precambrian accretionary tectonics in the bou azzer el graara region anti atlas morocco ophiolites of the anti atlas of morocco occur as highly dismembered slivers of mafic and ultramafic rocks sandwiched between a precambrian craton and a magmatic arc tectonic slices of accretionary melange ophiolites and forearc basins have been juxtaposed by oblique subduction and transpression in the forearc region of a late proterozoic subduction zone synkinematic to postkinematic calc alkalic magmatism in these terranes indicates migration of the magmatic front over the deformed forearc terranes

pb isotopic evidence for an early enriched crust on mars abstract martian meteorite nwa 7533 is a regolith breccia that compositionally resembles the martian surface measured by orbiters and landers nwa 7533 contains monzonitic clasts that have zircon with u pb ages of 4 428 ga the pb isotopic compositions of plagioclase and alkali feldspars as well as u pb isotopic compositions of chlorapatite in the monzonitic clasts of nwa 7533 have been measured by secondary ion mass spectrometry sims the u pb isotopic compositions measured from the chlorapatite in nwa 7533 yield an age of 1 357 81 ga 2 the least radiogenic pb isotopic compositions measured in plagioclase and k feldspar lie within error of the 4 428 ga geochron these data indicate that the monzonitic clasts in nwa 7533 are a product of a differentiation history that includes residence in a reservoir that formed prior to 4 428 ga with a value 238 u 204 pb of at least 13 4 1 7 2 and a value 232 th 238 u of 4 3 this value is more than three times higher than any other documented martian reservoir these results indicate either the martian mantle is significantly more heterogeneous than previously thought value of 1 14 vs 1 5 and or the monzonitic clasts formed by the melting of martian crust with a value of at least 13 4 therefore nwa 7533 may contain the first isotopic evidence for an enriched differentiated crust on mars

geochemistry and origins of carbonate fluorapatite in seamount fe mn crusts from the pacific ocean abstract seamount phosphates are increasingly regarded as potential resources for rare earth elements ree and plus yttrium rey carbonate fluorapatite cfa formed within seamount ferromanganese fe mn crusts is the most common seamount phosphate mineral however reports on the mineralogy and geochemistry of cfa are few and thus its origin and acquisition of trace elements are not well understood in this study we analyzed the major and trace elements of cfa in fe mn crusts collected from western and central pacific seamounts to investigate the genesis of trace elements in the cfa this is the first study to use in situ analytical techniques such as electron microprobe analyzer epma and laser ablation inductively coupled plasma mass spectrometry la icp ms to analyze seamount cfa we found that the cfa hosts abundant minor and trace elements and propose that ionic substitutions are responsible for the high contents of so3 sio2 rey sr na fe and mn in the cfa veins found in the fe mn crusts i e sio32 and so42 substitute for po42 while ree3 y3 na fe2 and mn2 substitute for ca2 ree3 substitutions for ca2 in the cfa are charge compensated by na substitution for ca2 fourier transform infrared spectroscopy ftir analysis shows that co32 mainly substitutes for po42 in the cfa crystal structure and there is a minor substitution of po42 by co3f3 ocean water is the major source of the p and rey which when precipitated as seamount cfa is characterized by high ree 345 to 6016 ppm and heavy ree hree enrichments monazite grains dispersed in the seamount cfa contribute trace amount of rey these results shed light on the composition and element mobility of seamount cfa with economic potential which also provides valuable insights into global ocean chemical cycling e g ree

a branched magma feeder system during the 1669 eruption of mt etna evidence from a time integrated study of zoned olivine phenocryst populations the 1669 eruption of mt etna was one of the most voluminous and devastating of its flank eruptions in historical times despite a large body of relevant research knowledge of the timing and duration of magma transfer and magma recharge through the internal plumbing system preceding and during the eruption is still limited to address that lack of knowledge we apply a three way integrated method linking systems analysis of crystals a time integrated study of zoned olivine populations and a forward modelling approach using thermodynamic calculations analysis of 202 olivine crystals erupted during the initial pre march 20 i e set1 and the final post march 20 i e set2 and mtrs stages of the eruption reveals the existence of three magmatic environments mes in which the majority of the olivine cores m 1 fo 75 78 and rims i e m 5 fo 51 59 and m 3 fo 65 69 formed application of the rhyolite melts software allowed us to constrain the key intensive variables associated with these mes we find that temperature water content and oxidation state vary between these mes application of diffusion modelling to the zoned olivine crystals allowed us to reconstruct the timing and chronology of melt and crystal transfer prior to and during the 1669 flank eruption we find that following the formation of the olivine cores m 1 fo 75 78 the reservoir m 1 was intruded by batches of more evolved degassed and possibly aphyric m 5 type magma commencing 1 center dot 5 years prior to eruptive activity this is the origin of the set1 olivine rims i e fo 51 59 in the months prior to eruption timescale data show that recharge activity along the newly established pathway m 1 m 5 increased notably starting in november 1668 only a few weeks after the first intrusive episode into the m 1 reservoir a second pulse of magma injections m 3 type magma occurred and a new pathway m 1 m 3 opened this is how the set2 olivine rims i e fo 65 69 formed for several weeks a bifurcated transport system with two dominant magma pathways developed along m 1 m 5 and m 1 m 3 dyke injections accompanied by vigorous seismicity in the days immediately before eruption the local magma transfer dynamics changed and the m 1 m 5 recharge activity slowed down as shown by a relative lack of crystals recording shorter timescales m 1 m 3 recharge however remained high and persisted following the eruption onset on march 11 during which the set1 lavas were drained we propose that the change of the local magma transfer dynamics might be linked to changes in the local stress field brought on during eruption this may potentially have been due to repeated dyke injections into etna s shallow plumbing system disrupting the early m 1 m 5 pathway and at the same time stabilizing the m 1 m 3 route as a dominant feeder this transfer of system feeding would reproduce the observed syn eruptive recharge and mixing in the weeks following eruption onset culminating in the eruption of the later set2 lavas

anti atlas morocco role in neoproterozoic western gondwana reconstruction abstract reconstruction of latest neoproterozoic gondwana hinges on the interpretation of the subduction and collision kinematics of pan african orogenic belts that rim the west african craton the anti atlas suture zone of southern morocco has presented an enigma in this reconstruction as the inferred subduction zone polarity and age of suturing appear to be incongruous with better known west african orogens to the west mauretanian bassaride and rokelide and transaharan orogens to the east ougarta tuareg gourma and dahomeyan contrary to previous interpretations new data from the anti atlas indicate a history of late neoproterozoic 750 600 north dipping subduction culminating in the 600 ma collision of the saghro magmatic arc to the north with the north facing rifted margin of the west african craton thus the anti atlas suture links a 6000 km long chain of pan african suture zones that essentially encircle the west african craton the suture zones demarcate the former position of subduction zones that in all cases dipped away from the west african craton the anti atlas suture links the western and eastern segments of the pan african orogenic belts associated with the amalgamation of western gondwana

the effect of mole drainage on the hydrological response of a swelling clay soil abstract the results of a plot experiment to determine the effects of mole drainage on the hydrological response of a swelling clay soil under pasture are described it is shown that the response is very dependent on antecedent moisture conditions and that higher peak flows may be generated under relatively dry conditions on the drier drained plot this appears to be related to the generation of flows in interpedal macropores supplying water to the mole drains under wet conditions the hydraulic efficiency of the macropores is reduced by swelling of the clay and surface saturation develops on the undrained plot this results in generally higher peak discharges than from the drained plot recession discharges and total water yields are almost always higher from the drained plot the implications of this work are that it may be very difficult to detect or model the influence of clay land drainage on river flows

hillslope run off thresholds with shrink swell clay soils irrigation experiments on 12 instrumented field plots were used to assess the impact of dynamic soil crack networks on infiltration and run off during applications of intensity similar to a heavy rainstorm water was seen being preferentially delivered within the soil profile however run off was not observed until soil water content of the profile reached field capacity and the apertures of surface connected cracks had closed 60 electrical resistivity measurements suggested that subsurface cracks persisted and enhanced lateral transport even in wet conditions likewise single ring infiltration measurements taken before and after irrigation indicated that infiltration remained an important component of the water budget at high soil water content values despite apparent surface sealing overall although the wetting and sealing of the soil profile showed considerable complexity an emergent property at the hillslope scale was observed all of the plots demonstrated a strikingly similar threshold run off response to the cumulative precipitation amount copyright 2014 john wiley sons ltd

improved spatial resolution of elemental maps through inversion of la icp ms data laser ablation inductively coupled plasma mass spectrometry la icp ms provides the spatial distribution of elements within crystals and therefore can constrain the rates of geological processes spatial resolution of la icp ms is limited by the requirement to ablate sufficient material to surpass the detection limit of the instrument too little material and the concentration cannot be measured too much material from the same spatial location and the possibility of depth dependent variations in concentration increases because of this requirement and typical analytical setup this commonly places a lower bound on the diameter of an ablation spot size of approximately 20 m for elements with ppm concentration here we present a means to achieve sub spot size resolution using inverse methods we discretize the space sampled in an analysis into pixels and note that the average concentration of the pixels sampled by a spot equals the measured concentration as multiple overlapping spots sample some of the same pixels we can combine discrete expressions for each spot as a system of linear equations through linear inversion with smoothness constraints we can solve for unknown pixel concentrations we highlight this approach with two natural examples in which diffusive processes are important magmatic ascent speeds and u th he noble gas thermochronometry in these examples accurate results require that the true concentration gradients can be recovered from la icp ms data we show that the ability to infer rapid rates of magma ascent is improved from months to weeks and that we are able to interpret previously un interpretable thermochronometric data

crystal recycling in the steady state system of the active stromboli volcano a 2 5 ka story inferred from in situ sr isotope and trace element data in situ sr isotope data by microdrilling coupled with major and trace element analyses have been performed on plagioclase and clinopyroxene from seven samples collected during the 2002 2003 eruptive crisis at stromboli volcano aeolian islands italy on 28 december 2002 the persistent moderate explosive activity was broken by an effusive event lasting about 7 months a more violent explosion paroxysm occurred on 5 april 2003 two magma types were erupted namely a volatile poor and highly porphyritic magma hp magma poured out as scoria or lava and a volatile rich phenocryst poor magma lp magma found as pumice lp magma differs from the hp magma also for its slightly less evolved chemistry the groundmass composition and the lower sr isotope ratios micro sr isotope data show the presence of zoned minerals in strong isotope disequilibrium as previously found in products erupted in 1984 1985 and 1996 ad with 87sr 86sr values generally decreasing from cores to rims of minerals only some outer rims testify for equilibrium with the host groundmass the internal mineral zones with high sr isotope ratios 0 70665 0 70618 are interpreted as antecrysts crystallised during the previous activity and recycled in the present day system since the opening shoshonitic activity of the recent period which occurred at about 2 5 ka ago this result has implications for the dynamics of the present day plumbing system of stromboli at intermediate pressure about 2 3 km depth and allows us to propose a model whereby an hp magma reservoir is directly interconnected at the bottom with a cumulate crystal much reservoir efficient mixing between residing hp and input lp magmas can occur in this reservoir due to more similar rheological characteristics of the two magmas than in the conduit where crystallisation is enhanced by degassing antecrysts and possibly melts re enter in the hp magma reservoir both from the bottom recycled by ascending lp magmas crossing the crystal mush and from the top recycled by descending degassed and dense hp magma residual of the periodic strombolian explosions at the surface the isotope variation measured in the groundmasses allows calculating the proportion of the lp magma entering the shallow hp magma reservoir at 20 from this proportion we estimate that the total volume of lp magma input during 2002 2003 closely matches the magma volume erupted in the effusive event suggesting a steady state system at broadly constant volume the comparison with estimates of the lp magma volume ejected by the paroxysm indicates that the lp magma amount directly reaching the surface during the 5 april paroxysm is minimal with respect to that entering the system

deep massive sulphide exploration using 2d and 3d geoelectrical and induced polarization data in skellefte mining district northern sweden geoelectrical and induced polarization data from measurements along three profiles and from one 3d survey are acquired and processed in the central skellefte district northern sweden the data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1 5 km the 2009 data were inverted previously and their joint interpretation with potential field data indicated several anomalous zones the 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area several high chargeability low resistivity zones interpreted as possible massive sulphide mineralization and associated hydrothermal alteration are revealed the 3d survey data provide a detailed high resolution image of the top 450 m of the upper crust around the maurliden east north and central deposits several anomalies are interpreted as new potential prospects in the maurliden area which are mainly concentrated in the central conductive zone in addition the contact relationship between themajor geological units e g the contact between the skellefte group and the j orn intrusive complex is better understood with the help of 2010 deep resistivity chargeability data the bottommost part of the vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to 1 km depth

trace element mapping by la icp ms assessing geochemical mobility in garnet a persistent problem in the study of garnet geochemistry is that the consideration of major elements alone excludes a wealth of information preserved by trace elements particularly the rare earth elements rees this is despite the fact that trace elements are generally less vulnerable to diffusive resetting and are sensitive to a broader spectrum of geochemical interactions involving the entire mineral assemblage including the growth and or dissolution of accessory minerals we outline a technique for the routine acquisition of high resolution 2d trace element maps by la icp ms and introduce an extension of the software package xmaptools for rapid processing of la icp ms data to visualise and interpret compositional zoning patterns these methods form the basis for investigating the mechanisms controlling geochemical mobility in garnet which are argued to be largely dependent on the interplay between element fractionation mineral reactions and partitioning and the length scales of intergranular transport samples from the peaked hill shear zone reynolds range central australia exhibit contrasting trace element distributions that can be linked to a detailed sequence of growth and dissolution events trace element mapping is thus employed to place garnet evolution in a specific paragenetic context and derive absolute age information by integration with existing u pb monazite and sm nd garnet geochronology ultimately the remarkable preservation of original growth zoning and its subtle modification by subsequent re equilibration is used to see through multiple superimposed events thereby revealing a previously obscure petrological and temporal record of metamorphism metasomatism and deformation

the nature of the tile drain outfall hydrograph in heavy clay soils abstract the outfall hydrographs of agricultural underdrainage installations in a heavy clay soil are examined over four drainage seasons seasonal differences in drainage response to rainfall are attributed to antecedent soil conditions and these are controlled in part by the influence of topography upon downslope seepage bowl shaped landforms are kept moister by convergent interflow streamlines and drainage follows the onset of rainfall most quickly in winter well drained convex slopes on the other hand are subject to greater summer desiccation and deep cracks convey autumn rainwater directly into the subsoil so that drainage response here is quicker at this time of year peak drain flow occurs at 3 6 hr after the rainfall centroid in winter for both topographical situations but median values of peak discharge can be up to four times those of the non winter drainage period during which absorption of rainfall by the soil leads to a reduction in drainage outfall the largest risk of flooding in river basins where under drainage is widespread comes from complex storms secondary peaks in the drainage hydrograph not only arrive earlier by an average of 1 38 hr but are also shown to reach discharges more than three times those associated with simple storms having equivalent rainfalls

diffusion coupling between trace and major elements and a model for calculation of magma residence times using plagioclase residence times of plagioclase crystals in magma reservoirs can be determined by modeling the compositional zoning of trace elements in these crystals we present a formulation to model diffusion of trace elements in plagioclase paying special attention to certain thermodynamic and kinetic aspects in particular we account for the compositional dependence on anorthite content of the chemical potential and diffusion coefficients of trace elements e g mg the choice of suitable boundary conditions and potential effects of diffusion in more than one dimension we show that contrary to intuition diffusive fluxes of trace elements may be coupled to major element concentration gradients and ignoring such coupling can lead to incorrect estimates of timescales we illustrate application of the model using plagioclase crystals from a suite of gabbroic xenoliths from a holocene dacitic lava flow of volcan san pedro chilean andes 36 s the inferred timescale for metasomatism of the xenoliths by evolved liquids is on the order of 100 30 to 148 yr and serves to illustrate how trace element zoning in plagioclase provides a window into timescales of magmatic processes inaccessible by isotopic or other methods

a pilot study to test the reliability of the ert method in the identification of mixed sulphides bearing dykes the example of sidi flah mine anti atlas morocco abstract a multidisciplinary study comprising geological petrographical and geophysical methods was carried out for the identification and the geometrical and volumetric assess of the main mineralized bodies mixed sulphides zn pb and fe cu in the area of the anti atlas chain located at sw of the town of sidi flah ouarzazate morocco the initial phase of exploration involved an extensive fieldwork structural investigations and sampling and a detailed survey for verifying the effectiveness and reliability of the electrical resistivity method ert geological fieldworks and laboratory analyses played a fundamental role in identifying the resistivity anomalies and constraining tomographic results main issues we focused on are i mineralized bodies imaging according to the electrodic step ii consistency with geometry of mineralized bodies iii contrast of electrical resistivity between mineralized dykes and host rocks iv possible correlations between the type and amount of sulphides and electrical resistivity

titaniq a titanium in quartz geothermometer titanium is one of many trace elements to substitute for silicon in the mineral quartz here we describe the temperature dependence of that substitution in the form of a new geothermometer to calibrate the titaniq thermometer we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt at temperatures ranging from 600 to 1 000 c at 1 0 gpa the ti contents of quartz in ppm by weight from 13 experiments increase exponentially with reciprocal t as described by text log left x text qtz text ti right 5 69 pm 0 02 frac 3765 pm 24 t k application of this thermometer is straightforward typically requiring analysis of only one phase quartz this can be accomplished either by epma for crystallization temperatures above 600 c or by sims for temperatures down to at least 400 resulting temperature estimates are very precise usually better than 5 c potentially allowing detailed characterization of thermal histories within individual quartz grains although calibrated for quartz crystallized in the presence of rutile the thermometer can also be applied to rutile absent systems if tio2 activity is constrained

age of the cretaceous alkaline magmatism in northeast iberia implications for the alpine cycle in the pyrenees cretaceous magmatism in northeast iberia is related to the opening of the bay of biscay and counterclockwise rotation of iberia with respect to europe and predates the collision between iberia and europe that resulted in the formation of the pyrenees to better constrain the age of this magmatism we have undertaken a ar ar study on samples from the pyrenees and the catalonian coastal ranges in the basque cantabrian basin and the north pyrenean basins we have obtained albian ages ca 102 ma in the northern catalonian coastal ranges we have obtained campanian ages ca 79 ma we integrate our data with a review of previously published ages and discuss our results in terms of their geodynamic significance the cretaceous magmatism in the pyrenees is albian santonian mostly occurring between 105 to 85 ma and was emplaced in a tectonically unclear context after the opening of the bay of biscay and rotation of iberia the magmatism in the catalonian coastal ranges is well constrained to ca 79 ma and could mark the onset of alpine shortening in the pyrenean realm in northeasternmost iberia finally we describe a late triassic ca 232 ma early jurassic ca 180 ma phase of magmatism in the central pyrenees previously considered to be cretaceous that widens temporally and geographically the extent of the rift related alkaline magmatism in southwestern europe at that time key points new ar ar data update the age of the cretaceous magmatism in ne iberia magmatism in the pyrenees postdates the rotation of iberia magmatism in the catalonian coastal ranges could mark the onset of alpine shortening

trace element diffusion in jadeite and diopside melts at high pressures and its geochemical implication abstract diffusivities of geochemically important trace elements eleven rare earth elements ree rb sr ba and y in jadeite and diopside melts and those of zr nb th and u in jadeite melt have been measured at pressures between 7 5 and 20 kbar and at temperatures 50 200 above the liquidus using diffusion couples and ion microprobe analysis the concentrations of these elements in the experimental charges are close to those in natural igneous rocks in the jadeite melt which is nearly fully polymerized nbo t 0 1 diffusivities of ree increase with increasing ionic radii 2 diffusivities of tri and tetravalent elements increase with increasing pressure at constant temperature whereas those of mono and divalent elements do not change significantly with pressure and 3 diffusivities of these elements decrease with increasing their ionic charge at constant pressure and temperature in the diopside melt which is considerably less polymerized nbo t 2 1 diffusivities of these trace elements depend mainly on their ionic radii rather than ionic charges the diffusivities of mono and divalent ions decrease with increasing ionic radii at constant pressure and temperature and 2 diffusivities of ree are nearly the same as that of ca and decrease with increasing pressure at constant temperature the behavior of these trace elements is correlated with that of major elements in the jadeite melt tri and tetravalent elements behave similarly to network forming cations al and si whereas mono and divalent elements behave as network modifying cations similarly to na in the diopside melt the diffusion behavior of all these trace elements is similar to that of network modifying cations ca and mg the results of the present experiments suggest that the abundance of some trace elements in igneous rocks may have been affected by diffusion process at the magmatic stage in the case of ree for example if two different magmas with high and low ree concentrations become in contact one another by multiple intrusion and a zoned magma chamber is formed diffusion begins to take place between them and near the interface the ree enriched magma will become more light ree depleted whereas ree depleted magma will become more light ree enriched and in addition if magmas are reduced the former will show a negative eu anomaly whereas the latter will show a positive eu anomaly

assessment of subsurface lithology in mountain environments using 2d resistivity imaging abstract the use of 2d resistivity imaging for the investigation of typical periglacial phenomena is shown on different case studies from a mid latitude high alpine and a high latitude subarctic periglacial environment important parameters that need to be determined for geomorphological studies in mountain environments are the location and extent of permafrost and its characteristics the spatial variability of the active layer as well as the internal structure of different periglacial landforms the investigations on different typical periglacial features demonstrate that 2d electrical resistivity imaging is a suitable method to detect permafrost with an appropriate accuracy delineation of active layer thickness is possible but depends on the contrast in resistivity between the active layer and the permafrost underneath the detection of small scale variability within the internal structure of some typical periglacial landforms can be limited because of the smoothing effect of the wenner array and the high ground resistances and weak signal strength which do not allow the successful application of the dipole dipole array hence limitations of application of geoelectric methods can arise from the rugged terrain conditions in periglacial mountain environments since good electrical coupling between the electrodes and the ground is a prerequisite for geoelectrical surveys nevertheless it is demonstrated that even on rough terrain conditions 2d electrical resistivity imaging could be used successfully to obtain reproducible results which are required to use changes in the apparent resistivity measurements to monitor changes in the subsurface resistivity distribution and hence permafrost aggradation and degradation

proterozoic blueschist bearing melange in the anti atlas mountains morocco abstract blueschists from the bou azzer inlier provide compelling evidence for late proterozoic subduction in the anti atlas mountains of morocco high pressure low temperature metabasites containing blue amphibole minerals crossite and magnesioriebeckite record pressures in excess of 5 kbar together with regional relationships the geologic setting of the blueschists constrains the polarity of pan african subduction in this region which occurred from 750 to 600 ma blueschist facies rocks crop out in a heterogeneous assemblage of variably deformed and metamorphosed tectonic slices of ophiolitic fragments enclosed in a schistose serpentinite matrix the melange belt containing the blueschist facies rocks is intruded by a number of diorite plutons one of which has yielded a u pb radiometric age of 650 ma together with transaharan belt to the southeast the anti atlas suture zone exposed within the bou azzer inlier contains among the oldest known blueschist bearing ophiolitic melanges in the world

variations in the hydrology of an underdrained clay hillslope abstract this paper presents evidence for the existence of the hydrological routes by which rainfall moves to the drainage system through clay soil at wytham in oxfordshire uk focusing particularly on the hydrology of the a horizon tile drain discharge was continuously monitored at the site and piezometer and tensiometer arrays were installed over the hillslope in order to study the spatial variations in hydrological response to rainfall a combination of dye tracing ring and tension infiltrometry was used to determine the variations in infiltration capacity over the hillslope and to characterise macropore flow the study established that both lateral and vertical macropore flow through inter pedal cracks are an important component of the hydrology of an underdrained site two regions of macropore discontinuity were identified in the soil profile at the base of the rotovated layer and at the base of the a horizon saturated layers developed at both these locations during rainfall over the winter a surface seal developed at the base of the hillslope tension infiltrometer measurements suggested that once the soil surface was sealed earthworm burrows of 6 mm diameter were responsible for up to 86 of the vertical infiltration into the a horizon temporal variations in hydrological characteristics were noted due to the swelling of the clay soil as it wetted up during the autumn and winter period lateral flow took place by a combination of macropore and preferential routes in saturated regions within the a horizon during periods of winter drainflow lateral macropore flow in the top 10 cm of the soil was the most important lateral route for water and was initiated by a critical pore water pressure of 0 3 kpa deeper lateral flow was limited and occurred predominantly through the soil matrix during autumn drainflow however inter pedal cracks were well developed through the a horizon and lateral flow at the base of the a horizon was dominant

post variscan tectonics in eastern anti atlas morocco new field data integrated by fission track ft analysis unravel an innovative scenario for the post variscan evolution of the eastern anti atlas this area unaffected by meso cenozoic tectonics according to most workers is crosscut by crustal faults bearing evidence of a polyphase deformation history apatite ft ages ranging between 284 and 88 ma point to fast neogene exhumation and unravel contrasting cooling paths across major faults results show that the study area was buried beneath 2 km of allochthonous variscan units now eroded the eastern anti atlas acted as the southern shoulder of the atlasic rift in the mesozoic and underwent a dextral transpressional structuring of neogene age followed by sub meridian shortening the southern front of atlasic deformation is therefore located inside the anti atlas region and it is still active

decadal time gaps between mafic intrusion and silicic eruption obtained from chemical zoning patterns in olivine abstract intrusion of mafic magma in a silicic crustal reservoir has been reported in numerous studies of subduction related volcanoes and is considered a main process for triggering explosive eruptions and for transferring geochemical signatures from the mantle to the crust here we determine the timescales between mafic silicic encounters and eruption by exploiting the fact that during such interactions magmas exchange crystals and their mineral compositions will strive to equilibrate to the new environmental conditions specifically we model the fe mg zoning patterns of olivine found in the dacites andesite and quenched mafic inclusions of the holocene zoned eruption of volcan san pedro 36 s chilean andes the san pedro eruption is an example where mixing between silicic and mafic magmas produced intermediate compositions e g andesite at depth in the magma reservoir for modeling the compositional profiles we took into account the anisotropy of fe mg diffusion in olivine and also the effects of diffusion in multiple dimensions aspects that have been largely neglected in previous works the retrieved timescales for olivine melt equilibration by diffusion display an array ranging from 1 year for the most silica rich dacite to 50 years for the andesite this array of timescales rather than a single value provides new insight into the details of mafic silicic mixing at depth they reveal processes that occur on a longer timescale than the days to weeks time gap for cases where the mafic intrusion triggered the eruption and they might be associated with the instances where seismic activity or significant inflation of the volcanic edifice was not immediately followed by eruption on the other hand the year to decade timescales that we report for producing magmas of intermediate composition e g andesites are much shorter than the 10 3 10 5 years inferred from u series disequilibria data for igneous differentiation by closed system fractionation to produce similar magma compositions at subduction zones

electrical and magnetic properties of sulfides the metal sulfides exhibit a great diversity of electrical and magnetic properties with both scientific interest and practical applications these properties apply major constraints on models of the electronic structure or chemical bonding in sulfides vaughan and rosso 2006 this volume the pure and doped synthetic equivalents of certain sulfide minerals have actual or potential applications in the electronics industries optical devices photovoltaics photodiodes and magnetic recording devices sulfides are also components of many thin film devices and have been extensively investigated as part of the nanotechnology revolution certain electrical and magnetic properties of sulfide minerals mean they contribute to geomagnetism and paleo magnetism and provide the geophysical prospector with exploration tools for metalliferous ore deposits to the mineral technologist these same properties provide methods for the separation of the metal bearing sulfides from associated waste minerals after mining and milling and before extraction of the metal by pyrometallurgical or hydrometallurgical treatment in this chapter the theory and measurement of electrical and magnetic properties are outlined along with spectroscopic and diffraction studies that can provide insights into magnetic behavior are discussed a brief review of electrical and magnetic studies of major sulfide minerals includes some examples of the applications of sulfide electrical and magnetic properties including special consideration of the properties of sulfide nanoparticles most of the available data presented are for pure synthetic binary and ternary sulfides as very small concentrations of impurities can dramatically affect electrical properties leading to problems of interpreting data from natural samples although data for several of the commonly found sulfides are discussed in this chapter no attempt is made at a comprehensive coverage the section below on theory and measurement of electrical and magnetic properties draws on the account given in vaughan and craig 1978 to which readers are referred for further details it

mineral textures and zoning as evidence for open system processes investigations of mineral textures and zoning as evidence for open system processes during magmatic evolution have always been a centerpiece of petrological studies and have provided some of the best evidence for magma mixing and crustal contamination for many decades e g milch 1905 kuno 1936 eichelberger 1975 sato 1975 anderson 1976 in fact evidence from mineral studies was instrumental in the acceptance of magma mixing as important petrological process ever since it was initially proposed by bunsen 1851 in recent years mineral studies are invigorated by the development of high precision high resolution analytical instruments and techniques through which textural information and compositional data are combined e g jerram and davidson 2007 as minerals respond texturally and compositionally to changing magmatic environments they preserve in their crystal growth stratigraphy a wealth of information regarding their past history of magmatic processes and compositions cf ginibre et al 2007 on the other hand magmatic liquids melts are snapshots of current magmatic states and provide less direct evidence of the processes responsible for their evolution in addition liquids may crystallize thereby destroying the direct evidence they provide with an appropriate set of observations and measurements we can correlate textures with mineral compositions and thus produce a richer composite picture of magmatic evolution than compositional data of minerals alone this contribution reviews the zoning and textures of minerals frequently encountered in volcanic rocks many of which apply equally to plutonic rocks and the interpretations ascribed to these features in terms of open system magmatic processes first i will address the analytical tools that are used to acquire textural and compositional data followed by a brief review of open system processes and a summary of the relevant textures from that point on i will address some mineral specific aspects followed by a discussion

preferential eruption of andesitic magmas through recharge filtering at subduction zones andesite lavas erupt in greater abundance than the individual magmas that mix to produce them textural and geochemical analyses of andesites from mount hood oregon reveal that injection and mixing of iron and magnesium rich magma in the magma chamber can initiate the volcanic eruption andesitic volcanic rocks are common in subduction zones and are argued to play an important role in the formation and evolution of the continental crust at convergent margins1 2 3 4 andesite formation is dominated by mixing between iron and magnesium rich mafic magmas and silica rich felsic magmas1 2 4 the abundance of andesites in many subduction zones suggests they erupt in preference to the magmas that mix to produce them4 however the reasons for this remain unclear here we use textural and geochemical analyses of andesites from mount hood oregon to show that eruptions are closely linked with episodes of mafic recharge the intrusion of mafic magma into a shallow felsic magma reservoir the felsic and mafic magmas involved rarely erupt by themselves probably because the former are too viscous and the latter too dense mafic recharge overcomes these barriers to eruption and as it also promotes efficient mixing results in preferential eruption of mixed andesitic magmas the abundance of andesites therefore relates to local crustal conditions and the ability of magmas to erupt we suggest that volcanoes such as mount hood that erupt homogeneous andesitic compositions through time are those that are the most reliant on mafic recharge to initiate eruptions

the effect of intra crystal uranium zonation on apatite u pb thermochronology a combined id tims and la mc icp ms study abstract quantitative reconstruction of high temperature thermal histories 350 c has applications in metamorphic studies processes which exhume deep crust the evolution of active margins over hundreds of millions of years and the study of extra terrestrial rocks previous studies have demonstrated that apatite u pb data can be used to recover thermal history information at t 350 c from single crystal bulk dates we present u pb bulk grain id tims and intra grain la mc icp ms u pb data from apatites to evaluate the importance of parent isotope u distribution when extracting thermal history information from apatites that have experienced partial pb loss we find that parent u zonation can cause considerable scatter when single bulk grain dates are compared with their grain size and therefore u zonation must be taken into account when inverting u pb dates and grain sizes to seek thermal history solutions we show that accurate thermal history solutions can be obtained from apatites which have zoned concentrations when in situ variations in u concentration and u pb dates are modelled this observation validates the hypothesis that pb is lost by thermally driven volume diffusion in situ analytical techniques yield significantly more accurate thermal history solutions than bulk grain id tims analyses when investigating rocks which contain compositionally zoned apatites

nanoscale characterisation of crystal zoning abstract advances in analytical techniques are fundamental to the enhanced understandings of many geological processes zoned volcanic crystals have been analysed by low 5 kv field emission gun electron probe micro analyser feg epma and nanosims to obtain sub micrometre chemical profiles and compared to time of flight sims tof sims and high 15 20 kv epma profiles plagioclase and orthopyroxene crystals have been analysed by feg epma at accelerating voltages of 5 kv providing a spatial resolution step size of 350 nm the resolution of the lowest energy x ray for orthopyroxene crystals using a 30 nm beam and ca 750 nm for plagioclase crystals which at low voltages are unstable and require a 500 nm defocused beam step sizes are comparable in size to interaction volumes analytical protocols are detailed that permit quantitative major and minor element compositions to be acquired at similar precision and accuracy as traditional epma analyses at 15 20 kv nanosims analysis of the same crystals provides a greater spatial resolution of up to 200 nm and allows the measurement of li also the nanosims profiles however cannot currently be quantified the ability to analyse crystals at sub micrometre scales is demonstrated by the good agreement between nanosims feg epma conventional epma and tof sims data feg epma nanosims and tof sims techniques have broad applications within the earth sciences in petrologic studies for example these methods have the ability to analyse small crystals in experimental charges and provide chemical profiles of crystal zoning at a spatial resolution of ca 200 300 nm such profiles are important in crystal forensics and diffusion chronometry studies the implications for the latter application are that timescales of volcanic processes that occur in the days years immediately prior to the eruption can now be studied

synthetic model testing and distributed acquisition dc resistivity results over an unconformity uranium target from the athabasca basin northern saskatchewan the dc resistivity method has become a preferred reconnaissance mapping tool for uranium exploration targets in the athabasca basin in northern saskatchewan canada regionally uranium deposits can occur beneath 1 km thick sandstone cover rocks are commonly associated with deeper basement graphitic metasedimentary units and are also often accompanied by clay alteration zones in the sandstones as a result deep penetrating electromagnetic and electrical geophysical techniques are ideally suited for indirect exploration of these types of deposits a variety of electrode configurations are being used however the pole pole array is currently favoured in the athabasca basin due to its high signal levels its deep penetration and its anomaly resolution more recently however other technologies such as audio magnetotellurics amt mt and 24 bit a d distributed acquisition systems das have been introduced to extend the depth of exploration below 1 km in the example presented here a das acquisition system was used to acquire dc resistivity data using a variety of electrode arrays to examine the response parameters from the different configurations along a single line located along a known conductive trend at the m zone on the wheeler river property

the moroccan anti atlas the west african craton passive margin with limited pan african activity implications for the northern limit of the craton abstract the moroccan anti atlas region located south of the south atlas fault has been viewed traditionally as containing two segments separated by the anti atlas major fault these two segments are said to consist of a 600 700 ma pan african segment located in the northeast and b 2 ga eburnian segment situated to the southwest on the basis of observations in the zenaga and saghro inliers and of a recent literature review we suggest that this subdivision is inappropriate in that eburnian and pan african materials occur throughout the anti atlas region the entire anti atlas is underlain by eburnian crust unconformably overlain by a lower neoproterozoic passive margin allochthonous pan african ocean crustal slices were thrust onto the west african craton wac passive margin sequence 685 ma ago as a result of pan african accretion tectonics high level high k calc alkaline and alkaline granitoids locally intruded the anti atlas sequence as a whole at the end of the pan african orogeny at 585 560 ma the intervening 100 m y interval was marked by quiescence this succession of events can be related to the behaviour of one single rigid cratonic passive margin during an orogeny and correlated to the pan african events that occurred to the east in the tuareg shield and to the north in avalonian terranes this model implies that the actual northern limit of the wac is located at the south atlas fault saf and not at the anti atlas major fault aamf we propose that the aamf corresponds to the southwestern boundary of an aulacogen that formed along the northern margin of the wac during early neoproterozoic times this is consistent with the development of the gourma aulacogen on the eastern side of the wac this model further suggests that the northeastern boundary of the wac occurs north and not south of ougarta algeria support for this model is provided by geological and geophysical evidence

the moroccan anti atlas the west african craton passive margin with limited pan african activity implications for the northern limit of the craton since 1980 several diverging models for the pan african fold belt of the anti atlas mountains have been proposed differences mainly result from diverging interpretations of geological geochemical and geochronological data however the fundamental point is the lack of a detailed lithostratigraphic framework of the neoproterozoic successions supported by geochronological data and regional correlations furthermore these models did not evolve from multidisciplinary studies which are essential in the case of this belt whose structure is complex and diversified we discuss here some points taken as a base by ennih and liegeois to conclude that the entire anti atlas is underlain by eburnian crust and that the northern limit of the west african craton wac and its passive margin is located at the south atlas fault saf this led the authors to propose a new model of the anti atlas belt which also explains the origin of the khzama bouazzer ophiolite 1 evidence for a palaeoproterozoic basement in saghro

water movement and isoproturon behaviour in a drained heavy clay soil 1 preferential flow processes abstract the processes and mechanisms that control pesticide transport from drained heavy clay catchments are being studied at wytham farm oxford university in southern england in the first field season field drain water contained high concentrations of pesticide soil studies demonstrated that the main mechanism for pesticide translocation was by preferential flow processes both over the soil surface and through the soil profile via a macropore system that effectively by passed the soil matrix this macropore system included worm holes shrinkage cracks and cracks resulting from ploughing rainfall events in early winter rapidly created a layer of saturation in the a horizon perched above a b horizon of very low hydraulic conductivity drain flow was initiated when the saturated layer in the a horizon extended into the upper 0 06m of the soil profile thereafter water moved down slope via horizontal macropores possibly through a band of incorporated straw residues these horizontal pathways for water movement connected with the fracture system of the mole drains thus feeding the drains overland flow occurred infrequently during the season

evidence for a panafrican volcanic arc and wrench fault tectonics in the jbel saghro anti atlas morocco the saghro hills constitute the northern branch of the panafrican mobile belt in the eastern part of the moroccan anti atlas the precambrian terranes are predominantly composed of volcaniclastic and volcanic series witnessing a mainly explosive volcanism intruded by diorites and granites their age attribution is problematic and has been reconsidered in the present study based on structural evidence and rb sr data of quartzdiorites penetratively deformed volcano sedimentaries intruded by these plutons aged between 754 and 722 ma are now considered as lower precambrian ii the upper pii series have been reattributed and only formations overlying a basal conglomerate and angular disconformity are considered piii

mixing in mantle magma reservoirs prior to and during the 2011 2012 eruption at el hierro canary islands understanding magmatic systems feeding volcanoes is critical for accurate interpretation of monitoring data and ultimately eruption forecasting following 3 months of precursory unrest the first historical eruption at el hierro canary islands took place 2 km offshore from october 2011 to march 2012 our detailed petrological analysis of lava samples reveals that at least two distinct magmas initially supplied from reservoirs in the mantle underwent hybridization at 15 25 km depth i e also largely within the upper mantle beneath el hierro diffusion chronometry applied to zoned olivine crystals indicates that magma mixing began during the period of preeruptive seismicity and continued for weeks after the eruption onset our data also capture a magma stagnation level at 10 15 km depth in the lower crust consistent with lateral propagation of an intrusion over substantial distances before rapid magma transit to the seafloor the remarkable spatial and temporal correlation of petrological and geophysical data at el hierro suggests that the observed seismicity records magma mixing and forceful intrusion as well as subsequent reservoir dynamics these results demonstrate that eruptions at el hierro are controlled principally by deep seated processes with little influence from shallow crustal levels and have important implications for monitoring of renewed unrest at long dormant volcanoes

understanding crystal populations and their significance through the magma plumbing system crystals are rarely composed of a single crystal population that have grown solely from the batch of magma in which they are resident on emplacement either by eruption or shallow intrusion close investigation of the majority of crystal populations reveal that they comprise up to four main components phenocrysts crystals co genetic with their magmatic host xenocrysts crystals wholly or in part foreign to the magmatic host and magma system antecrysts crystals which are recycled one or several times before inclusion in the host magma but have an origin within the magmatic system and microlites which represent small co genetic crystals which nucleate and grow rapidly on decompression and eruption textural analysis techniques are employed to quantify key aspects of the crystal population including crystal shape crystal size distributions spatial distribution patterns and textural modification using dihedral angles santorini provides a case study of an active volcanic system where a combined textural analysis study has been developed highlighting how the crystal population is being continuously modified by a series of replenishment and mixing events developing textural and microgeochemical techniques provides the next stage in the interrogation of crystal populations linking textures to isotopic heterogeneities and providing fingerprints of where crystals are sourced and re cycled

high resolution la icp ms trace element mapping of igneous minerals in search of magma histories we report experiments on optimisation of la icp ms mapping as a tool for visualising and quantifying internal structure of trace element concentration in igneous minerals the experimental design was refined with maps on clinopyroxene and amphibole macrocrysts mainly antecrysts from a porphyritic lamprophyre in ne spain as well as on a high precision metal wire grid in terms of spatial resolution we demonstrate with scanning electron microscope and white light interferometry that a full ablation removes between 0 4 and 0 7 mu m of material depending on ablation parameters maps were produced with square laser beam spots of 12 and 24 mu m it was found that complexities can be resolved in the sample even though they are smaller than the beam diameter e g 7 10 mu m discontinuities using 12 mu m laser beam resolution in x and y was found to be identical probably reflecting the fast washout of the two volume ablation cell and the short total dwell time of the analyte menu selected due to the excellent stage reproducibility and the limited ablation depth it is feasible to re ablate the identical map area many times employing different instrument parameters or analyte menus on the magmatic crystals la icp ms maps define very sharp compositional zoning in trace elements highlighting complex crystallisation histories where normal magmatic fractionation is not the only process events of mafic recharge are easily recognised as zones enriched in compatible metals such as cr ni or sc further trace element maps reveal complexities in mineral zoning previously undetectable with petrography or major element data these include resorbed primitive cores and oscillatory zoning within apparently homogeneous mineral zones therefore la icp ms mapping opens a new window of opportunity for analysis of magmatic histories the wide combination of instrumental parameters such as laser beam size scan speed and repetition rate make it possible to carry out experiments at different levels of detail we recommend a two step approach to mapping the initial step involves rapid maps to gain an overview of potential complexities in the sample this enhances representativeness of the analysed materials as a large number of crystals and trace elements can be tested in little time subsequently detailed maps can be carried out on areas of interest an additional functionality is to create 1d profiles from 2d maps the potential of the technique to unveil compositional complexities efficiently and at greater detail than traditional microanalysis will help to improve our understanding of processes in the magmatic environment and beyond c 2015 elsevier b v all rights reserved