based on spatial separation of data allowed us to identify two main stress domains in the study region i a compressional domain including etna western sicily and the southern tyrrhenian sea offshore sicily where the 1 orientation roughly changes from nw se in the etna area and western sicily to nne ssw at the northeastern edge of the domain eolian islands and ii an extensional domain in northeastern sicily between the eolian islands and etna where 3 is oriented analogously to previously estimated in the easterly confining extensional area of the messina straits general agreement is found between this stress pattern and the gps crustal displacement vectors reported in the most recent literature for the study region moreover stress inversion enables us to locate the extensional domain more accurately than the presently available gps data finally the stress orientations estimated in the southern and western sectors of the study area etna and western sicily on and offshore match well with the displacement fields predicted for sicily by large scale models of plate motion conversely a mismatch is observed in the northeastern sector eolian islands and northeastern sicily we suggest that the joint action of africa eurasia convergence and ionian subduction trench retreat rollback of the subducting slab may explain the stress pattern detected in sicily in the present study work for computation of a finite element regional geodynamic model based on geophysical and geological data collected over the last few years has recently started with the purpose of quantitatively checking this hypothesis

structural features of an active strike slip fault on the sliding flank of mt etna italy abstract the strike slip pernicana fault system pfs was activated along the eastern flank of mt etna during an earthquake in september 2002 and one month later during the eruption of the ne rift structural and volcanological data suggest that the pfs was activated as a result of the slide of the ne flank of etna this activation produced surface fracturing on walls and on paved and unpaved roads the segments of the pfs arranged in a right stepping en echelon configuration show a an inverse proportion between length and frequency b fractal behavior over scales of 10 2 10 1 m between their length overstep and overlap c consistent strike with regard to their fault array and d a progressive eastward decrease in the displacement along the smallest faults the consistent geometric and kinematic features of the pfs related to the sector collapse of etna are similar to those of faults in strike slip settings

crustal structure of the ionian margin of sicily etna volcano in the frame of regional evolution abstract crustal imaging could be achieved on normal incidence reflection profiles offshore eastern sicily by using industrial grade reflection seismic with improved marine sources thick recent sediments a reflective pile including the mesozoic deposits a transparent upper crust and a band of low frequency reflections attributed to the lower crust are imaged in the seismic sections the structure of the crust and its thickness show features inherited from the mesozoic evolution as a passive margin by which ionian basin crust was formed around the hyblean continental promontory of africa to constitute the southern plate in the later convergence with europe the seismic images are also marked by the lithospheric deformation due to the neogene overriding of the northern part of this paleomargin by the calabro peloritan block of european continental crust this transpressive motion may have been guided along the northern part of this paleomargin where the seismic profiles evidence a hinge line between the northward upslope of the moho of that old passive margin and its downslope to the present slab under the tyrrhenian sea etna volcano is located at the intersection of this mantle upwarp by a zone of active sea bottom normal faults which cut across the formerly constructed compressional belt the onset of its volcanic activity is roughly coeval with that of the cessation of interplate thrusting and could hence be related to a change of the coupling of the ionian slab this slab is now probably disconnected from the overriding plate and rolled back in front of the expanding hot tyrrhenian asthenospheric dome with the mobilisation of a viscous mantle material at depth an active lithospheric fault is here imaged which cuts over more than 100 km into the ionian basin the fault runs from the tyrrhenian margin in the sse direction of etna updip of the southwestern lateral edge of this slab leaving north eastward the extruded calabrian block and on its south westward edge the uplifted crust and mantle structures of etna along it the crust including the mesozoic and deeper layers has sagged vertically in the segment in front of the slab with a finite throw across the fault increasing from the basin towards etna

evolution of the southern tyrrhenian slab tear and active tectonics along the western edge of the tyrrhenian subducted slab abstract the evolution of the southern tyrrhenian subduction has been possibly controlled by distinct episodes of slab break off as indicated by a critical review of the geological literature and by the analysis of purposely acquired multichannel seismic profiles within the proposed interpretation the first episode occurred from 8 5 to 4 0 ma and affected the segment of the slab located in the sardinia channel causing the abandonment of the adventure thrust front in western sicily the second episode occurred between 2 5 and 1 6 ma affecting the segment of slab located north of sicily and was preceeded by rifting in the strait of sicily the space and time location of these episodes appear controlled by discontinuities pre existing within the subducted african plate that trend at high angle to the advancing subduction front these discontinuities delimit segment of subducted slab that can be affected by slab break off and can act as wayouts for magma and mantle derived he the major of these discontinuities the malta escarpment has been reactivated in the quaternary as a trench perpendicular tear step faults ultimately the hierarchy in strength of these trench perpendicular features could have affected the timing and amount of trench retreat and backarc opening

the role of the pernicana fault system in the spreading of mt etna italy during the 2002 2003 eruption flank instability and collapse are observed at many volcanoes among these mt etna is characterized by the spreading of its eastern and southern flanks the eastern spreading area is bordered to the north by the e w trending pernicana fault system pfs during the 2002 2003 etna eruption ground fracturing along the pfs migrated eastward from the ne rift to as far as the 18 km distant coastline the deformation consisted of dextral en echelon segments with sinistral and normal kinematics both of these components of displacement were one order of magnitude larger 1 m in the western previously known portion of the pfs with respect to the newly surveyed 9 km long eastern section 0 1 m this eastern section is located along a pre existing but previously unknown fault where displaced man made structures give overall slip rates 1 1 9 cm year only slightly lower than those calculated for the western portion 1 4 2 3 cm year after an initial rapid motion during the first days of the 2002 2003 eruption movement of the western portion of the pfs decreased dramatically while parts of the eastern portion continued to move these data suggest a model of spreading of the eastern flank of etna along the pfs characterized by eruptions along the ne rift instantaneous short lived meter scale displacements along the western pfs and more long lived centimeter scale displacements along the eastern pfs the surface deformation then migrated southwards reactivating one after the other the nnw sse trending timpe and trecastagni faults with displacements of 0 1 and 0 04 m respectively these structures along with the pfs mark the boundaries of two adjacent blocks moving at different times and rates the new extent of the pfs and previous activity over its full length indicate that the sliding eastern flank extends well below the ionian sea the clustering of seismic activity above 4 km b s l during the eruption suggests a deep decollement for the moving mass the collected data thus suggests a significant movement volume 1 100 km3 of the eastern flank of etna both on shore and off shore

fe isotopes of a 2 4 ga hematite rich if constrain marine redox conditions around the goe abstract the hematite and manganese rich hotazel iron formation griqualand west basin south africa was deposited at a key moment in time close to the goe between 2 4 and 2 3 ga it stratigraphically overlies the ongeluk formation comprising thick flood basalts which in turn interfinger with and cover the makganyene formation diamictites the inferred remnants of the first paleoproterozoic snowball earth interval no extensive research has been conducted to date on the basal part of the hotazel formation due to poor exposure though it constitutes an important link between a period of large scale ice cover extensive volcanism and the onset of atmospheric oxygenation here we present a detailed petrographic geochemical and fe isotope study of a roughly 3 metre long drill core exposing the ongeluk to hotazel contact our results show that after the cessation of ongeluk volcanism primary precipitation of fe iii oxyhydroxides from the photic surface zone of the original basin became the dominant sedimentation mechanism negative 56fe values between 0 26 and 0 50 in micro drilled hematite rich chert indicate that surface water 56fe compositions at the time of deposition were depleted yet 56fe and bulk rock fe mn values are still substantially higher 1 2 than those reported higher up in the mn rich layers of the hotazel sequence suggesting that redox potentials were still comparatively limited during the earliest stages of the hotazel depositional environment the base of the hotazel formation thus forms a transitional interval between precipitation from essentially ferruginous seawater as recorded in the ghaap group bifs and from isotopically and chemically highly evolved surface waters as demonstrated by the hotazel mn rich layers in the absence of fe ii as a strong reducing agent large volumes of photosynthetic oxygen may have eventually escaped into the atmosphere leading to the onset of atmospheric oxygenation our results thus contradict previous models that place the onset of the goe before the hotazel formation concurrent with and mechanistically linked to the makganyene and ongeluk events instead we show that the hotazel basal sediments are still pre goe consistent with their circa 2 4 ga age and the continuation of mif s higher in the stratigraphic record

sedimentary manganese metallogenesis in response to the evolution of the earth system abstract the concentration of manganese in solution and its precipitation in inorganic systems are primarily redox controlled guided by several earth processes most of which were tectonically induced the early archean atmosphere hydrosphere system was extremely o2 deficient thus the very high mantle heat flux producing superplumes severe outgassing and high temperature hydrothermal activity introduced substantial mn2 in anoxic oceans but prevented its precipitation during the late archean centered at ca 2 75 ga the introduction of photosystem ii and decrease of the oxygen sinks led to a limited buildup of surface o2 content locally initiating modest deposition of manganese in shallow basin margin oxygenated niches e g deposits in india and brazil rapid burial of organic matter decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the archean proterozoic transition concurrently a massive drawdown of atmospheric co2 owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused paleoproterozoic glaciations 2 45 2 22 ga the spectacular sedimentary manganese deposits at ca 2 4 ga of transvaal supergroup south africa were formed by oxidation of hydrothermally derived mn2 transferred from a stratified ocean to the continental shelf by transgression episodes of increased burial rate of organic matter during ca 2 4 and 2 06 ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere black shale hosted mn carbonate deposits in the birimian sequence ca 2 3 2 0 ga west africa its equivalents in south america and those in the francevillian sequence ca 2 2 2 1 ga gabon are correlatable to this period tectonically forced doming up attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric co2 drawdown causing glaciation on the neoproterozoic rodinia supercontinent tectonic rifting and mantle outgassing led to deglaciation dissolved mn2 and fe2 concentrated earlier in highly saline stagnant seawater below the ice cover were exported to shallow shelves by transgression during deglaciation during the sturtian glacial interglacial event ca 750 700 ma interstratified mn oxide and bif deposits of damara sequence namibia was formed the varangian marinoan ca 600 ma cryogenic event produced mn oxide and bif deposits at urucum jacadigo group brazil the datangpo interglacial sequence south china liantuo nantuo varangian event contains black shale hosted mn carbonate deposits the early paleozoic witnessed several glacioeustatic sea level changes producing small mn carbonate deposits of tiantaishan early cambrian and taojiang mid ordovician in black shale sequences china and the major mn oxide carbonate deposits of karadzhal type central kazakhstan late devonian the mesozoic period of intense plate movements and volcanism produced greenhouse climate and stratified oceans during the early jurassic oae organic rich sediments host many mn carbonate deposits in europe e g urkut hungary in black shale sequences the late jurassic giant mn carbonate deposit at molango mexico was also genetically related to sea level change mn carbonates were always derived from mn oxyhydroxides during early diagenesis large mn oxide deposits of cretaceous age at groote eylandt australia and imini tasdremt morocco were also formed during transgression regression in greenhouse climate the early oligocene giant mn oxide carbonate deposit of chiatura georgia and nikopol ukraine were developed in a similar situation thereafter manganese sedimentation was entirely shifted to the deep seafloor and since ca 15 ma b p was climatically controlled glaciation deglaciation assisted by oxygenated polar bottom currents aabw nadw the changes in climate and the sea level were mainly tectonically forced

gravity and magma induced spreading of mount etna volcano revealed by satellite radar interferometry 1 mount etna underwent a cycle of eruptive activity over the past ten years here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal mount etna s average and time varying surface deformation from 1992 to 2001 we find that during this time interval it experienced magmatic inflation and radial spreading to the west south and east steady relative motion between the west and south flanks and between the east and north flanks during this time interval suggests they are related to gravitational spreading of the volcanic edifice time series analysis shows that growth of a southeastern basal anticline began with the end of magma recharge in 1995 thus showing a direct link between deep seated magma intrusions and edifice spreading these observations support a complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading although ultimately the two must be related

actively growing anticlines beneath catania from the distal motion of mount etna s decollement measured by sar interferometry and gps we used sar interferometry and gps to measure the rise of an anticline beneath the urban area of catania italy which originates from outward thrusting above the basal decollement of etna volcano the anticline grows at a rate of over 0 015 m a 1 of se thrusting and about 0 007 m a 1 of relative uplift by relating this growth to the simultaneous extension measured at the summit of the volcano we demonstrate the occurrence of active volcanic spreading this process may exert a control on eruptions earthquakes sector collapses and landslides

dynamics of mount etna volcano inferred from static and kinematic gps measurements 1 ground deformations measured on mount etna from late 1995 to mid 1998 using gps observations are analyzed four gps surveys were carried out during the considered period in 1995 the gps network consisted of 18 stations on the volcanic edifice and 6 stations around it during the 1996 survey 22 new monuments were added along a n s profile crossing the summit craters area this profile was surveyed by a semikinematic method allowing greater spatial detail to be achieved on the uppermost part of the volcano the comparisons between the gps surveys are reported here in terms of horizontal and vertical displacements for each station and also in terms of areal dilatation and strain distribution this last parameter continues its ascending trend at a rate of 5 strain yr 1 already shown in the previous period after the end of the 1991 1993 flank eruption inversion of the ground deformation patterns permits investigation of the evolution of both the position and dynamics of magma reservoirs beneath the volcano consistently associated with a general eastward sliding of its eastern sector this study allows us to define the nonuniqueness of ground deformation sources through the investigated period suggesting that the plumbing system of the volcano is made up of a complex system of single intrusions occurring at different times

magma ascent and the pressurization of mount etna s volcanic system after a period of deflation during the 1991 1993 flank eruption mount etna underwent a rapid inflation seismicity and ground deformation show that since 1994 a huge volume of magma intruded beneath the volcano producing from 1998 onward a series of eruptions at the summit and on the flank of the volcano the last of these started on 27 october 2002 is still in progress and can be considered one of the most explosive eruptions of the volcano in recent times here we show how geodetic data and seismic deformation between 1994 and 2001 indicate a radial compression around an axial intrusion consistent with a repressurization of mount etna s plumbing system at a depth of 6 to 15 kilometers which triggered most of the seismicity and provoked the dilatation of the volcano and the recent explosive eruptive activity

control of rock rheology on deformation style and slip rate along the active pernicana fault mt etna italy abstract the already known part of the active left lateral strike slip pernicana fault on the eastern flank of mt etna volcano has a holocene high slip rate of 1 5 2 7 cm yr but its surface trace abruptly disappears eastward approaching the lower slope of the volcano using geological geomorphological and structural surveys we found that the pernicana deformation zone extends 8 km further to the east beyond this point through a different mechanism as the thickness of the volcanic pile decreases the single e w to ese striking main fault plane gives way to a set of faults arranged in a splay structure which partitions the fault motion here slip rates are 0 4 to 1 4 cm yr on each fault further east where the lava succession is very thin and unfaulted we suggest that lavas are decoupled from plastic deforming sub etnean clay deposits which absorb the strain or that lavas have a too low mass to slide on the very lowest slope of the volcano i e further east lavas are once again thicker and the pernicana deformation zone behaves at the surface once again in a brittle manner locally known as the fiumefreddo fault with a low slip rate of

a ground water mixing model for the origin of the imini manganese deposit cretaceous of morocco the imini deposit just south of the atlas mountains of morocco consists of three beds of manganese oxide ore in a slightly deformed dolomite unit about 10 m thick of cenomanian turonian late cretaceous age the dolomite host is sugary textured massive and permeable dolomite occurs as nearly euhedral rhombs each ore bed is about a meter thick and consists almost entirely of intergrowths of pyrolusite and hollandite family minerals bao up to 11 and pbo up to 28 with a flattened geode structure overlying the ore beds are solution collapse breccias with dolomite clasts janggunite mn fe oxide and dolomite matrix and pyrolusite hollandite calcite cement the ore solution collapse breccia and coarsely recrystallized pure dolomite are coextensive a zone only 400 to 1 000 m wide but 25 km long and elongate east northeast west southwest diagenetic features of the deposit are recrystallized texture of the dolomite flattened geode structure of the ore solution collapse breccia and associated draped laminae of the insoluble residues fossil replacement by mn oxides and zoned chert nodules with inclusions a mineralogic paragenesis shown independently in each of these features from older to younger is 1 precursor carbonates 2 dolomite janggunite and 3 hollandite pyrolusite chert calcite diagenesis probably occurred during the late cretaceous in a mixing zone of fresh and saline ground water as similar diagenetic sequences without manganese deposits are widely reported to have formed in such environments carbon and oxygen isotope compositions of carbonates and oxygen isotope compositions of chert show that an increasing component of fresh meteoric ground water was present as diagenesis proceeded falling sea level allowed the mixing zone to occupy various positions within the carbonate unit and convert the primary calcareous carbonate rocks to dolomite with chert nodules anoxic seawater is known both worldwide and from the local depositional basin atlas gulf in the cenomanian turonian this is believed to be the key to manganese deposition because anoxic conditions greatly enhance manganese solubility two specific versions of the mixing zone model are presented for manganese deposition one in which a primary sedimentary manganese precipitate formed along margins of the anoxic basin and was recrystallized during diagenesis in the mixing zone and the other in which anoxic saline ground water brought manganese into the mixing zone where it precipitated

debris avalanche deposits of the milo lahar sequence and the opening of the valle del bove on etna volcano italy previously undescribed debris avalanche deposits occur in two locations downslope from the open end of the valle del bove these outcrops comprise unstratified ungraded deposits of metre scale lava blocks in a matrix of weathered and fractured lava clasts the avalanche deposits are unconformably overlain by matrix to clast supported conglomerates representing debris flow and interbedded fluvial deposits that constitute most of the milo lahar sequence we present evidence that the milo lahar sequence which crops out just at the exit of the valle del bove formed during the opening and enlargement of this depression the presence of the avalanche deposits at the base of the milo lahar sequence indicates that catastrophic landslides were involved in the formation of the valle del bove the composition of lavas in the debris avalanche deposits is similar to that of most of the ellittico volcanic sequence exposed along the northern wall of the valle del bove radiocarbon dates of 8400 and 5300 years bp from the base and top respectively of the debris flow sequence indicate that the milo lahars are correlative with the exposed part of the chiancone deposit the basal lahars of the chiancone which contain lava blocks whose compositions partially overlap that of blocks in the avalanche deposits may have formed by water concentration in the distal end of the avalanche causing transformation to debris or alternatively by reworking of the avalanche deposit

geological and geomorphological evolution of the etna volcano ne flank and relationships between lava flow invasions and erosional processes in the alcantara valley italy abstract in this paper the interrelationships between volcanic activity and fluvial events in the alcantara valley are investigated based on the correlation between the stratigraphy of the ne flank of mt etna and subsurface data the geological and geomorphological evolutions of the valley are reconstructed new 1 10 000 scale geological mapping shows that the bulk of this sector of the volcano is made up of the ellittico volcano lava flows though they are widely covered by the products of the eruptive activity of the last 15 ka the present day morphological setting of the alcantara valley is the result of two main evolutionary phases initiated during the activity of the ellittico volcano only one lava flow invasion of the valley floor occurred in the first phase this phenomenon was followed by a long period of erosional processes leading to the entrenchment of the drainage pattern and the erosion of the ellittico lava flow about 20 25 ka ago an important change in the frequency of the lava flow invasions into the valley occurred associated with the final stage of the ellittico volcano activity marking the beginning of the second phase during this phase volcanic processes became predominant with respect to other morphogenetic processes in the alcantara valley lava flows coming from the ne flank of the ellittico volcano caused a radical modification of the morphological setting of this area even though only one lava flow emitted by an eruptive fissure located within the valley partially filled the riverbed during the eruptive activity of the last 15 ka the complete filling of the alcantara valley floor occurred in particular between 15 and 7 ka a lava flow originated from the mt moio scoria cone filled the valley floor for a distance of about 9 km following a short period of erosion an eruptive fissure located within the valley generated a 20 21 km long lava flow that was channelled along the full extent of the alcantara valley and stretches for about 3 km offshore in the ionian sea in the last 7 ka lava flows originating from the ne rift zone produced only temporary damming of the riverbed without any important contribution to the filling of the alcantara valley

manganese mineralization in archean greenstone belt joda noamundi sector noamundi basin east indian shield abstract a mesoarchean greenstone belt 3 5 3 0 ga in the western part of the east indian shield comprising the iron ore group of the noamundi basin contains economic resources of both iron and manganese ores in the nne plunging regional synclinorium manganese mineralization in the central and eastern parts of this synclinorium particularly in joda noamundi sector has taken place in multiple cycles starting from syngenetic sedimentary and exhalative type through mobilization and remobilization in different stages of tectonism deformation and hydrothermal activities to latest lateritic or supergene type a relatively high temperature metamorphic jacobsite hausmannite bixbyite braunite assemblage low temperature hydrothermal pyrolusite psilomelane hollandite assemblage and supergene pyrolusite manganomelane groutite polianite assemblage are present and were formed by recycling of manganese in different stages of mineralization a detailed structural study of the manganese ore bodies as well as their ore petrographic and mineralogical characteristics with mineral chemistry has revealed systematic mineralization and their relation to deformational phases such recycling of manganese and its structural control of mineralization in different phases is unique of its kind in comparison with other archean manganese deposits in the world

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

continental margin large scale instability controlling the flank sliding of etna volcano abstract etna volcano is affected by a downward sliding of its eastern flank as rapid as a few cm year whose nature is highly debated recently collected marine geological and geophysical data allows a detailed image of the morphostructural setting of the continental margin facing the volcano here a large bulge offsets the margin that is deeply affected by widespread semicircular steps interpreted as evidence of large scale gravitational instability such features permeate the whole margin and extend inshore to the volcano sector where the larger ground deformations are measured both submarine instability and subaerial flank sliding are bounded by two regional tectonic lineaments interpreted as weakness lines these cross the coastline to accommodate the basinward movement of this large sector of the continental margin topped by the etna volcanic pile the new data allows re interpreting the tectonic setting of the coastal belt and proposing a novel structural model highlighting the active role of the continental margin instability to drive the seaward sliding of the volcano s eastern flank this model may suggest why a very active basaltic volcano has so unusually developed in front of an active thrust belt

static stress changes induced by the magmatic intrusions during the 2002 2003 etna eruption 1 the shallow intrusive processes that occurred during 2002 2003 etna eruption as well as the complex interaction between the magma intrusive events and the tectonic response of the volcano s eastern flank are investigated with numerical deformation modeling and the estimation of changes in the static coulomb stress ground deformation and volcanologic evidence clearly indicate a composite mechanism of intrusion on both the southern and northeastern flanks of the volcano geodetic data inversions have been based on a homogeneous elastic half space model although geological data and seismic tomography indicate that mt etna is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of the deformation field to account for topographic effects as well as a complicated distribution of material properties we use the finite element method fem to provide a more realistic model the presence of medium heterogeneity strongly affects the amplitudes of the static stress changes seismicity matches well the areas of positive increase in the static stress caused by the intrusive events along the southern and northeastern flanks the changes in the state of stress generated by the southern dike produce an extensional stress field that favors magma propagation along the north east rift the highest seismic releases were associated with the activation of two fault systems the timpe fault system and the pernicana fault the static stress changes resolved onto these faults indicate that the magma intrusions on the southern and northeastern flanks encouraged these seismogenic structures to slip

anatomy of an unstable volcano from insar multiple processes affecting flank instability at mt etna 1994 2008 1 volcano deformation may occur under different conditions to understand how a volcano deforms as well as relations with magmatic activity we studied mt etna in detail using interferometric synthetic aperture radar insar data from 1994 to 2008 from 1994 to 2000 the volcano inflated with a linear behavior the inflation was accompanied by eastward and westward slip on the eastern and western flanks respectively the portions proximal to the summit showed higher inflation rates whereas the distal portions showed several sectors bounded by faults in some cases behaving as rigid blocks from 2000 to 2003 the deformation became nonlinear especially on the proximal eastern and western flanks showing marked eastward and westward displacements respectively this behavior resulted from the deformation induced by the emplacement of feeder dikes during the 2001 and 2002 2003 eruptions from 2003 to 2008 the deformation approached linearity again even though the overall pattern continued to be influenced by the emplacement of the dikes from 2001 to 2002 the eastward velocity on the eastern flank showed a marked asymmetry between the faster sectors to the north and those largely inactive to the south in addition from 1994 to 2008 part of the volcano base south west and north lower slopes experienced a consistent trend of uplift on the order of 0 5 cm yr this study reveals that the flanks of etna have undergone a complex instability resulting from three main processes in the long term 103 104 years the load of the volcano is responsible for the development of a peripheral bulge in the intermediate term 101 years observed from 1994 to 2000 inflation due to the accumulation of magma induces a moderate and linear uplift and outward slip of the flanks in the short term 1 year observed from 2001 to 2002 the emplacement of feeder dikes along the ne and south rifts results in a nonlinear focused and asymmetric deformation on the eastern and western flanks deformation due to flank instability is widespread at mt etna regardless of volcanic activity and remains by far the predominant type of deformation on the volcano

detachment depth revealed by rollover deformation an integrated approach at mount etna this work was partially funded by ingv and the dpc ingv project flank and partially by the asi srv project

nature and development of supergene manganese deposits groote eylandt northern territory australia abstract supergene manganese ores occur on groote eylandt in association with other secondary rocks overprinting primary sedimentation features e g oolitic and pisolitic units secondary mn oxides and gangue minerals nowadays belong to the most important components in the deposits the different primary and supergene rock types are described and discussed with the help of typical geological profiles in an idealized vertical cross section we present a combination of all observed supergene mn ores mangcretes many parts of this section can be encountered in various localities of the groote eylandt deposits the most common minerals found on the island are pyrolusite cryptomelane romanechite psilomelane todorokite quartz kaolinite goethite and hematite probably with the exception of todorokite all other mentioned phases can occur as primary and or supergene minerals the dominant process for the dissolution of mn oxides is a redox reaction between divalent iron and tetravalent manganese other leaching processes are of subordinate importance we discuss transport and precipitation which lead to the development of a mangcrete model for supergene mn deposits finally the supergene products are compared with secondary ores of other manganese deposits and it can be seen that in spite of different protores the supergene materials can be very similar in their physical appearance and mineralogy

hydrothermal manganese deposits in island arcs and related to subduction processes a possible model for genesis abstract submarine hydrothermal manganese deposits have recently been recovered from a number of island arc settings such as the tonga kermadec ridge ogasawa arc trench bonin arc mariana arc and bismarck archipelago it has also been shown that large volumes of fluid are released during dewatering of subducting sediments the amount of water subducted globally 1 5 10 15 g yr 1 is about two orders of magnitude less than that advected at ocean spreading centres hydrothermal manganese deposits may be precipitated from these waters the distribution of terrestrial manganese deposits around the circum pacific belt and elsewhere suggests that some of these deposits may be of hydrothermal origin related to subduction processes at present most of these terrestrial deposits are inadequately described to permit the establishment of the precise tectonic setting at the time of deposition of the manganese deposits and therefore an unambiguous assessment of this hypothesis