present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

regional scale co seismic landslide assessment using limit equilibrium analysis abstract traditionally regional assessment of seismic slope stability has been done using the infinite slope rigid sliding block analysis a major disadvantage of this approach is the resulting overestimation of the critical acceleration of the slope due to the underlying assumption of a predefined slope failure plane and consequently the underestimation of hazard areas prone to sliding in this paper we present a modified approach for assessing seismic slope instabilities using a model based on limit equilibrium analysis and circular slip surfaces with no restriction to any predefined slope failure plane for this purpose we conduct a parametric study to identify the relationship between the critical acceleration of the slope the slope angle and the slope shear strength parameters we model typical slopes in the rocscience software slide using bishop s limit equilibrium method to identify the critical accelerations that corresponds to a failure plane with factor of safety equal to one the critical accelerations were plotted against the variables in the parametric study and the best fit equations were obtained the proposed approach was developed for global application but it was tested using the well documented co seismic landslide database of the 1994 northridge ca earthquake the predicted sliding areas were compared to the inventory of landslides that were triggered in the val verde region in los angeles by the earthquake qualitative and quantitative assessments of the proposed model clearly show its advantages in predicting potential sliding areas

brazilian structural provinces an introduction abstract the territory of brazil coincides almost entirely with the south american platform the crystalline core of the continent its basement is composed of ancient metamorphic and igneous rocks and it has not suffered any tectonic regeneration since the beginning of the phanerozoic sedimentary rocks with almost horizontal bedding cover this crystalline basement this latter shows ages as old as early precambrian although ages between 500 and 1000 m y are conspicuously frequent the cratonic areas became consolidated more than 1700 m y ago whereas the fold belts formed essentially between 500 and 1700 m y ago the sedimentary cover accumulated from the early silurian in three large intracratonic basins until the platform became completely stabilized a late jurassic to early cretaceous reactivation caused by the break up of the ancient gondwana continent created another basin sequence chiefly along the atlantic continental margin based on the nature of the crystalline basement rocks and the sedimentary cover ten structural provinces can be distinguished 1 rio branco province in the north of the country occupied by the guyana shield and still only poorly known with an important fold belt developed during the so called transamazonian cycle 2000 200m y with high grade metamorphic rocks and only slight influence of later events 2 tapajos province in central brazil corresponding to the amazonas or guaporecraton showing chiefly precambrian crystalline rocks and behaving as an cratonic area during the phanerozoic 3 sa o francisco province located on the atlantic shield with its basement covered by rocks of different ages chiefly affected by the brasiliano cycle between 1000 and 500 m y and constituting another cratonic area 4 tocantins province between the amazonas and sa o francisco cratons with the oldest rocks in its centre ages over 2600 m y and at the eastern and western borders metamorphic sequences of various fold belts and almost no phanerozoic deposits 5 mantiqueira province located along the southern part of the atlantic coast affected chiefly by the brasiliano folding cycle 6 borborema province in the northeast brazilian fold belt affected by the brasiliano cycle in a very complex way and with important faulted zones it was reactivated in phanerozoic times when also sedimentary covers accumulated 7 amazonas province represented by the amazonas sedimentary basin syneclise and subdivided into four parts by three important arcs 8 parnaiba province coinciding with the piauf maranha o syneclise and filled with a rather thick sedimentary sequence 9 paranaprovince the sedimentary basin of southern brazil in which the well known late paleozoic glaciation features are found and which possesses an extensive cover of basaltic rocks of late jurassic to early cretaceous age 10 coastal province and continental margin the youngest structural unit developed during the separation of the continent and represented by rift valleys and coastal basins filled with mesozoic cenozoic deposits of various kinds

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

extraordinary distance limits of landslides triggered by the 2011 mineral virginia earthquake the 23 august 2011 mineral virginia earthquake m w 5 8 was the largest to strike the eastern u s since 1897 and was felt over an extraordinarily large area although no large landslides occurred the shaking did trigger many rock and soil falls from steep river banks and natural cliffs in the epicentral area and from steep road cuts along and northwest of the blue ridge parkway we mapped the occurrence of rock falls to determine distance limits that could be compared with those from other documented earthquakes studies of previous earthquakes indicated a maximum epicentral distance limit for landsliding of 60 km for an m 5 8 earthquake the maximum distance limit for the 2011 earthquake was 245 km the largest exceedance of the historical limit ever recorded likewise the previous maximum area affected by landslides for this magnitude was 1500 km2 the area affected by landslides in the 2011 earthquake was 33 400 km2 these observations provide physical evidence that attenuation of strong shaking for eastern u s earthquakes is significantly lower than for plate boundary earthquakes also distance limits parallel to the regional structural trend are greater than those that transect the structure which suggests anisotropic attenuation related to the regional geologic structure peak ground acceleration pga at the landslide distance limits is estimated to have been about 0 02 0 04 g

compositional variations of olivine from the jinchuan ni cu sulfide deposit western china implications for ore genesis the jinchuan ni cu sulfide deposit is hosted by an elongated olivine rich ultramafic body that is divided by subvertical strike slip faults into three segments central eastern and western the central segment is characterized by concentric enrichments of cumulus olivine crystals and interstitial sulfides pyrrhotite pentlandite chalcopyrite intergrowth whereas the eastern and western segments are characterized by an increase of sulfides toward the lower contacts in all segments sulfides are concentrated at the expense of intercumulus silicates olivine re crystallization is found to be associated with actinolite alteration in some samples the compositional variations of primary olivine from the sulfide poor samples can be explained by a small degree of olivine crystallization 50 modal and sulfide averaging 5 wt in the rocks are consistent with the interpretation that the jinchuan deposit was formed by olivine and sulfide laden magma successively ascending through a conduit to a higher now eroded level sulfide enrichment toward the center in the central segment and toward the lower contact in the eastern and western segments may have in part resulted from flow differentiation and gravitational settling during magma ascent respectively

back analysis of the joss bay chalk cliff failure using numerical modelling use of numerical modelling for back analysis of slope failure can provide a valuable insight into the underlying failure mechanisms and improve our understanding of factors controlling instability and geomorphology of slopes this paper provides a brief overview of the range of methods that are available for slope instability analyses and their respective benefits using the back analysis of the joss bay chalk cliff failure as a case example a variety of analytical and numerical approaches are used to back analyse the failure to assess the potential impact of both the rock mass strength and discontinuity controlled behaviour on the potential failure mechanism limit equilibrium analysis approaches are used to assess the sensitivity of the simulated model to variation in input parameters numerical simulation constrained by the limit equilibrium models is then used to evaluate the progressive nature of failure mechanism and directly simulate the trigger mechanism importantly the modelling demonstrates that shear strain initiates at the base of the cliff and subsequently extends upwards resulting in tensile failure in the upper part of the slope the case example demonstrates the capability of numerical models to simulate the progressive nature of slope failure and their ability to evaluate the detrimental effects of a wave cut notch at the base of a cliff

platinum group minerals in the limoeiro ni cu pge sulfide deposit brazil the effect of magmatic and upper amphibolite to granulite metamorphic processes on pgm formation the limoeiro ni cu platinum group elements pge deposit is a recent discovery associated with an igneous tubular conduit system in northeastern brazil representative ores from the deposit have been used for platinum group minerals pgm identification and for pge in base metal sulfides bms quantification ninety eighty percent of the pgm in the massive sulfide ores is homogeneous pt ni bi bearing merenskyite pdte2 enclosed primarily by pyrrhotite suggesting that it is formed by exsolution from monosulfide solid solution mss merenskyite gradually but systematically becomes poorer in pt and ni with increasing fractionation which is interpreted to reflect a transition to a more evolved sulfide liquid that segregated in the eastern parts of the intrusion in massive sulfide ores merenskyite forms unusually large up to 5000 m2 euhedral grains commonly in contact with spherical silicate inclusions bms hosts 12 16 of the pd with the remainder hosted by pgm which is interpreted to indicate that merenskyite recrystallized from a pge bearing bismuthotelluride metamorphic melt formed during high grade metamorphism sperrylite ptas2 is the second most abundant pgm 18 of pgm in disseminated ore and in contrast to merenskyite occurs mainly as very small median of 25 m2 inclusions in high temperature silicates and oxides interpreted to have crystallized at high temperatures directly from sulfide blebs that formed and were transported within the limoeiro magma conduit

earthquake induced ground failures in italy abstract the national catalog of ground failures induced by strong earthquakes in italy cedit is described the catalog holds data on ground failures triggered by the earthquakes that occurred in italy in the last millennium and which had a nominal epicentral intensity equal to or greater than viii in the mercalli cancani sieberg mcs intensity scale the ground effects reported in the catalog are the following landslides fractures liquefaction surface faulting and topographic changes of the ground level subsidence settlements tilting and so on each effect is described in terms of seismological parameters of the triggering earthquake site coordinates and administrative code lithology and kinematic type of the ground failure the catalog represents a tool to assess the susceptibility of geologic materials to ground shaking and to validate predictive models of seismically induced ground displacements scenarios of earthquake induced geologic risks in the context of this study a simple statistical analysis of the database yielded useful relations between the parameters of the triggering earthquakes and the related effects

magma transport through the crust via interconnected sill complexes three dimensional seismic data from the volcanic margin offshore norway have been used to map the complex three dimensional geometry of two major sill complexes these data show that the complexes consist of bowl shaped or inclined sheetlike discordant sills that intersect with one another over a vertical distance of 8 12 km and transect basement and sedimentary rocks of the middle to upper crust using a simple graphical technique we demonstrate the interconnectedness of the sill complex and hence the maximum time for sill emplacement we show that sills are interconnected by junctions occurring systematically at the lowest points of the overlying sills and hence that the sill complex could have acted as a single throughgoing magmatic plumbing system transporting mafic melts from mid lower crustal depths to near surface based on this imaging of the magmatic plumbing system we conclude that sills can form viable and efficient conduits for crustal magma transport in volcanic margins and may play a role in feeding large extrusive complexes

ni cu pge magmatic sulfide deposits in the yangliuping area permian emeishan igneous province sw china the ni cu pge sulfide deposits in the yangliuping area sw china are hosted in mafic ultramafic sills the four mineralized sills are located in the yangliuping tectonic dome and intrude devonian carbonaceous marble graphitic schist the sills are 200 300 m thick and 1 000 2 000 m in strike length and now consist chiefly of serpentinite talc schist tremolite schist and meta gabbro disseminated ni cu sulfide mineralisation occurs in the serpentinite in the lower parts of the sills massive sulfide mineralisation is located in the base of the sills and in the footwall along fractures beneath the mineralized serpentinite although the sulfide ores have been modified by hydrothermal activity there are relict cumulate textures in the disseminated sulfides indicating a magmatic origin for the ores the yangliuping intrusions and the dashibao formation have similar primitive mantle normalized trace element and platinum group element pge patterns indicating that they are derived from a common parental magma type the positive correlation between cu concentrations and cu zr ratios of the dashibao formation basalts indicates that the chalcophile elements were removed before eruption we propose that fractional crystallization of the yangliuping magma accompanied by the introduction of s and co2 from the wall rocks caused the magma to become s saturated leading to the segregation of magmatic sulfides that became enriched in ni cu pge the sills acted as conduits for the overlying dashibao formation basalts with the sulfide liquid along with early crystallizing olivine and pyroxene segregating from the magma as it passed through the conduits prior to eruption

timing of crust formation deposition of supracrustal sequences and transamazonian and brasiliano metamorphism in the east pernambuco belt borborema province ne brazil implications for western gondwana assembly abstract the main structural feature of the central domain of borborema province ne brazil is a network of dextral and sinistral shear zones these shear zones rework an older regionally developed flat lying foliation in orthogneisses and supracrustal belts which in the east pernambuco belt was formed under amphibolite facies conditions this study reports la icp ms u pb zircon ages of metaigneous and metasedimentary rocks aiming to constraint the pre transcurrent tectonothermal evolution in the eastern pernambuco domain ages of 2125 7 and 2044 5 ma in a mafic layer of banded orthogneiss are interpreted as the age of the protolith of the orthogneiss and of high grade transamazonian metamorphism respectively the latter age is consistent with the occurrence of low th u metamorphic zircon xenocrysts dated at 2041 15 ma in the leucosome of a migmatitic paragneiss a granitic orthogneiss dated at 1991 5 ma reflects late to post transamazonian magmatic event a similar age 1972 8 ma was found in rounded zircon grains from a leucocratic layer of banded orthogneiss ages of detrital zircons in a paragneiss sample indicate derivation from sources with ages varying from the archean to neoproterozoic with peak ages at ca 2220 2060 1940 1200 1150 and 870 760 ma detrital zircons constrain the deposition of the supracrustal sequence to be younger than 665 ma magmatic zircons with the age of 626 15 ma are found in the leucosome of a migmatitic paragneiss and constrain the age of the brasiliano high temperature metamorphism a lower intercept age of 619 36 ma from a deformed granodiorite dated at 2097 5 ma and the crystallization age of 625 24 ma of the felsic layer of banded orthogneiss also confirm the late neoproterozoic metamorphism these results show that the present fabric in basement and supracrustal rocks was produced during the brasiliano orogeny paleoproterozoic ages reported in this study are similar to those found in other sectors of the borborema province the cameroon and nigeria provinces and the sao francisco congo craton they show the importance of the transamazonian eburnean event and suggest that these tectonic units may have been part of a larger single continental landmass likewise similarities in post transamazonian metamorphic and magmatic events in the borborema nigeria and cameroon provinces suggest that they shared a common evolution and remained in close proximity until the opening of the atlantic ocean

the perseverance ultramafic complex western australia the product of a komatiite lava river the perseverance ultramafic complex is a body of olivine rich komatiitic rocks spatially associated with the agnew nickel deposit in the agnew wiluna greenstone belt of the archaean yilgarn block in western australia the complex consists of a central lenticular body up to 700 m thick of olivine adcumulates flanked by laterally extensive sheet like bodies of olivine orthocumulates and spinifextextured komatiite flows rocks progressively further away from the central lens have chemical compositions reflecting higher original proportions of komatiite liquid to cumulus olivine parent liquids had mgo contents between 25 and 32 mgo approximately chondritic al ti ratios and hree patterns and moderate depletion in lree olivines within the adcumulate lens show a progressive increase in forsterite content from fo93 at the bottom to fo94 5 at the top calculated original olivine compositions in ihe flanking rocks are similar to those at the base of the central lens original olivine nickel contents show a symmetrical variation from maximum values of 3500 ppm at the top of the central lens through minimum values of 1000 ppm at the base and margins of the central lens to intermediate values in the distal rocks the complex as a whole shows evidence for nickel depletion relative to other komatiite suites these observations are explained in terms of prolonged eruption and flow of komatiitic lava down a major flow channel or lava river adcumulates crystallized on the floor and sides of the central channel which was formed at an early stage by thermal erosion of floor rocks episodic overflow of the central channel produced distal flood plain rocks consisting of olivine orthocumulates and layered flows lavas became more magnesian and nickel rich with time giving rise to the observed spatial variation in primary olivine composition nickel depletion of the earliest lavas is attributed to pre eruption segregation of large volumes of immiscible fe ni sulfide which were concentrated to form the underlying agnew nickel deposit

the luanga deposit carajas mineral province brazil different styles of pge mineralization hosted in a medium size layered intrusion abstract the luanga complex located in the eastern portion of the carajas mineral province is part of a cluster of pge mineralized layered intrusions grouped into what is known as the serra leste magmatic suite the luanga deposit the largest pge deposit in south america has two distinct styles of pge mineralization the first type termed as sulfide zone consists of a 10 50 m thick interval with disseminated base metal sulfides pentlandite pyrrhotite chalcopyrite located along the upper contact of the intrusion s ultramafic zone the sulfide zone extends along the entire length of the intrusion 3 km and hosts the bulk of pge resources of the luanga complex i e 142 mt at 1 24 ppm pt pd au and 0 11 ni the second type of pge mineralization termed as low s high pt pd zones consists of 2 10 m thick stratabound pge mineralization within a sequence of interlayered ultramafic and mafic cumulates located above the sulfide zone host rocks of the low s high pt pd zones consist mainly of sulfide and chromite free harzburgite and orthopyroxenite these mineralized rocks do not show any distinctive texture or change in modal composition the sulfide zone and low s high pt pd zons have distinct pge distribution the sulfide zone has pt pd ratios of 0 52 and a positive correlation between pge and s the low s high pt pd zones have pt pd ratios of 1 2 and depletion in ipge relative to primitive mantle the platinum group minerals pgm observed in the sulfide zone are predominantly pt pd bismuthtellurides stanides and arsenides mainly enclosed within sulfide minerals in contrast the pgm observed in low s high pt pd zones are mainly pt arsenides stannides and antimonides mostly enclosed within alteration silicates differences in texture geochemistry and pgm assemblage between these mineralization styles suggest that they originated from distinct geological processes the sulfide zone was formed by a major event of segregation of an immiscible sulfide liquid whereas the low s high pt pd zones formed by a sulfide liquid saturation followed by sulfur loss during post magmatic alteration the identification of pge rich layers in rocks without sulfides or chromite at the carajas mineral province is important as these may have been overlooked during previous exploration programs

the santa rita nickel sulfide deposit in the fazenda mirabela intrusion bahia brazil geology sulfide geochemistry and genesis the santa rita ore zone within the fazenda mirabela intrusion is an unusual example of high tonnage magmatic ni cu pge sulfide mineralization developed as a stratiform layer within the main cumulus sequence of a layered intrusion the intrusion as a whole is about 4 2 5 km in outcrop dimensions and at least 3 km in original maximum stratigraphic thickness with an original boat shaped morphology the ore zone comprises a 50 to 200 m thick interval containing up to 5 wt percent disseminated sulfides within a sequence of mostly unaltered harzburgites and orthopyroxenites this orthopyroxene dominated sequence lies between the dominantly olivine rich cumulates that comprise the lower half of the intrusion and the gabbroic cumulates that make up the upper half sulfide tenor variations and silicate host rock compositions have been derived from a very large database of continuous assays of more than 500 diamond drill cores consistent patterns of sulfide tenor gradually decreasing ni from over 20 to about 10 wt percent near constant cu and gradually decreasing pges with cyclically varying pt pd ratios are found within the santa rita ore zone across the entire intrusion and display relatively little lateral variability the position of the sulfide mineralization envelope within the harzburgite orthopyroxenite package migrates to higher stratigraphic levels from the northern to the southern margin of the intrusion maximum grades and thicknesses correlate with the maximum thickness of orthopyroxene bearing cumulates asymmetrically disposed toward the southern margin of the intrusion nickel tenors of the sulfides range from 15 to 25 wt percent exceptionally high for rocks with relatively low values of mgo mgo feo and are closer to the typical values observed in komatiite hosted deposits although cu tenors typically 5 8 wt are much higher than komatiite values sulfide pge tenors range from less than 100 ppb to greater than 10 ppm of both pt and pd with maximum values in s poor rocks at the base of the sulfide bearing interval pges become significantly more depleted toward the top of the santa rita zone we attribute these features along with the localization of the sulfide bearing interval at the contact between ultramafic and mafic cumulates to mixing of an initially s undersaturated moderately ni enriched resident magma with a relatively low ni pge depleted significantly lower temperature replenishing magma charged with suspended sulfide liquid droplets

behavior of a 31m high excavation supported by anchoring and nailing in residual soil of gneiss abstract a 31 m high excavation located at niteroi rj in residual soil from gneissmigmatite with high nspt 40 was performed for a building construction two levels of anchored walls were considered in order to guarantee stability when the construction of the upper wall was almost completed a crack parallel to the direction of the wall formed in the hilltop it was decided that the construction works would cease in order to perform additional studies the presence of reasonably continuous soil layers of different colors gray white and red with thicknesses varying from a few millimeters to some centimeters clearly observed in the face of the cut slope the inclination of these soil layers varied along the length of the excavation and they were in an orientation that was unfavorable for the stability of the cut laboratory tests were performed and the presence of high activity clay mineral and low shear resistance parameters was determined for the gray clayey sand soil those weakness planes i e the thin layers of gray clayey sand had not been properly detected in the previous studies that supported the design of those walls considering these new findings the original project was reviewed and it was decided that soil nailing would be used for accomplish the excavation to the original planned level the upper wall was also reinforced with additional anchors load measurements in the nails indicated that the stress state in the soil mass corresponded to the active condition at the final level of excavation significant lateral movements were measured and varied according to the direction and inclination of the cited weakness planes it was observed that the reliquiae planes were fundamentally important to the behavior of the excavation

structural lithological and geochemical constraints on the dynamic magma plumbing system of the jinchuan ni cu sulfide deposit nw china eastern and western portions of the jinchuan ultramafic intrusion have previously been interpreted as dismembered segments of a single elongate intrusion by late faults however the different stratigraphic sequences of the two portions indicate that they are originally two separate intrusions referred to as eastern and western intrusions in this study the eastern intrusion is characterized by a concentric distribution of rock types with a core of sulfide dunite enveloped by lherzolite whereas the western intrusion is composed of the upper and lower units interpreted as magmatic mega cycles with regular variations in lithology and chemistry in the western intrusion the upper unit consists of fine grained dunite lherzolite and pyroxenite from its base to its top the mgo contents decrease upward from the dunites 42 45 wt to the lherzolites 36 41 wt while al2o3 and incompatible elements increase upward in contrast the lower unit consists of coarse grained dunites and lherzolites containing 37 40 and 28 35 wt mgo respectively sharp contacts between the upper and lower units and fine grained dunite xenoliths at the top of the lower unit indicate that the lower unit intruded along the base of the upper unit disseminated and net textured sulfides primarily occur in the lower unit and comprise the no 24 ore body very low s contents 100 ppm of the wall rocks at jinchuan indicate that they were not the source of s causing sulfide immiscibility sulfide segregation more likely occurred in deep seated magma chambers and sulfides were deposited in the western intrusion when sulfide bearing magmas passed through the intrusion in contrast the eastern intrusion was formed by injections of sulfide free and sulfide bearing olivine crystal mushes respectively from another deep seated staging magma chamber the eastern and western intrusions and the deep seated magma chambers comprise a complicated magma plumbing system at jinchuan normal faults played a significant role in the formation of the magma plumbing system and provided pathways for the magmas

seismically induced landslides by a low magnitude earthquake the mw 4 7 ossa de montiel event central spain this work has been funded by spanish ministry of economy and competitiveness research project cgl2011 30153 c02 02 and by the research groups rnm 374 junta de andalucia tectac ucm 910368 and vigrob 184 universidad de alicante mr loffredo acknowledges funding of the universita di roma la sapienza post graduate grant concorso a n 480 area cun 04

attenuation of intensity with epicentral distance in the iberian peninsula we have classified the attenuation of the medveded sponheuer and karnik msk intensity into five types each as a function of the epicentral intensity i o based on the mean radii of 254 isoseismal maps mainly historical earthquakes in the iberian peninsula geographically representing each earthquake with its corresponding attenuation tendency it can be seen that those with low attenuation lie west of the peninsula and those with high attenuation in the south and east this regionalization seems to be due as much to the seismotectonic characteristics different crustal types and size of the earthquakes as to the different construction types in each region these attenuation values are similar to those of southern europe but much higher than those found in the united states from the point of view of seismic hazard evaluation these laws represent an improvement with regard to those used so far we have extended previous attenuation studies to the whole of the iberian peninsula and in some points differences of attenuation assignment of almost two degrees of intensity have been corrected

sulfur isotopic studies of continental flood basalts in the noril sk region implications for the association between lavas and ore bearing intrusions previous studies of both ore and non ore bearing intrusives in the permo triassic flood basalts of the siberian platform in the noril sk area have shown that high grade ni cu platinum group elements pge mineralization is associated with anomalously high 34s values of 8 to 12 in addition several researchers have proposed that observed depletions in the cu ni and pge content of basaltic lavas of the nadezhdinsky nd formation are related to diffusional exchange with and upgrading in metal tenor of sulfides in the volcanic conduit system sulfur isotopic studies of the lavas at noril sk were initiated to determine if interaction with crustally derived sulfur in the conduit system was evident and if the nd lavas in particular were characterized by an anomalous isotopic signature 34s values of the lavas range from 4 5 to 8 7 vienna canon diablo troilite vcdt with s concentrations from 40 to 1373 ppm the majority of 34s values range from 0 to 4 and are similar to those from s poor intrusions in the noril sk area although textural data are not supportive of early sulfide saturation and the presence of immiscible sulfide droplets in the lavas recrystallization may have erased expected mineralogical and textural evidence mineralogical data indicate that hydrothermal alteration of the lavas has occurred but s redistribution has been restricted to localized areas and 34s values have not been affected the relatively low s concentrations of the lavas are thought to be due in large part to degassing of the lavas in the shallow conduit system and during eruption our calculations are consistent with the premise that degassing of basaltic magmas at temperatures in excess of 900 c at qfm leads to only minor 34s depletion of sulfur remaining in the melt and decreases in 34s values of less than 2 at 90 degassing for this reason all lavas with 34s values in excess of 2 require a contribution of 34s enriched country rock sulfur because of the high s content and 34s value 16 20 of evaporites in the country rocks at noril sk contamination of less than 0 5 is required to explain the most 34s enriched lavas the nd lavas have an average 34s of 2 9 but show no difference in s isotopic composition relative to the other lavas suggesting that metal depletion involved only limited s transfer or that exchange between mantle derived s and s of crustal origin buffered 34s values to less than 5 anomalously positive 34s values similar to those of the ore bearing intrusives in the noril sk region are not consistently found in low s rocks either lavas or intrusives although the mechanism for the derivation of sulfide in the ore bearing intrusions remain speculative it is clear that the formation of sulfide ores characterized by high metal tenors proceeded only in the presence of sulfur of crustal origin

the nain churchill boundary and the nain plutonic suite a regional perspective on the geologic setting of the voisey s bay ni cu co deposit northern labrador is the site of two major lithotectonic elements of eastern canadian shield geology first it encompasses a paleoproterozoic continental suture zone archean rocks of the nain province tectonically juxtaposed against paleoproterozoic and reworked archean rocks of the churchill province the nain churchill suture evolved between 1860 and 1740 ma impressing upon the archean and paleoproterozoic rocks a regional metamorphic and tectonic signature referred to as the torngat orogen an important component of the torngat orogen is the tasiuyak gneiss a paleoproterozoic metasedimentary unit that occupies most of the eastern margin of the churchill province second northern labrador is the site of a world renowned terrane of mesoproterozoic anorogenic igneous rocks the nain plutonic suite that sits astride the suture and acts as a stitching batholith between the nain and churchill provinces the nain plutonic suite comprising amalgamated granitic anorthositic dioritic and troctolitic intrusions largely obscures the suture for nearly half of its total length the suite evolved between 1350 and 1290 ma and is interpreted as a product of magmatism associated with limited intracontinental rifting of the conjoined nain churchill crust above a mantle plume the voisey s bay ni cu co deposit serendipitously discovered in 1993 resides within one of the oldest troctolitic intrusions of the nain plutonic suite a 1334 ma intrusion that transgresses a contact between archean and paleoproterozoic gneisses genetic controls on the setting of mineralization have been built upon the nain churchill boundary as a zone of weakness that was exploited by mantle magmas and have implicated the tasiuyak gneiss as a crustal sulfur source although the archean paleoproterozoic junction at voisey s bay is presently interpreted as representing the nain churchill boundary in reality the provincial affinity of the archean gneisses is equivocal this uncertainty dictates caution in assigning the nain churchill boundary as the convenient transcrustal conduit that allowed the voisey s bay mafic intrusions rapid transit from their mantle staging area modeling the sulfide deposit as being solely a result of sulfur saturation of mafic magma by proximal paleoproterozoic tasiuyak paragneisses is also questionable because other genetic processes may have been responsible for example desilication of gneiss is strongly indicated by aluminous refractory minerals in vestiges of fused tasiuyak gneiss the spatial distribution of the mineralized rock at voisey s bay apparently within the subchamber plumbing system feeding a larger intrusion and within remnants of the larger intrusion itself may serve as a paradigm for similar deposits in the nain area but the preerosional comparative morphology of that larger intrusion relative to the better preserved ones may never be known a thorough understanding of the setting and genesis of the voisey s bay deposit will better facilitate establishing exploration targets in other parts of the nain region in labrador as a whole and in other geologically similar regions of the world

siderophile and chalcophile elemental constraints on the origin of the jinchuan ni cu pge sulfide deposit nw china abstract the jinchuan deposit nw china is one of the world s most important ni cu pge sulfide deposits related to a magma conduit system and is hosted in an ultramafic intrusion the intrusion is composed of lherzolite and dunite with the two largest sulfide ore bodies named as ore body 1 and 2 in its middle portion the sulfide ores may be disseminated net textured or massive the disseminated and net textured sulfide ores are characterized by variable but generally low pge concentrations 10 3200 ppb pt 240 9800 ppb pd 17 800 ppb ir 25 1500 ppb ru and 15 400 ppb rh in 100 sulfides the massive sulfide ores are extremely low in pt 4 to 4 5 10 5 the low pge contents suggest that the sulfide ores formed from the silicate magmas that had already experienced prior sulfide separation our calculations indicate that if the first stage basaltic magmas had contained 6 3 ppb pt 6 2 ppb pd and 0 1 ppb ir 0 008 sulfide removal would result in pge depletion in the residual magma with 0 57 ppb pt 0 25 ppb pd and 0 009 ppb ir the jinchuan sulfides were formed by a second stage of sulfide segregation from a pge depleted magma under silicate sulfide liquid ratios r factor ranging from 10 3 to 10 4 in a deep seated staging chamber the massive sulfide ores and some of the net textured sulfide ores exhibit strong negative pt anomalies that cannot be explained by sulfide segregation under variable r factors instead the sulfide melts that formed the massive ores were segregated from magmas experienced prior fractionation of pt fe alloy alternatively the pt may have been selectively leached by hydrothermal fluids during remobilization of the sulfide melts that produced the massive sulfides which occur in cross cutting veins we propose that the jinchuan intrusion and ore bodies were formed by injections of sulfide free and sulfide bearing olivine mushes from a deep seated staging chamber

formation of the jinchuan ultramafic intrusion and the world s third largest ni cu sulfide deposit associated with the 825 ma south china mantle plume we report here shrimp u pb geochronological geochemical and nd isotopic data for the jinchuan ultramafic intrusion gansu province china which hosts the world s third largest magmatic ni cu sulfide deposits u pb baddeleyite analyses yield an age of 812 26 ma for the ultramafic intrusion this age is indistinguishable within analytical uncertainties from the u pb zircon ages of 827 8 ma and 828 3 ma for the sulfide bearing ultramafic rocks and the dolerite dykes that cut the ultramafic intrusion respectively these u pb dating results show beyond doubt that the jinchuan ultramafic intrusion and associated ni cu sulfide deposit were formed at 825 ma rather than 1500 ma as has been widely believed the ultramafic rocks exhibit large negative nd t values 8 9 to 12 0 that decrease with increasing la sm suggesting that their parental magmas were derived from a long term enriched lithospheric mantle and experienced crustal contamination mineralogical petrological and geochemical data all indicate that the jinchuan intrusion was generated by melting of the enriched lithospheric mantle heated by an anomalously hot plume the u pb ages of 825 ma for igneous baddeleyites and zircons and 900 880 ma for inherited zircons in the jinchuan mafic ultramafic rocks are comparable with those in the qaidam block and qilian belt the western extension of the qinling belt that was likely derived from northern yangtze craton the jinchuan ni cu sulfide bearing intrusion along with coeval regional plume related mafic dykes and tholeiites and mafic ultramafic complexes with associated v ti and ni cu pge mineralization is interpreted to be genetically related to the 825 ma south china mantle plume

field relationships and geochemical constraints on the emplacement of the jinchuan intrusion and its ni cu pge sulfide deposit gansu china field mapping and petrological geochemical investigation of the jinchuan intrusion in north central china clarifies how the intrusion was emplaced and provides a new model that explains how its large and rich ni cuplatinoid deposits may have formed the intrusion was emplaced into high grade gneisses and marbles along a disconformity at the base of an overlying cover sequence indicating that it was emplaced as a sill not a nearvertical dike as previously proposed after emplacement the intrusion was rotated to its present orientation and deformed and metamorphosed under greenschist facies conditions relative enrichment of incompatible trace elements coupled with negative u th and nb ta anomalies in all samples from the intrusion provide evidence that the parental magma assimilated granitoid rocks in the lower crust the presence of abundant marble xenoliths now decarbonatized to diopside rich skarns and chemical indices such as high cao sio2 indicate that the magma assimilated carbonate on reaching its present site this contamination may be linked to the formation of the ni cu platinoid ores we propose that the assimilation of carbonate rich fluids increased the oxygen fugacity of the magma and led to the segregation of metal rich sulfides

olivine and sulfur isotopic compositions of the uitkomst ni cu sulfide ore bearing complex south africa evidence for sulfur contamination and multiple magma emplacements the uitkomst complex in northern south africa is host to a ni cu deposit containing a minerable reserve of 2 9 mt massive ore with grades of 2 ni 1 cu and 6 ppm pt pd and an indicated plus inferred resource of 98 mt disseminated ore with grades of 0 6 ni 0 2 cu and 1 ppm pt pd based on similar age and composition to that of the bushveld complex the uitkomst complex is believed by some investigators to be a satellite body of the bushveld complex it has a tubular shape with an exposed surface area of about 0 8 8 km and a thickness of up to 1000 m apparently exploiting the bedding planes of gently dipping footwall sediments that include shale quartzite and dolomite the uikomst complex comprised of stratiform mafic and ultramafic rock units that from base to top include gabbro sulfide mineralized harzburgite unmineralized harzburgite pyroxenite gabbronorite and gabbro the compositions of olivine from different rock units are significantly different olivines from the gabbronorite unit are highly fractionated containing 30 mol fo forsterite mg2sio4 and 300 ppm ni olivines from the underlying pyroxenite and harzburgite units are much more primitive containing 86 91 mol fo abrupt changes in the contents of ni in olivine occur within the pyroxenite unit and between the mineralized and unmineralized harzburgite units the contents of ni in olivine from the unmineralized harzburgite unit are between 2900 and 3600 ppm the contents of ni in olivine from the underlying mineralized harzburgite units are 1500 ppm lower olivines from the lower part of the pyroxenite unit are similar to olivines from the underlying harzburgite unit whereas olivines from the upper part of the pyroxenite unit contain much lower ni 600 ppm numerical modelling suggests that the strikingly different compositions of olivine are related to different parental magmas with different mgo feo ratios and or ni contents the 34s values of the basal gabbro and unmineralized rock units range from 0 9 to 2 6 which are similar to typical mantle values 0 3 in contrast the 34s values of the sulfide ores in the harzburgite units are significantly lower varying between 2 6 and 7 1 the low 34s values of the sulfide ores indicate addition of 34s depleted crustal sulfur the obvious sources of such crustal sulfur are the malmani dolomite and the timebal hill shale that contain pyrite with negative 34s values up to 11 and 18 respectively sulfide saturation in the magma of the mineralized harzburgite units is thought to have resulted from addition of the crustal sulfur the resulting immiscible sulfide liquid droplets were then concentrated in the base of the magma channel some of the sulfide liquid was expelled into the basal gabbro that separated the active magma channel from the footwall quartzite new magma then entered the channel displacing most of the resident magma to form the unmineralized harzburgite the overlying pyroxenite gabbronorite and gabbro units formed either by in situ differentiation of the same magma giving rise to the underlying unmineralized harzburgite or by subsequent emplacement of a more evolved magma

the limoeiro deposit ni cu pge sulfide mineralization hosted within an ultramafic tubular magma conduit in the borborema province northeastern brazil the limoeiro deposit located in a high grade mobile belt of the brasiliano orogenic cycle 650 500 ma represents one of the few magmatic ni cu pge sulfide discoveries in recent years the deposit is hosted by an ultramafic chonolith consisting in a partly deformed and metamorphosed tube like body affected by brittle faults within high grade gneiss and schist the absolute age of the ultramafic intrusion that hosts the limoeiro deposit is not yet known but regional geologic constraints suggest that both intrusion and host rocks belong to a terrane older than the orogenic cycle peak metamorphic parageneses of the ultramafic intrusion and country rocks indicate granulite facies of metamorphism interpreted as the result of the neoproterozoic brasiliano orogenic cycle the limoeiro deposit is the first significant discovery of ni cu sulfide in the borborema province opening a new window for exploration in this large orogenic belt despite the high grade metamorphism and the tectonic deformation the primary magmatic structure of the intrusion hosting the limoeiro deposit is remarkably well preserved this intrusion forms a tube like conduit chonolith with cross sections a few hundreds of meters in diameter and with a considerable length of more than 4 km the conduit consists of two distinct sequences of ultramafic rocks denominated upper and lower sequences each one consisting of a core of harzburgite enveloped by orthopyroxenite with an irregular and discontinuous outer shell of amphibolite these ultramafic sequences characterized by similar composition and structure have distinctively different s contents resulting from the presence of disseminated ni cu sulfide mineralization only in the upper sequence the magmatic system of the limoeiro deposit is interpreted to result from the input of two major pulses of magma with similar composition but sulfide saturation and segregation is restricted to the second magma pulse upper sequence nickel cu pge sulfide mineralization is broadly concordant with the upper sequence and different orebodies resulted from tectonic slicing of the originally continuous tube like structure the bulk of the mineralization in all orebodies consists of thick up to 150 m and elongated up to 1 km masses of rock containing disseminated sulfides broadly concordant with the chonolithic structure thin layers of massive ore occur in the lower portions of some of the orebodies and represent about 3 vol of the limoeiro deposit the intrusion hosting the limoeiro deposit is probably the best preserved chonolith that has been overprinted by granulite facies metamorphism within an orogenic terrane this study indicates that reconstruction of small magma conduits an important tool for exploration for ni cu sulfide deposits may be successfully achieved within high grade orogenic terranes

the age distributions of detrital zircons in metasedimentary sequences in eastern borborema province ne brazil evidence for intracontinental sedimentation and orogenesis detrital zircons in metasedimentary rocks attributed to three different complexes in the central and pernambuco alagoas domains of the borborema province northeastern brazil were dated by la icpms two samples from each of the following complexes were analyzed sert nia and surubim in the central domain and rio una in the pernambuco alagoas domain one sample of the sert nia complex yielded only paleoproterozoic zircons whereas neoproterozoic zircons predominate in the other with the youngest zircon indicating deposition after 642 ma one of the samples of the surubim complex yielded again only paleoproterozoic concordant zircon ages in the other sample although paleoproterozoic zircons predominate ages vary from the mesoarchean to the neoproterozoic the age of the youngest zircon in this latter sample indicates deposition after 850 ma and an overgrowth on an archean grain yielded an age of 623 6m a 2 interpreted as the age of peak metamorphism the two samples of the rio una complex yielded predominantly detrital zircons with ages in the ranges 2 2 2 1 ga and 1 7 1 6 ga in this complex the youngest detrital zircon suggests deposition after 917 ma and metamorphic zircons indicate peak metamorphic conditions between 600 ma and 617 ma the results of this study together with available data from the literature allow the following conclusions a the sert nia complex is a neoproterozoic sequence and not paleoproterozoic as previously thought b the similarity in lithological associations detrital zircon populations and c isotope signature between the sert nia and surubim complexes suggest that they belong to the same lithostratigraphic unit c although the rio una complex can be older than the sert nia surubim complex the lack of zircons younger than 900 ma can also result from insufficient sampling or absence of young rocks alongside the drainage system that collected detritus to this complex d the regional metamorphism related to the brasiliano orogeny attained its climax at 630 600 ma e the age spectra of detrital zircons require their derivation from erosion of rocks formed not only during known geological events in the borborema province and in the nearby sao francisco congo craton but also from the amazonian craton suggesting accumulation in an intracratonic setting within a preexisting large continent f the short timespan between deposition and orogenic deformation may explain the overall medium to high temperature metamorphism due to maintenance in the subsequent compressional event of the elevated geothermal gradients produced during broad scale lithosphere extension

supported excavations observational method and inverse modeling an inverse analysis procedure that uses construction monitoring data to update predictions of deformations for supported excavation systems is presented the numerical procedure is used to optimize the finite element model of a 12 2 m deep excavation through chicago glacial clays by minimizing the errors between monitoring data and computed displacements the field observations are obtained from inclinometer data that measured lateral movements of the soil behind the supporting walls on opposite sides of the excavation throughout construction five construction stages are defined for the inverse analysis at every new construction stage the inclinometer data relative to that stage are added to the observations already available to recalibrate the model of the excavation the constitutive responses of the soils are represented by the hardening soil h s model of the six basic h s input parameters only one parameter per layer is optimized while the other parameters are either kept constant or related

can low magnitude earthquakes act as a triggering factor for landslide activity examples from the western carpathian mts poland abstract there are numerous examples of the impact of strong earthquakes on landslide activity there is however very little information about the ability of low magnitude earthquakes m

characteristics of ni cu pge mineralization and genesis of the jinchuan deposit northwest china the jinchuan ni cu sulfide deposit is hosted by a northwest striking ultramafic body located at the southwest margin of the sino korean platform china sulfide mineralization occurs in the lower part of the intrusion and comprises three main orebodies 24 and 1 in the west and 2 in the east of the intrusion three types of sulfide ores are identified net textured disseminated and a small amount of massive ore which occurs only in orebody 2 the principal ore minerals are pyrrhotite pentlandite violarite chalcopyrite and cubanite a systematic study has been made of the s ni cu co platinum group elements pge and au of the ore samples a lateral zonation is defined by these elements in the two western orebodies the concentrations of ni cu and pge increase from the margins toward the center of the orebodies this trend is also present when the metal elements are normalized to the s content of the samples a vertical variation of elements is present in the east orebody where the amounts of ni cu and pge as well as s decrease upward however when normalized to the s content pge increase upward but ni and cu remain more or less constant a plot of pge versus s clearly shows three sample sets 1 samples from orebody 24 have lower s contents mostly less than 5 wt percent and their pge contents roughly increase with that of sulfur 2 orebody 1 has higher pge contents but the pge plots are more scattered suggesting multiple processes during pge mineralization and 3 orebody 2 has very low pge concentrations ore samples studied show an average ni cu ratio of 2 and pt pd ru ir os ratios of 5 to 30 with most values falling in the range of 10 to 15 these are typical features of sulfide ores that relate to mafic magma there is little difference in the pt pd os ir ru ratios and the chondrite normalized pge distribution patterns between the pge rich and pge poor ores suggesting that they originated from magmas with similar major element compositions the close association of pge enrichment with sulfide mineralization and the strong correlations exhibited in all ore types between s and ni co and pge indicate that the ores are the consequence of the segregation of sulfide from silicate magmas the high pge contents of ore bodies 24 and 1 and the low pge contents of orebody 2 suggest that two batches of sulfide liquid were involved the pge rich sulfide liquid equilibrated with a relatively primitive silicate magma whereas the pge poor sulfide liquid equilibrated with a silicate magma from which pge had been depleted by prior probably fractional sulfide segregation the low values of ni cu ratios about 2 and high values of pt pd ru ir os ratios 10 15 of the samples together with the chemical composition and rare earth element data of the intrusive rocks provide convincing evidence that the initial magma of the intrusion was gabbroic rather than ultramafic

earthquake induced landslides in central america central america is a region of high seismic activity and the impact of destructive earthquakes is often aggravated by the triggering of landslides data are presented for earthquake triggered landslides in the region and their characteristics are compared with global relationships between the area of landsliding and earthquake magnitude we find that the areas affected by landslides are similar to other parts of the world but in certain parts of central america the numbers of slides are disproportionate for the size of the earthquakes we also find that there are important differences between the characteristics of landslides in different parts of the central american isthmus soil falls and slides in steep slopes in volcanic soils predominate in guatemala and el salvador whereas extensive translational slides in lateritic soils on large slopes are the principal hazard in costa rica and panama methods for assessing landslide hazards considering both rainfall and earthquakes as triggering mechanisms developed in costa rica appear not to be suitable for direct application in the northern countries of the isthmus for which modified approaches are required

experimental phase relations of hydrous peridotites modelled in the system h 2 o cao mgo al 2 o 3 sio 2 the hydration of peridotites modelled by the system h2o cao mgo al2o3 sio2 has been treated theoretically after the method of schreinemakers and has been investigated experimentally in the temperature range 700 900 c and in the pressure range of 8 14 kbar in the presence of excess forsterite and water the garnet to spinel peridotite transition boundary intersects the chlorite dehydration boundary at an invariant point situated at 865 5 c and 15 2 0 3 kbar at lower pressures a model spinel lherzolite hydrates to both chlorite and amphibole bearing assemblages at an invariant point located at 825 10 c and 9 3 0 5 kbar at even lower pressures the spinel to plagioclase peridotite transition boundary intersects the dehydration curve for amphibole forsterite at an invariant point estimated to lie at 855 10 c and 6 5 0 5 kbar both chlorite and amphibole were characterized along their respective dehydration curves chlorite was found to shift continuously from clinochlore with increasing temperature to more aluminous compositions amphibole was found to be tremolitic with a maximmum of 6 wt al2o3 the experimentally determined curves in this study were combined with the determined or estimated stability curves for hydrous melting plagioclase talc anthophyllite and antigorite to obtain a petrogenetic grid applicable to peridotites modelled by the system h2o cao mgo al2o3 sio2 that covers a wide range of geological conditions direct applications of this grid although quite limited can be made for ultramafic assemblages that have been extensively re equilibrated at greenschist to amphibolite facies metamorphism and for some highgrade ultramafic assemblages that display clear signs of retrogressive metamorphism

noril sk talnakh cu ni pge deposits a revised tectonic model the noril sk mining district is located at the northwest margin of the tunguska basin in the centre of the 3 000 4 000 km siberian continental flood basalt cfb province this cfb province was formed at the permo triassic boundary from a superplume that ascended into the geometric centre of the laurasian continent which was surrounded by subducting slabs of oceanic crust we suggest that these slabs could have reached the core mantle boundary and they may have controlled the geometric focus of the superplume the resulting voluminous magma intruded and erupted in continental rifts and related extensive flood basalt events over a 2 4 ma period cu ni pge sulfide mineralization is found in olivine bearing differentiated mafic intrusions beneath the flood basalts at the northwestern margin of the siberian craton and also in the taimyr peninsula some 300 km east of a triple junction of continental rifts now buried beneath the mesozoic cenozoic sedimentary basin of western siberia the noril sk i and talnakh oktyabr sky deposits occur in the noril sk kharaelakh trough of the tunguska cfb basin the cu ni pge bearing mineralized intrusions are 2 3 km wide and 20 km long differentiated chonoliths previous studies suggested that parts of the magma remained in intermediate level crustal chambers where sulfide saturation and accumulation took place before emplacement the 5 7 km thick neoproterozoic to palaeozoic country rocks containing sedimentary cu mineralization and evaporites may have contributed additional metal and sulfur to this magma classic tectonomagmatic models for these deposits proposed that subvertical crustal faults such as the northeast trending noril sk kharaelakh fault were major trough parallel conduits providing access for magmas to the final chambers however geological maps of the noril sk region show that the noril sk kharaelakh fault offsets the mineralization which was deformed into folds and offset by related reverse faults indicating compressional deformation after mineralization in the late triassic to early jurassic in addition most of the intrusions are sills not dykes as should be expected if the vertical faults were major conduits a revised tectonic model for the noril sk region takes into account the fold structure and sill morphology of the dominant intrusions indicating a lateral rather than vertical emplacement direction for the magma into final chambers taking into account the fold structure of the country rocks the present distribution of the differentiated intrusions hosting the noril sk i and talnakh oktyabr sky deposits may represent the remnants of a single 60 km long deformed and eroded palm shaped cluster of mineralized intrusions which are perceived as separate intrusions at the present erosional level the original direction of sill emplacement may have been controlled by a northeast trending paleo rise which we suggest is present at the southeastern border of the noril sk kharaelakh trough based on analysis of the unconformity at the base of the cfb the mineralized intrusions extend along this rise which we interpret as a structure that formed above the extensionally tilted block in the metamorphic basement geophysical data indicate the presence of an intermediate magma chamber that could be linked with the talnakh intrusion in turn this t shaped flat chamber may link with the yenisei khatanga rift along the northwest trending pyasina transform fault which may have served as the principal magma conduit to the intermediate chamber it then produced the differentiated mineralized intrusions that melted through the evaporites with in situ precipitation of massive disseminated and copper sulfide ore the noril sk kharaelakh crustal fault may not relate to mineralization and possibly formed in response to late mesozoic spreading in the arctic ocean

relationship between earthquake induced excess pore water pressure and strong ground motion observed in a monitored fill slope abstract the generation of excess pore water pressures during ground shaking can be an important earthquake induced landslide trigger we measured pore water pressures and seismic ground motion in filled slopes and examined their relationships obtained from 29 observed earthquakes we characterized pore water pressure and seismic waveforms by calculating several parameters that described their magnitudes and durations we demonstrate that whilst the instantaneous magnitude of strong ground motion is responsible for the generation of excess pore water pressure the magnitude of excess pore water pressure generated is related to the peak ground acceleration pga and arias intensity ai in the observed pga range of 0 12 1 9 m s2 the magnitude of peak ground velocity pgv also produced a strong correlation although a few exceptional events where long period component 1 s of seismic waves is dominant were observed lastly the time span over which excess pore water pressure continues to rise is affected by the duration of seismic ground motion our study shows how excess pore water pressures can be generated in fill slopes during seismic events this new knowledge could be used to improve future earthquake induced landslide hazard assessment

layered intrusions and volcanic sequences in central brazil geological and geochronological constraints for mesoproterozoic 1 25 ga and neoproterozoic 0 79 ga igneous associations abstract a 350 km long belt of layered complexes and associated volcano sedimentary sequences forms a continental scale feature exposed along the internal portion of the neoproterozoic brasilia belt in central brazil this study provides new geochronological results and a critical review of the available data of these igneous associations of central brazil precise age dating combined with geological and petrological studies indicate that this belt consists of two distinct igneous rock associations the 1 25 and 0 79 ga igneous episodes are constrained by reliable u pb zircon ages shrimp and id tims obtained in different regions and lithotypes of this belt both igneous associations were affected by high grade metamorphism and tectonism at ca 0 76 ga which partially disrupted the original igneous stratigraphy of the layered complexes and volcano sedimentary sequences the present configuration of this belt results from later events probably caused by final ocean closure and continental collision between the sao francisco and amazonian continents at ca 0 63 ga the 1 25 ga magmatic event represents an igneous rock association comprising extensive bimodal volcanic rocks palmeiropolis juscel ndia and indaianopolis sequences and associated large mafic layered intrusions serra dos borges and serra da malacacheta complexes geochemical data of mafic volcanic rocks indicate compositions similar to morb suggesting a tectonic setting where continental rifting led to the opening of an ocean basin large layered intrusions coeval to the volcano sedimentary sequence consist mainly of olivine plus plagioclase cumulates with abundant troctolite and leucotroctolite associated with olivine gabbro gabbro anorthosite and pyroxenite these layered intrusions are characterized by moderately primitive olivine compositions fo 63 76 positive nd 1250ma values low contents of incompatible trace elements and lree depleted mantle normalized ree patterns these features suggest an origin from the same depleted mantle source that produced the extensive morb type volcanism intrusion of layered complexes possibly occurred since the early stages of rifting being emplaced both at the base of and within the volcanic pile different magmatic ages and fractionation trends of layered bodies suggest that they represent a cluster of intrusions that originated during the time span of the continental to oceanic ridge rifting event the 0 79 ga igneous association consists of three large layered intrusions niquel ndia barro alto and canabrava complexes despite intense tectonism several striking geological similarities between the three separate bodies have been used to suggest that they originally constituted a single continuous magmatic structure these layered intrusion are characterized by thick ultramafic zones highly primitive compositions of olivine up to fo 93 and extensive fe enrichment trends of pyroxenes layered mafic ultramafic rocks have abundant evidence of crustal contamination including highly negative nd 800ma values as well as older crustal xenoliths and zircon xenocrysts cyclic units consisting of successive layers of dunite harzburgite orthopyroxenite websterite and gabbronorite occur throughout the stratigraphy of these layered intrusions the niquelandia complex ranks among the thickest layered intrusions in the world and together with the barro alto and canabrava layered intrusions represent an enormous volume of mantle derived magma emplaced into the crust during a continental rifting event the 1 25 and 0 79 ga rifting events are not exposed in the brasilia belt or in the sao francisco craton this supports previous interpretations suggesting that these igneous rock associations are part of an exotic block in the brasilia belt equivalent mesoproterozoic ca 1 25 ga and neoproterozoic ca 0 79 ga extensional events have been reported in other continents e g north america these igneous associations described within an allochtonous block in the brasilia belt provide additional constraints therefore for continental reconstruction models before the break up of rodinia

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

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

origin of extremely pge rich mafic magma system an example from the jinbaoshan ultramafic sill emeishan large igneous province sw china abstract the 260 ma jinbaoshan sill is part of the permian emeishan large igneous province in sw china and is mainly composed of wehrlite and hosts a pge deposit containing 45 tonnes of pt and pd with ore grades ranging from 1 to 5 ppm pt pd the sill is composed of several pge rich horizons at different stratigraphic heights a 5 m thick pge rich horizon at the base of the sill which is underlain by a chromite rich pge poor layer accounts for 44 of the total ore reserve the jinbaoshan sill is rich in pges with ir ranging from 1 7 to 138 ppb ru from 0 9 to 39 ppb rh from 3 1 to 133 ppb and a total pt and pd from 76 to 5371 ppb all the rocks from the sill display primitive mantle normalized chacophile element patterns enriched in pges relative to ni and cu the low cu pd ratios 20 to 1938 of the rocks relative to the primitive mantle cu pd 7000 imply that there was no sulfide fractionation of the magmas the pge enrichment of the sill indicates that it formed from extremely pge rich magmas modeling results show that such pge rich magmas likely resulted from a multistage dissolution upgrading process in an open magma conduit system large amounts of chromite crystallization triggered sulfide saturation when pge rich magmas emplaced into the upper magma chamber of the system settling and sorting of chromite and most sulfide liquids along with olivine resulted in the formation of the largest pge rich horizon at the base of the sill the rest minor sulfide liquid accumulated to form pge rich horizons in the middle part of the sill aided by turbulence and convection within the magma chamber

a model for the ni cu pge ores of the noril sk region and its application to other areas of flood basalt five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a high tio 2 type with alkalic affiliations ivakinsky and syverminsky suites 2 a tio 2 rich picrite bearing magma gudchichinsky suite 3 a picrite bearing tio 2 poor magma tuklonsky suite 4 a crustally contaminated tio 2 poor magma lower nadezhdinsky suite and 5 a picrite free magma mokulaevsky kharayelakhsky kumginsky and samoyedsky suites similar but not identical in its chemistry to the tuklonsky and separated from the lower nadezhdinsky by transitional suites upper nadezhdinsky and morongovsky the ni cu ores are associated with olivine rich intrusions that are geochemically similar to the mokulaevsky magma they are associated with about 1 15 to 1 10 of their mass in pge rich sulfides this requires that these sulfides equilibrated with 15 to 200 times more magma than is represented by the intrusions themselves following the model of naldrett et al 1992 it is proposed that crustal contamination of the original tuklonsky type magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the basalt magma with which the sulfides have come into contact and which shows chalcophile element depletion key metallogenic characteristics of the noril9sk region are 1 a hot region in the mantle giving rise to vast amounts of basalt 2 continental scale rifting 3 major faults serving as controls for extrusive and intrusive magmatism 4 crustal contamination of magma 5 chalcophile element depletion of contaminated magma 6 intrusion of magma that has inherited sulfide removed from the depleted magma and 7 the presence of evaporites in the sedimentary sequence underlying the basalts the simplest way to recognize chalcophile element depletion is to plot ni mgo vs mg number at mg mg 0 9fe total a strong indication that basalts have undergone crustal contamination is the correlation of high la sm ratios with high sio 2 contents the lake superior region shows many of the key metallogenetic characteristics of the noril9sk region including continental rifting a triple junction huge thicknesses of basalt and cu ni sulfide bearing intrusions duluth complex crystal lake gabbro some of the keweenawan basalts of the region show ni depletion correlated with chalcophile element depletion the region is an example of the potential application of the noril9sk model to exploration

the niquelândia mafic ultramafic complex goias brazil a contribution to the ophiolite x stratiform controversy based on new geological and structural data abstract the results of a geological structural mapping in a slice of the niquel ndia layered mafic ultramafic complex are presented the complex stratigraphy is made up of a possible basal zone the east mafic unit mainly gabbronorites with interlayered pyroxenites followed by the ultramafic unit mainly interlayered dunites and pyroxenites followed in turn by the central mafic unit mainly gabbronorites with minor interlayered pyroxenites and the serra dos borges unit mainly gabbros leuco troctolites and anorthosites at the upper part the most important tectonic feature all across the complex is the pervasive presence of westward dipping ns n10e ductile shear zones with well developed tectonic foliation parallel with the primary bedding the metamorphic paragenesis within the deformed zones progressively change from hypersthene granulite facies in the basal and central units to hornblende granulite facies and amphibolite facies in the upper unit some micro tectonic features described in the basal units are typical of alpine type peridotites and demonstrate that the basal cumulitic rocks underwent deformation and recrystallization under conditions generally considered to take place at the lower crust upper mantle at an estimate pressure of 8 10 kbar the tectonic features post date the primary late magmatic features like unmixing in pyroxenes and reaction coronas what indicate that the tectonic event is not closely related with the emplacement of the niquel ndia complex the niquel ndia complex is now considered as a single major stratiform mafic ultramafic complex which subsequently underwent tectonism with associated high grade metamorphism

widespread landslides induced by the mw 5 1 earthquake of 11 may 2011 in lorca se spain abstract on 11 may 2011 a moderate magnitude mw 5 1 earthquake struck the city of lorca se spain and nearby areas causing notable damage injuries and fatalities field inspection of the area affected allowed the location and characterization of more than 250 induced landslides mainly of disrupted type rock soil falls disrupted soil slides and rock avalanches this number was very high when compared with the inventories of previous events of similar magnitude mw 4 7 to 5 0 in the zone and with the results of previous models for predicting slope behavior during earthquakes several factors are proposed here to explain the observed differences i the comparatively high magnitude mw 4 5 of a foreshock of the seismic series that may have weakened the slopes ii the high peak ground motion values recorded for these events and iii the occurrence of topographic site effects the results of this study point out the importance of including such effects as improvements in the models for studying the regional behavior of slopes

up down or sideways emplacement of magmatic fe ni cu pge sulfide melts in large igneous provinces the preferential localization of fe ni cu pge sulfides within the horizontal components of dike sill lava flow complexes in large igneous provinces lips indicates that they were fluid dynamic tra

impact of tensile strength and incident angles on a soil slope under earthquake sv waves abstract the tensile strength and incident angles play important roles in seismically induced slope failures in this paper a new criterion for tension shear coupling is proposed based on several sets of relevant lab data and is verified using the experimental data provided by previous researchers this criterion can perfectly depict the tension region as well as the compression region in the entire stress space moreover the tension shear criterion was converted into an expression that could be directly used in a numerical method and it was verified by a numerical example in addition the sv waves were input using the equivalent nodal force method based on a viscous spring artificial boundary this process was implemented by the abaqus software and two numerical examples were used to verify this method subsequently based on the proposed new criterion and input method the impacts of the strength criterion and incident angles on an analysis of seismically induced slope failures were studied the results indicated that the evaluation of the tension shear region is extremely important in the analysis of the seismically induced slope failures the tensile strength of the seismically induced landslides was overestimated by the calculation of mohr coulomb criterion owing to the ambiguous description of the tensile failure or the tension shear failure the assessment of the slope stability was thus not conservative the incident angles of seismic waves affected the travel path and the directivity of slope seismic responses the sliding displacement of the slope side near the epicenter rose with increasing angles of wave incidence the critical slip surface deepened and the hazard aggravated therefore it is important to introduce both the tensile strength and incident angles when evaluating the stability of slopes subjected to seismic loads

geochemistry zircon u pb dating and hf isotopies composition of paleozoic granitoids in jinchuan nw china constraints on their petrogenesis source characteristics and tectonic implication abstract granitoids are widely distributed in jinchuan at the southwestern margin of the north china plate which is also an important area of mineral deposits the research subject of this article are two paleozoic granitoids a cataclastic syenogranite and a granodiorite porphyry this study presents whole rock geochemistry and zircon u pb hf isotope data for the two granitoids to determine their petrogenesis source characteristics and tectonic significance the cataclastic syenogranite is characterized by metaluminous composition with high potassium and la n yb n from 39 to 48 the composition with strong negative eu anomalies and zircon saturation temperatures t zr from 947 to 1072 c classify this intrusion as an a type granite the granodiorite porphyry is metaluminous with high sodium sub alkaline la n yb n ratios from 27 to 32 these i type intrusions have no eu anomalies and t zr ranges from 818 to 845 c both the cataclastic syenogranite and granodiorite porphyry show enrichment of lree and lile and depletion of hree and hfse except hf and zr using single zircon la icp ms u pb dating the emplacement age of the cataclastic syenogranite and granodiorite porphyry are determined at 433 4 3 7 ma and 361 7 4 6 ma respectively zircons from the cataclastic syenogranits have uniform negative e hf t values 11 0 5 to 9 0 5 implying the involvement of an old palaeoproterozoic crustal source in magma genesis the zircons from the granodiorite porphyry have e hf t values that range from 8 1 0 to 10 0 6 suggesting heterogeneous source materials involving both juvenile and ancient crust reworked crustal components based on the geological significance of granites at the southwestern margin of the north china plate the closure of the north qilian ocean occurred at 444 ma geochemical features suggest that the cataclastic syenogranite and granodiorite porphyry formed in an intraplate extensional and compressional setting respectively hence after a period of extensional post collisional intraplate evolution strong compressive forces affected the area

on the applicability of available regression models for estimating newmark displacements for low to moderate magnitude earthquakes the case of the betic cordillera s spain abstract newmark displacement estimation is generally computed using empirical models these models are estimated from large datasets that mainly comprise moderate to high magnitude events mw 6 0 in this work we study the performance of several of these models to study moderate to low magnitude scenarios for this purpose data from the betic cordillera s spain with magnitudes ranging from mw 3 5 to 6 3 were used to compare with model predictions the results show that errors in the estimates depend on the magnitude of events or on the yielding acceleration considered to estimate the displacement the availability of an appropriate range of data magnitude and yielding acceleration when defining the regression model may overcome the differences due to specific characteristics of the seismotectonic context of the area where data derives from the results also show that performance of models including several ground motion predictors is better than those based on a single parameter regardless of the combination these predictors furthermore regression models with polynomial forms present a better performance than other functions based on the logarithm of these predictors finally new specific models for the betic cordillera are proposed especially suitable for low magnitude events

geochemistry and origin of the intrusive hosts of the noril sk talnakhcu ni pge sulfide deposits the world class deposits of cu ni and platinum group elements pge of the noril sk talnakh district in russia are hosted by relatively small complex mafic ultramafic bodies that intrude permian sedimentary rocks and the lowermost suites of the siberian continental flood volcanic sequence the noril sk type ore bearing intrusions immediately overlie and are probably penecontemporaneous with weakly mineralized intrusions of the lower talnakh type which have similar petrological features but contrasting and much more variable nd os and sr isotopic compositions several types of spatially associated intrusions were emplaced after the ore bearing intrusions and the flood volcanic sequence to clarify relations between the various types of igneous bodies flood volcanic rocks noril sk type intrusions lower talnakh type intrusions and later intrusions and to help understand the formation of the ore deposits we undertook a detailed geochemical and nd os and sr isotopic study of eight of the more important intrusions the data indicate that these intrusions formed by the input of a series of magma pulses each of which produced rocks with distinctive petrology and chemical compositions these compositions are interpreted to have formed from mixtures of mantle derived magmas and different types of crustal rock which were encountered and assimilated during passage to the surface some of these variations may be superimposed on heterogeneities inherited from the mantle source the magmas that formed the lower talnakh type intrusions became contaminated with large amounts of crustal rock in a deep staging chamber the chemical and isotopic characteristics of the resultant hybrid magmas are broadly similar to those of basalts of the lower and middle nadezhdinsky lava subsuites nd 1 2 which are located about one third of the way through the overlying lava sequence these magmas became saturated in sulfur during contamination and segregation of sulfides resulted in the depletion of chalcophile elements recorded in the nd 1 2 lavas magmas feeding the ore bearing intrusions had trace element and isotopic compositions similar to those of the basalts in the upper two thirds of the volcanic sequence these magmas underwent lower degrees of contamination in a deep staging chamber and sulfur saturation was not reached these magmas therefore contained a full compliment of chalcophile elements when they encountered anhydrite rich sediments during passage toward the surface assimilation of these sediments led to the segregation of sulfides to form the ores two aspects of our data impose important constraints on the ore forming process the first is the os isotopic composition of the ore sulfides avg os 7 which is similar to that of mantle rocks and very different from those of sulfides that segregate from highly contaminated magma the second is the absence of ni depletion in olivine in rocks from the ore bearing intrusions most notably in the ore rich picritic gabbrodolerites the simplest explanation is that the sulfides segregated from magmas that were not highly contaminated and were transported into the intrusions by magmas different from those that yielded the sulfide if this explanation is correct it imposes some modifications to earlier models of sulfide ore deposition in the conduits of flood basalts

study on a failed dip slope with a thin sandy layer in 2004 niigata ken chuetsu earthquake among the extensive failed slopes in the 2004 niigata ken chuetsu earthquake japan a dip slope at yokowatashi ojiya was investigated intensively the sliding plane was along a weak thin tuff sandy layer which had been deeply weathered triaxial compression tests and plane strain compression tests were performed on undisturbed specimens obtained by block sampling and boring sampling to evaluate the strength that was mobilized on the sliding plane stability analysis based on the test results reveals that at normal time without earthquake and without an extremely high groundwater level the slope is stable furthermore the calculation of earthquake induced displacement provides a reasonable simulation of the failure of this slope

s saturation history of nain plutonic suite mafic intrusions origin of the voisey s bay ni cu co sulfide deposit labrador canada the voisey s bay deposit is hosted in a 1 34 ga intrusion composed of troctolite olivine gabbro and ferrogabbro the sulfide mineralization is associated with magmatic breccias that are enveloped by weakly mineralized olivine gabbros and troctolites and also occurs as veins along structures in adjacent paragneiss a dyke is connected to the base of the north wall of the eastern deeps intrusion and the entry point of this dyke into the chamber is the locus of the eastern deeps nickel sulfide deposit a detailed exploration in the area between the eastern deeps and the ovoid has shown that these intrusions and ore deposits are connected by a splayed dyke the eastern deeps deposit is surrounded by a halo of moderately to weakly mineralized variable textured troctolite vtt that reaches a maximum thickness above the axis of the eastern deeps deposit along the northern wall of the eastern deeps intrusion the massive sulfides and breccia sulfides are petrologically and chemically different when compared to the disseminated sulfides in the vtt and there is a marked break in ni tenor of sulfide between the two sulfides hosted in the dyke tend to have low metal tenors ni 100 2 5 3 5 sulfides in eastern deeps massive and breccia ores have intermediate ni tenors ni 100 3 5 4 and disseminated sulfides in overlying rocks have high ni tenors ni 100 4 8 four principal processes control the compositions of the voisey s bay sulfides coarse grained loop textured ores consisting of pyrrhotite crystals separated by chalcopyrite and pentlandite exhibit a two orders of magnitude variation in the pd ir ratio which is due to mineralogical variations where pentlandite is enriched in pd and ir is dispersed throughout the mineral assemblage a decrease in ir and rh from the margin of the ovoid toward cubanite rich parts at the central part of the ovoid is consistent with fractionation of the sulfide from the margins toward the center of the ovoid the ovoid ores have higher ni and pd tenor than the eastern deeps massive sulfides this is consistent with both a higher r factor and greater degree of silicate parental magma evolution in the ovoid than the eastern deeps the disseminated sulfides surrounding the eastern deeps deposit have some of the highest ni and pd tenors at voisey s bay which are indicative of not only more primitive magmas but also higher r factors than the ovoid or the eastern deeps vtt and normal textured troctolite of the eastern deeps that contain trace sulfide have 0 1 3 ppb pt and 0 1 3 ppb pd whereas weakly to heavily mineralized variable troctolites in the same unit have one to two orders of magnitude higher abundances of pt and pd troctolites and olivine gabbros from other parts of the voisey s bay intrusion and other nain plutonic suite intrusions including the kiglapait newark bay barth island mushua and nain bay south intrusion also have low platinum group element abundances although it is possible that this is a signature of a widespread sulfide saturation event that pre dated ore formation at voisey s bay it is more likely that platinum group element pge depletion is a product of the source melting process where low degrees of melting resulted in the retention of pge in the mantle source if so this indicates that pge depletion should be used with caution as an exploration tool in the nain plutonic suite

on far field occurrence of seismically induced landslides abstract earthquakes may induce landslides at large distances from the epicentral area in the last two decades there have been many studies of this phenomenon to determine the causes that contribute to the occurrence of landslides at very long distances from earthquake epicenter in this study which is based on previously published works a worldwide database comprising 270 earthquakes including 150 during the instrumental period was compiled to analyse the features of those landslides that occur at much further distances than maximum expected distances from the analysis of the compiled data it was observed that susceptible slopes can be grouped into five broad geological categories jointed rock marly clayey cohesive soils granular alluvial and or colluvial sediments volcanic soils and residual soil slopes these categories were equally likely to be associated with far field disrupted landslides whereas far field coherent landslides were more frequent on cohesive soil slopes other factors along with slope susceptibility may also contribute to far field landslides and increase the size of the area affected among these factors site effects antecedent rain and occurrence of seismic series have been cited the analysis of available data also showed that for events of the same magnitude far field disrupted landslides may occur at greater distances than coherent ones the same database has also been employed to determine for the first time the upper bound curves for the maximum observed epicentral distances of several types of landslides and the maximum area observed to be affected by landslides both based on the epicentral intensity of the events

nickel sulfide deposits in western australia a review the nickel sulfide deposits of western australia consist of many intrusive dunite associated and volcanic peridotite associated deposits of late archean age a few small gabbroid associated deposits of archean or proterozoic age and some other rare types some 96 percent of the nickel metal resource is contained in deposits concentrated in the curvilinear folded and strike faulted supracrustal belts of the eastern yilgarn block very magnesian ultramafic rocks and sulfidic metasediments abound in these belts which have commonly been metamorphosed to greenschist or lower amphibolite facies conditions major strike faults probably influenced the nature and distribution of volcanism and sedimentation later tectonometamorphic styles and nickel mineralization intrusive dunite associated deposits occur in semiconcordant lenses of peridotite to olivinite composition and of komatiitic affinities which are restricted to curvilinear zones 100 km or more long nickel sulfides occur centrally or marginally in the thickest part of the lens low grade 1 ni sulfides are abundant and enclose smaller bodies of higher grade disseminated and massive or breccia ores which may be in part tectonically displaced the ni content of the sulfide fraction is about 10 percent although low grade sulfides may be ni rich with ranges in ni cu of 19 to 70 and ni co of 30 to 70 the lenses may have been emplaced 1 passively as subvolcanic sills which fractionated olivine and sulfides and gave rise to associated komatiitic lavas and or 2 dynamically as dikelike bodies of sulfidic olivine rich crystal mush volcanic peridotite associated deposits are best developed at or near the base of volcanic komatiitic ultramafics occurring between metabasalts and at low stratigraphic levels in the succession there is little or no geographical coincidence between these deposits and the intrusive dunite associated deposits the ultramafics are mainly lavas ranging from picrite to olivine peridotite in composition with thicker and more magnesian flows dominating the lower mineralized part of the piles where thin interflow sulfidic metasediments are also common about 90 percent of the mineralization is at the base of the lowermost olivine peridotite flows which appear to be tongue shaped and to occupy original depressions in basalt surfaces devoid of sulfidic sediment thin discontinuous massive sulfides resting on metabasalt are overlain by thicker continuous and more extensive matrix to disseminated sulfides some massive and breccia ores are tectonically displaced the ni content of the sulfide fraction varies from 5 to 23 percent with an accompanying increase in ni cu from 10 to 16 and ni co from 40 to 65 on eruption of sulfidic komatiitic magma sulfide segregation under differential flow and gravity would probably result in the observed cross sections through the ore but with subsequent physical modification of the ore during metamorphism gabbroid associated deposits occur in layered or composite intrusions of gabbronorite with lesser pyroxenite peridotite and anorthosite which crystallized from basaltic magma of uncertain affinity the rocks are incompletely hydrated low grade disseminated or blebby sulfides form layers or irregular bodies associated with lenses or veins of matrix massive or breccia sulfides the ni content of the sulfide fraction is up to about 6 percent with a range of ni cu ratios of 1 to 7 and an ni co ratio average of about 25 the bulk chemistry of the intrusions and the sulfides and sulfide silicate textures are consistent with the existence of immiscible sulfide liquids at the magmatic stage layered sedimentary associated and vein type arsenical deposits are rare but indicate the possible involvement of nickel in volcanic exhalative and metamorphic hydrothermal processes respectively a complex history of weathering and supergene alteration has affected the deposits and presents major difficulties in exploration the recognition of siliceous limonitic cappings some with pseudomorphic textures led to the discovery of most deposits many problems remain before a more complete understanding of the genesis of the parental sulfidic magmas and their mode of ascent and emplacement into the crust is possible these are discussed with particular reference to the intrusive dunite and volcanic peridotite associated deposits which seem to be restricted to ca 2 7 b y old archean terrains worldwide

compositional variations of olivine and sulfur isotopes in the noril sk and talnakh intrusions siberia implications for ore forming processes in dynamic magma conduits olivine from the noril sk i main and northwestern talnakh ore bearing intrusions in the noril sk region occurs as inclusions discrete grains and poikilitic crystals the original compositions of olivine inclusions have been well preserved by their host oikocrysts from reaction with interstitial silicate and sulfide liquids in contrast the compositions of discrete and poikilitic olivine crystals have been variably modified by reequilibration with trapped silicate and sulfide liquids there are abrupt changes in the contents of nickel in olivine inclusions 500 1 500 ppm between different rock units in all three intrusions which indicates that the different rock units in these intrusions are not related to each other via in situ differentiation of a common parental magma but rather are consistent with separate pulses of magma with variable degrees of differentiation possibly involving olivine crystallization and assimilation of siliceous crustal material in a staging chamber the 34s values of the samples with high sulfur contents 800 ppm sulfur from all three ore bearing intrusions vary between 8 and 14 per mil two sulfur poor samples 600 ppm sulfur from the northwestern talnakh intrusion yield 34s values of 1 5 and 3 6 per mil these values are similar to the values of the sulfur poor rocks from the ore barren intrusions in the region and illustrate the fact that high sulfur contents couple with increasing 34s values such a relationship is consistent with the addition of crustally derived 34s enriched sulfur to the magma of the ore bearing intrusions in contrast to other models of sulfide segregation in closed systems we propose that sulfide segregation occurred in an open system and the magma involved was undersaturated in sulfur and undepleted in chalcophile elements we envision that the 34s enriched sulfur was introduced via circulating fluids that transported sulfur from evaporite in the underlying sedimentary sequence to the magma in a dynamic magma conduit the immiscible sulfide liquids that segregated during sulfur contamination settled down in the wider parts of the conduit as the magma continued to travel successive pulses of new magma entered the conduit reacted with the early sulfide and displaced much of the early magma in the conduit the ore bearing intrusions are thought to have crystallized within the wider parts of the conduits and their voluminous sulfide poor peripheral sills represent some if not all of the magma that flowed out of the conduits

foundation evaluation of underground metro rail station using geophysical and geotechnical investigations abstract excavations for underground space developments in a thickly populated urban area are sometimes hindered by unexpected formidable consequences like formation of sinkholes or uneven settlement of foundations such troublesome incidences occasionally damage structures in the vicinity of excavations although adequate design guidelines and codes of practices are adopted the disturbance of subsurface regime due to excavation or construction activities often leads to undesired stability issues with resultant appearance of weak zones the reinforcement of weak zones by grouting is one of the common remedies without demarcating the weak or the affected zones becomes counter productive excavation at a location in chennai mega city for metro rail was severely affected by soil piping with development of sinkholes and weakening of the surrounding strata subsequently development of cracks in the adjacent buildings and caused tilting of the nearby taller structures the mandated the geophysical and geotechnical investigations were carried out to demarcate the affected area to avoid further deterioration of the site cross hole seismic p and s wave velocities were estimated between10 pairs of boreholes up to 20 m depth on both the sides of the excavation two electrical resistivity tomography ert profiles each of 141 m in length were carried out in the same location cross hole s wave velocity profiles and resistivity tomograms clearly indicate the presence of weak zones and possible sinkhole locations site specific empirical relationship was established between s wave velocity and standard penetration test spt n value this relationship was further used for determination of spt n values from the measured vs values to compare the subsurface conditions identified under pre and post excavations the results confirmed the presence of weak zones which are responsible for the weakening of the surrounding strata in the foundation geophysical and geotechnical investigations similar to present investigation can be useful for designing metro rail projects in a subsurface environment comprising alluvium sand clay mixed with silt pebbles and boulders lying near a region of ground water pocket in a thickly populated urban area

the langmuir volcanic peridotite associated nickel deposits canadian equivalents of the western australian occurrences the 2 7 b y old abitibi greenstone belt is a crudely s shaped zone of metamorphosed volcanic subvolcanic and sedimentary rocks and associated intrusions through it are scattered a dozen small nickel deposits in volcanic peridotites their hosts are volcanic and subvolcanic ultramafic rocks typically containing 40 to 45 percent anhydrous mgo with spinifex tops and overlain by thinner peridotitic to pyroxenitic flows at least one deposit dumont is hosted by a dunitic intrusion others e g dundonald langmuir 2 are partially hosted in sulfidic iron formations mining of the langmuir 2 deposit permitted extensive underground mapping core logging and sample collecting the other deposits are known mainly from poor surface exposures and drill core the langmuir 1 and 2 deposits provided sufficient data to evaluate models for their origin and to compare them to nickel sulfide deposits associated with volcanic peridotites in western australia a magmatic origin is supported by the localization of the main ore zone in a paleotrough by the presence of a possible volcanic feeder beneath the ore and by the regular sequence through the basal ultramafic flow of massive ore overlain by net textured ore then by barren peridotite and lastly by a spinilex textured cap to the flow an unusual spinilex textured and sulfide bearing rock and skeletal chromite also support a magmatic origin as do the base and precious metal contents of the ores the high s se ratios averge 23 000 and slightly lower sulfur isotopic ratios average 0 5 per mil delta 34 s compared to most magmatic nickel sulfide deposits are similar to the ratios for windarra western australia and may be explained by assimilation of sulfide rich cherty iron formation other features incompatible with a purely maginatic origin include the presence of sheared and breccia ore and the high sulfur content of some ores these features result from deformation and greenschist facies metamorphism but surviving features of an earlier magmatic history argue against the ores being formed metamorphically evidence of contemporaneous fumarolic activity was found at the south end of the mine but its importance as an ore forming process was not supported by detailed petrological and geochemical studies limited data from the other deposits in the abitibi belt suggest a common origin for the langmuir deposits with minor variations attributable to the volume of ultramafic magma emplaced the volume of contained nickel sulfides the presence of sulfidic iron formations and the severity of alteration and metamorphism the deposits in western australia probably were formed by similar processes in particular the langmuir deposits display strikingly similar sulfide chemistries to the windarra deposits which are probably dae to assimilation of sulfide rich cherty iron formation