classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

influence of successive phases of volcanic construction and erosion on mayotte island s hydrogeological functioning as determined from a helicopter borne resistivity survey correlated with borehole geological and permeability data summary the purpose of this study is to show how a multidisciplinary approach that combines geophysics geology and hydrogeology has made it possible to a significantly improve our understanding of the hydrogeological regime of the volcanic island of mayotte and b provide a new set of geophysical measurement calibration data in 2010 a helicopter borne geophysical survey skytem was flown over the entire island 374 km2 with a measurement density hitherto unheard of in a volcanic environment in addition a database was compiled containing the geological logs of 55 boreholes 52 of these boreholes have hydrogeological information like aquifer position and piezometric level 21 of the boreholes have transmissivity values correlations were made between the inverted resistivities as obtained from the helicopter borne tdem profiles and the nature age and hydrodynamic properties of the formations as obtained from the borehole data five hydrogeological units were mapped these are characterized by an alternation between phases of dominant volcanic construction with the emplacement of basaltic lavas phonolite massifs and pyroclastic deposits and phases of dominant erosion with the deposition of volcaniclastic material colluvium breccias basaltic lavas and phonolite blocks and all materials resulting from slope slides along the slopes and in the topographic depressions it has also been possible to assign resistivity and permeability ranges to four of these units ranges that are also dependent on the age of the deposits the younger the formation is the greater its resistivity and the higher its permeability the hydrogeological regime is marked by the phases of volcanic construction and erosion that succeeded one another during the geological history of mayotte over the last 10 ma a conceptual model adapted to the specific geological context of this island and differing from the canarian and hawaiian models is also put forward this model is marked by the island s fragmented character resulting from its geological history several volcanic edifices several phases of construction and erosion and is applicable to an old volcanic island in an advanced stage of erosion and weathering with a volcanic history similar to that of mayotte i e with climate variations and erosion periods long enough to register volcaniclastic deposits

melting curve of mg fe sio3 perovskite to 96 gpa evidence for a structural transition in lower mantle melts the melting temperature of mg fe sio3 perovskite the dominant mineral phase of the earth s lower mantle has been measured to a pressure of 96 10 gpa below 60 gpa we find good agreement with the previous measurement of heinz and jeanloz 1987a and above 60 gpa the melting curve of silicate perovskite has a small positive slope of 19 5 5 5 k gpa the melting point of mg0 9fe0 1 sio3 perovskite is 3800 300 k at 96 gpa by extrapolation to 136 gpa it is 4500 500 k at the core mantle boundary these values provide an upper limit to the geotherm through the solid mantle and they are compatible with recent estimates of the temperature in the core being high 4500 k at the core mantle boundary our melting curve implies that the volume change on melting increases at 60 gpa from vm 0 0 0 2 cm mole to vm 0 16 0 03 cm mole we derive an equation of state for the melt from our data and find that a highly coordinated structure is required to explain the molar volume of liquid mg fe sio3 at pressures above 20 gpa

sedimentary evolution of the torrecilla reef complex in response to tectonically forced regression early kimmeridgian northern spain the early kimmeridgian torrecilla reef complex in the northern iberian basin of spain consists of a fringing reef composed of eight accretionary units the first four were deposited along a steep margin they display down lapping and off lapping geometries and are characterised by poor reef framework development large volumes of reworked corals and transported sediment and limited growth of micro encrusters in contrast deposition of the fifth and younger accretionary units occurred on a shallow platform without a pronounced slope where coral reefs grew in a shallow protected environment the main features of these reefs are an absence of reef slope facies a high proportion of preserved framework elements relatively low volumes of intrareef sediment high proportions of terrigenous material and abundant micro encrusters and microbialites these reefs were protected from storm waves by long shore sand bars which also protected a very shallow lagoon during the last stage of sedimentation the early kimmeridgian was a period of rising global sea level a trend apparent across other portions of the iberian basin however geometry and sedimentary evolution of the torrecilla reef complex is consistent with those of off lapping reefs that develop during sea level fall thus we conclude that down stepping geometries and evolution to progressively shallower environments within the torrecilla reef complex occurred as a result of a tectonically forced regression d 2005 elsevier b v all rights reserved

elasticity of mgsio3 in the ilmenite phase abstract the single crystal elastic moduli of the ilmenite phase of mgsio 3 have been determined from brillouin spectroscopy they are c 11 472 c 12 168 c 33 382 c 13 70 c 44 106 c 14 27 c 66 152 and c 25 24 in gpa these elastic properties are consistent with a structural mechanical model where the silicon octahedra are very stiff under compression and shear this latter property yields an unexpectedly high shear modulus for the magnesium silicate ilmenite as compared with analogue compounds the further transformation to perovskite will probably be associated with a significant increase in elastic properties since the strong silicon polyhedra form a structural network in this phase the transformation of spinel and stishovite to ilmenite is associated with a slight density increase and a slight decrease in acoustic velocities this transformation will probably not produce a seismic discontinuity even if it does occur in the earth s mantle

a conceptual hydrodynamic model of a geological discontinuity in hard rock aquifers example of a quartz reef in granitic terrain in south india summary the structure and hydrodynamic properties of geological discontinuities and of a deeply weathered granite aquifer near these structures are described on the basis of geological geophysical and hydrodynamic investigations in two sites of south india located along a 20 40 m wide quartz reef intruding a weathered archean biotite granite one of the two sites also comprises a metre wide dolerite dyke weathering processes appear to be at the origin of fissures development and of a related enhanced local hydraulic conductivity both in the quartz reef and in the surrounding granite the weathering profile in the granite saprolite and fissured layer is characterized by an abrupt deepening of the weathered layers in the granite near the contact and in the quartz reef itself therefore the weathering profile shows a u shape geometry with among others the verticalization of the granite s fissured layer the hydraulic conductivity of this verticalized layer is on average 5 10 6 m s and storativity about 10 3 the hydraulic conductivity of the fissured quartz is 4 6 10 6 m s and its storativity about 3 5 10 4 both media are also characterized by a matrix hydraulic conductivity 10 7 10 9 m s and by a significant heterogeneity in hydrodynamic properties that generates preferential flow paths along the sub vertical fissures parallel to the reef axis a special attention has been paid for characterizing this heterogeneity the weathering of the dolerite dyke however results in a local low hydraulic conductivity which consequently does not enhance either the thickness of weathered granite layers or its hydraulic conductivity the obtained results complete the conceptual hydrogeological model developed for weathered granite aquifers in characterizing the relationships between weathering processes and hydrodynamic properties near geological discontinuities

phase relation and physical properties of an al depleted komatiite to 23 gpa abstract knowledge of the mineralogical constituents of the earth s mantle depends heavily on high p experiments of pyrolite composition in order to understand the planetary interior better phase relations and mineral physics properties of compositions other than pyrolite may also be important high p and high t experiments were conducted on an al depleted komatiite which can be regarded as a kind of piclogite composition fourteen experiments were carried out along a model geotherm between 5 and 23 gpa and 1100 and 1600 c with a multi anvil apparatus analyses of quenched run products showed that in the studied komatiite the fractions of olivine and its high p polymorphs wadsleyite and ringwoodite are 40 50 vol pyroxene garnet phase transition occurs at 13 17 gpa while the respective values for pyrolite are 60 vol and 12 15 gpa the density and seismic velocity profiles of komatiite mantle were calculated using thermoelastic parameters of related minerals and they showed quite good agreements with those of seismic observations around the transition zone as well as those for pyrolite

thermal expansion measurements at very high pressure systematics and a case for a chemically homogeneous mantle new data on thermal expansivity of iron to over 400 kbar in laser and electrically heated diamond anvil cells and on mgo and forsterite from spectroscopic data to over 200 kbar and previously measured adiabats boehler 1982 imply that at high pressure may be described by a constant value of 1n 1nv t 5 5 0 5 this behavior is supported by previous measurements at lower pressures on a large variety of materials densities of magnesio wustite and silicate perovskite in a pyrolitic ratio calculated at lower mantle conditions using a finite strain equation and at high pressures using the above systematics match those in prem through the entire lower mantle making a strong case for a uniform mantle

extensive perched aquifer and structural implications revealed by 3d resistivity mapping in a galapagos volcano abstract due to the complexity of geological formations and limited subsurface data in volcanic islands hydrogeological conceptual models can differ from one island to another and for the same island the galapagos islands like most inhabited volcanic islands face important water resource problems which might have a major impact on their unique and pristine ecosystems endanger world heritage list june 2007 the scarcity of geological and hydrological data combined with the difficulty of access for field measurements lead to a poor understanding of the island hydrogeology and unconvincing interpretation of traditional geophysical data here we present three dimensional 3 d resistivity maps for the supposedly waterless santa cruz island obtained by using the skytem device a helicopter borne transient electromagnetic method the latter is non invasive and measurements over inaccessible terrain were of vital importance we show that even in high relief terrain with extreme subsurface resistivity contrasts 1 6 000 ohm m the method is sensitive to low resistivity layers of hydrogeological interest 50 200 ohm m to a depth of approximately 300 m the unique spatial resolution and 3 d view of the subsurface resistivity structures allow identification of two zones of hydrogeological importance a previously unknown extensive perched aquifer 50 km 2 on the southern mountain side and the geometry of the salt water wedge in the basal aquifer located with an accuracy of a few meters this finding supports the existence of hidden perched aquifers on basaltic islands until now only inferred from hydrogeological studies it is seen to be affected by faulting beyond the vital implications for water resource and ecosystem management in the unique yet severely threatened galapagos islands some conceptual flow models of volcanic islands have to be reconsidered the presence of such structures in a volcanic edifice recognized as low strength layer may help to explain the origin of potentially catastrophic landslides

depth of investigation in electromagnetic sounding methods the time or frequency at which the electromagnetic em response of a buried inhomogeneity can first be measured is determined by its depth of burial and the average conductivity of the overlying section it is relatively independent of the type of source or receiver and their separation the ability to make measurements at this time or frequency however depends on the sensitivity and accuracy of the instrumentation the signal strength and the ambient noise level these factors affect different em sounding systems in surprisingly different ways for the magnetotelluric mt method it is possible to detect a buried half space under about 1 5 skin depths of overburden the maximum depth of investigation is virtually unbounded because of high signal strengths at low frequencies transient electromagnetic tem soundings on the other hand have a limited depth of penetration but are less affected by static shift errors for tem a buried inhomogeneity can be detected under about one diffusion depth of overburden for conventional near zone sounding in which induced voltage is measured impulse response the depth of investigation is proportional to the 1 5 power of the source moment and ground resistivity by contrast if the receiver is a magnetometer step response system the depth of investigation is proportional to the 1 3 power of source moment and is no longer a function of resistivity magnetic field measurements may therefore be superior for exploration in conductive areas such as sedimentary basins far zone or long offset tem soundings are traditionally used for deep exploration the depth of investigation for a voltage receiver is proportional to the 1 4 power of source moment and resistivity and is inversely proportional to the source receiver separation magnetic field measurements are difficult to make at long offsets because instrumental accuracy limits the measurement of the very slow decay of the magnetic field frequency domain controlled source systems are ideally suited for sounding at the very shallow depths needed for engineering archaeological and groundwater applications because of the relative ease of extending the measurements to arbitrarily high frequencies and also because geometric soundings can be made at low induction numbers

major natural hazards in a tropical volcanic island a review for mayotte island comoros archipelago indian ocean abstract mayotte is a french overseas territory of the comoros archipelago since the 1980 mayotte has developed quickly its population has multiplied by four in less than 30 years infrastructure expanded rapidly in lowlands and slums developed in steep areas through deforestation or close to riverbeds this development urgently required steps to ensure the safety of urban areas from 2002 to 2006 a major programme of natural hazards evaluation and zonation was conducted by the french geological survey in the 17 districts of mayotte the programme resulted in the publication of the first single hazard zonation maps for mayotte at 1 25 000 scale in rural areas and at 1 10 000 scale in urban areas hazard maps regarding landslides and rock falls stream floods seismic lithological and topographical amplification potential liquefaction potential and cyclonic marine submersion were produced for mayors and land planners these atlases also included prevention guidelines to minimize risks associated with land use or urbanization within hazard prone areas this article presents the main achievements of the programme whose main problems were the absence of archives of previous studies and the original volcanic geology of the island of mayotte the atlases highlight areas with numerous landslides zones susceptible to flash floods sectors likely to be submerged by storm surges and areas subject to seismic site effects due to thick volcanic weathered formations this programme emphasizes the fundamental role in such tropical volcanic islands of a good knowledge of the weathered formations for the assessment of most natural hazards this initial hazard mapping represented the first step to achieve specific regulatory risk prevention plans for an efficient land use risk mitigation and reduction policy in mayotte

extremal bounds on the seismic velocities in the earth s mantle summary based on global travel time constraints of the function p lee johnson the confidence region for the lower mantle p and s velocity profiles have been determined an exact method bessonova et al is used to compute the extremal bounds on velocity bounds on the lower mantle p velocity have an average resolution of 70 km in the depth range of 800 2900 km the average bound width is 0 14 km s 1 at the 97 per cent confidence level bounds on the lower mantle s velocity have an average resolution of 85 km in the depth range 850 2900 km and an average width of 0 13 km s 1 these results indicate that significant differences exist among the published velocity models and that the bounds can be used to discriminate among them the confidence regions are computed with an assumed upper mantle velocity model and are therefore subject to small baseline adjustments in velocity the introduction of approximate bounds on the upper mantle p increases the lower mantle bound width by 30 per cent for the p velocity in this case one obtains constraints on the absolute velocity function

chemical stratification of the mantle formed by melting in the early stage of the terrestrial evolution abstract the accretional growth of the earth necessarily involved a molten zone in the outer layer magma ocean of the growing earth resulting in downwards extraction of the molten iron alloy i e core formation the primary stratification resulted from melting in the accretional stage of the earth and consisted of an fe core a perovskite rich lower mantle and a partially molten ultrabasic upper mantle in which the melt was concentrated in two regions near the surface of the cooling gravitational differentiation and crystallization in the magma ocean should give rise further to a finer stratification the upper mantle composed of two layers the upper olivine rich layer and the lower majorite garnet rich layer and the lower mantle with a perovskite rich composition both the 400 and 670 km discontinuities of the present mantle may be the chemical boundary the geophysical constraints of the mantle i e the seismic wave velocity and density profiles favor such a stratified mantle

groundwater salinization in the azores archipelago portugal groundwater salinization in coastal regions causes severe constraints to water supply and economic losses to society worldwide in the azores archipelago groundwater abstraction in wells drilled in coastal aquifers is very important for water supply and quality problems have been reported therefore a groundwater chemistry dataset from wells was compiled to study groundwater salinization in these aquifers waters are mainly of the na cl type presenting a slightly acidic to slightly alkaline character with a ph between 5 63 and 8 50 median 7 40 electrical conductivity measurements range from 127 to 9 670 s cm median 862 suggesting highly variable mineralization with higher values observed on santa maria sao miguel pico graciosa and sao jorge islands the major ion composition reflects the contribution of seawater to the groundwater compositional evolution which is essentially explained by seawater intrusion into wells in many samples exchange reactions of na k for ca2 mg2 are associated with salinization the seawater fraction in groundwater composition reaches a maximum of 22 5 these results are extremely challenging to water managers in the azores because failure to comply with national water quality regulations and with european union groundwater directive requirements often occurs

heterogeneity of hydrodynamic properties and groundwater circulation of a coastal andesitic volcanic aquifer controlled by tectonic induced faults and rock fracturing martinique island lesser antilles fwi summary we conducted a multidisciplinary study to analyze the structure and the hydrogeological functioning of an andesitic coastal aquifer and to highlight the importance of faults and associated rock fracturing on groundwater flow a helicopter borne geophysical survey with an unprecedented resolution skytem was flown over this aquifer in 2013 tdem resistivity total magnetic intensity geological and hydrogeological data from 30 boreholes and two pumping tests were correlated including one which lasted an exceptional 15 months we demonstrate that heterogeneous hydrodynamic properties and channelized flows result from tectonically controlled aquifer compartmentalization along the structural directions of successive tectonic phases significant fracturing of the central compartment results in enhanced hydrodynamic properties of the aquifer and an inverse relationship between electrical resistivity and transmissivity basalts within the fractured compartment have lower resistivity and higher permeability than basalts outside the compartment pumping tests demonstrate that the key factor is the hydraulic conductivity contrast between compartments rather than the hydrodynamic properties of the fault structure in addition compartmentalization and associated transmissivity contrasts protect the aquifer from seawater intrusion finally unlike basaltic volcanic islands the age of the volcanic formations is not the key factor that determines hydrodynamic properties of andesitic islands basalts that are several million years old 15 ma here have favorable hydrodynamic properties that are generated or maintained by earthquakes faulting that result from active subduction beneath these islands which is superimposed on their primary permeability

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

origin of the permian triassic iberian basin central eastern spain abstract the iberian basin was an intracratonic rift basin in central eastern spain developed since early permian times the basin boundary faults were normal listric faults controlling an asymmetric extension propagating northeast with time hercynian or older lineaments controlled the orientation of the iberian basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high the basin was related with the coeval ebro catalan and cuenca mancha basins and their connections are discussed subsidence curves show that the early permian early jurassic period of extension can be subdivided into three rifting episodes and a flexural one extension factor increases from 1 17 in the northwest to 1 29 near the mediterranean coast the increasing extension rate was accommodated by transfer faults trending nne ssw more important in the levante area the rift evolution is intermittent and seems to reflect distinct stress fields the collapse of the late hercynian orogen and related increased heat flux extension and rifting is the most probable origin of the iberian basin and related basins the origin of the catalan and the valencia prebetic basins is related to the southwards migration of the hesse burgundy rift along the eastern margin of the iberian microplate

criteria for recognition of localization and timing of multiple events of hydrothermal alteration in sandstones illustrated by petrographic fluid inclusion and isotopic analysis of the tera group northern spain stratigraphic relations detailed petrography microthermometry of fluid inclusions and fine scale isotopic analysis of diagenetic phases indicate a complex thermal history in tithonian fluvial sandstones and lacustrine limestones of the tera group north spain two different thermal events have been recognized and characterized which are likely associated with hydrothermal events that affected the cameros basin during the mid cretaceous and the eocene multiple stages of quartz cementation were identified using scanning electron microscope cathodoluminescence on sandstones and fracture fills primary fluid inclusions reveal homogenization temperatures th from 195 to 350 c in the quartz cements of extensional fracture fillings the high variability of th data in each particular fluid inclusion assemblage is related to natural reequilibration of the fluid inclusions probably due to cretaceous hydrothermal metamorphism some secondary fluid inclusion assemblages show very consistent data th 281 305 c and are considered not to have reequilibrated they are likely related to an eocene hydrothermal event or to a retrograde stage of the cretaceous hydrothermalism this approach shows how multiple thermal events can be discriminated a very steep thermal gradient of 97 214 c km can be deduced from 18o values of ferroan calcites 18o 14 2 11 8 v pdb that postdate quartz cements in fracture fillings furthermore illite crystallinity data anchizone epizone boundary are out of equilibrium with high fluid inclusion th these observations are consistent with heat flux related to short lived events of hydrothermal alteration focused by permeability contrasts rather than to regional heat flux associated with dynamo thermal metamorphism these results illustrate how thermal data from fracture systems can yield thermal histories markedly different from host rock values a finding indicative of hydrothermal fluid flow

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

characterization of the source rocks of a paleo petroleum system cameros basin based on organic matter petrology and geochemical analyses abstract the cameros basin is a paleo petroleum system formed in the north eastern iberian peninsula the basin formed during the mesozoic iberian rift and was later inverted during the alpine orogeny hydrothermal events took place during the post extensional and inversion stages producing an important impact on the thermal history of the basin in order to determine the source rock of the petroleum system of the basin organic matter characteristics the petroleum generation potential and the maturity of the basin infill are determined by means of petrology and geochemical analyses several organic rich units of the stratigraphic record of the basin are potential source rocks for hydrocarbons generation although their characteristics differ depending on their location organic matter content in the northern sector is scarce and limited to vitrinite inertinite and solid bitumen particles the residual total organic carbon toc the different evolution of the source rocks in the basin is the result of the combination of differential subsidence rates which determine different thermal histories and of the circulation of hydrothermal fluids in the northern central sector during the evolution of the basin

mesozoic extensional tectonics stratigraphy and crustal evolution during the alpine cycle of the eastern iberian basin abstract sequence stratigraphy subsidence analysis and the integration of the basin fill data allow to the identification of four successive evolutionary stages in the basins of the eastern iberian margin during mesozoic extension 1 triassic rift late permian hettangian 2 early and middle jurassic postrift sinemurian oxfordian 3 late jurassic and early cretaceous rift kimmeridgian middle albian and 4 late cretaceous postrift late albian maastrichtian the present day crustal structure of the eastern iberian range and evidence of its evolution are deduced from the analysis of a new gravity map and other geophysical data a regional gravity low along the iberian range is interpreted in terms of crustal thickening beneath the orogen as a result of the collision between the ebro block and the iberian plate during the paleogene the boundary between these blocks coincides with a magnetic lineament that is interpreted as an inherited signature of the thinning that occurred during mesozoic extension a geodynamic scenario for the crustal evolution of the eastern part of the iberian peninsula based on the evaluation of mesozoic extensional tectonics and an analysis of the available geophysical data includes three main successive evolutionary stages 1 1 mesozoic crustal thinning 2 2 paleogene crustal thickening 3 3 neogene crustal thinning based on new geological and geophysical arguments this study offers an alternative and a more complete geodynamic history of the eastern iberian basins related to the evolution of the iberian plate and the central north atlantic

answer to the comment of casas et al about gonzalez acebron et al s 2011 paper the comment of casas et al concerns the paper published by gonzalez acebron et a1 201 1 and refers mostly to their model for the structural and thermal events in the sedimentary record late jurassic eady cretaceous from the cameros basin their model differs significantly from the interpretations previously published by mas et a1 1993 guimera et a1 1995 20m and mas and salas 2002 their main concern appears to be the difference of opinion about the previously published structural evolution of the basin not the results of our new study rather than debate the earlier more appropriate papers they have chosen this our marginally related paper to air their dif ferent view of the structural interpretations our paper did not concern evidence for interpretations of the structural evolution of this basin which had already been published and peer reviewed we clearly stated that we had excluded their model for consideration relative to our new data why we had done so and referred to the appropriate peer reviewed literature thus we must question whether this is

analytical solutions for analysing pumping tests in a sub vertical and anisotropic fault zone draining shallow aquifers summary we present new analytical solutions for examining the influence during a pumping test in a well of an infinite linear and anisotropic strip aquifer that drains shallow aquifers of different diffusivity and thickness the whole system is confined and the aquifer geometry can be represented by a t an aquifer geometry resembling a sub vertical fault or a sub vertical vein cross cutting shallower aquifers the proposed solutions are based upon an unconventional application of well image theory without limitation of the diffusivity contrast between the three domains solutions for drawdown were developed for the three domains i e the strip aquifer and the two shallow compartments and flow signatures are discussed in detail and compared to numerical modelling the proposed solutions are not shown to be exact solutions to the appropriate partial differential equation but very good and useful approximations the solutions were applied to a 63 day pumping test in a steep fault zone in crystalline aquifer rock of brittany france after that the flow contributions of the fault zone and of the shallow aquifers deduced from groundwater dating were compared to analytical solutions the solutions and theoretical type curve examples can help in understanding flow processes from tests conducted in settings that are similar to such a conceptual model

structure and hydrogeological functioning of an insular tropical humid andesitic volcanic watershed a multi disciplinary experimental approach summary the aim of the study is to establish an hydrogeological scheme of the structure and the functioning of andesitic volcanic systems in the insular and humid tropical context a watershed has been instrumented at fefe in guadeloupe french west indies in the lesser antilles to measure rainfall runoff and piezometric fluctuations between 2003 and 2006 given the heterogeneity of the volcanic deposits a multi disciplinary approach has been used a geological and an hydrogeological survey an hydrodynamic approach hydraulic tests and signal processing of hydrological time series and finally an hydrogeochemical approach major elements and some trace elements two main superposed aquifer respectively in aerial deposits and in recent nuees ardentes glowing ash and lava flows as well as the underlying aquiclude the highly weathered older substratum were identified at a local scale some hydrogeological heterogeneities internal to the aquifers were highlighted and related to a polyphased building up of the geological formations hydraulic relationships between the multi layered aquifers such as the confinement of the deep aquifer upstream of the basin were identified groundwater stream exchanges were characterised detailing various contributions of the shallow and the deep aquifers to stream and spring waters significant river losses were also observed at a global scale within such relatively permeable volcanic formations the aquifer recharge is about 85 of the annual effective rainfall for an average rainfall year the hydrogeological scheme appears to be coherent with a geological structure of cut and fill paleovalleys frequently observed in andesitic areas consequently groundwater drainage axis are mainly localised in recent nuees ardentes deposits whereas the inversion of relief characteristic of volcanic areas explains the non superposition of surface water and groundwater divides and both surface water losses and springs finally this work shows the highly heterogeneous hydrogeological processes occurring in volcanic formations of andesitic type it also shows the relationships between the geological structure and the hydrogeological functioning of such basins and proposes an affordable methodological approach to investigate such a hydrogeological context in depth

tectono stratigraphic evolution of an inverted extensional basin the cameros basin north of spain the cameros basin is a part of the mesozoic iberian rift it is an extensional basin formed during the late jurassic and early cretaceous in the mesozoic iberian rift context and it was inverted in the cenozoic as a result of the alpine contraction this work aims to reconstruct the tectono stratigraphic evolution of the basin during the mesozoic using new and revised field geophysical and subsurface data the construction of a basin wide balanced section with partial restorations herein offers new insights into the geometry of the syn rift deposits field data seismic lines and oil well data were used to identify the main structures of the basin and the basin forming mechanisms mapping and cross sectional data indicate the marked thickness variation of the depositional sequences across the basin suggesting that the extension of the depositional area varied during the syn rift stage and that the depocentres migrated towards the north from field observation and seismic line interpretation an onlap of the depositional sequences to the north over the marine jurassic substratum can be deduced in the last few decades the structure and geometry of the basin have been strongly debated the structure and geometry of the basin infill reconstructed herein strongly support the interpretation of the cameros basin as an extensional ramp synclinal basin formed on a blind south dipping extensional ramp the gradual hanging wall displacement to the south shifted the depocentres to the north over time thus increasing the basin in size northwards with onlap geometry on the pre rift substratum the basin was inverted by means of a main thrust located in a detachment located in the upper triassic beds keuper which branched in depth with the mesozoic extensional fault flat the reconstruction of the tectono stratigraphic evolution of the cameros basin proposed herein represents a synthesis and an integration of previous studies of the structure and geometry of the basin this study can be used as the basis for future basin scale research and for modelling the ancient petroleum system of the basin

three common source rock evaluation errors made by geologists during prospect or play appraisals geologists are frequently called on to evaluate the source rocks associated with their exploration prospects or plays the three most common questions asked and answered about the source rock during project reviews are what s the total organic carbon toc what kerogen type does rock eval indicate and what maturity level does the vitrinite reflectance data point to the answers to these seemingly innocuous questions may in fact be providing a false sense of security about the source rock in question understanding how this line of questioning can lead you astray and make you the victim of the toc myth if i have high toc i have a good source rock the rock eval fallacy the rock eval data tell me what kind of kerogen is in my source rock and the vitrinite reflectance deficiency vitrinite reflectance will tell me if my source rock is generating is important some of the solutions to these problems include fully integrating toc and rock eval data supplementing rock eval data with pyrolysis gas chromatography and using burial history diagrams to help interpret vitrinite reflectance harry dembicki jr is a senior geological advisor for geochemistry in the geological technology group at anadarko petroleum corporation where he provides technical support to both exploration and development teams he holds a b s degree 1973 in geology from the state university college of new york at new paltz and a ph d 1977 in geology with emphasis in organic geochemistry from indiana university he previously worked as an organic geochemist for conoco and marathon

melting of garnet peridotite to 13 gpa and the early history of the upper mantle by analogy with the evolution of the moon it has been suggested that the earth may have had a magma ocean or liquid outer layer before 3 800 myr ago 1 its presence would have had profound implications for the primary stratification of the mantle into upper mantle transition zone and lower mantle2 3 an essential constraint on this hypothesis is a knowledge of the high pressure melting characteristics of mantle material generally assumed to be peridotite in the upper mantle we recently described4 the first melting experiments on mantle peridotite to 14 gpa using spinel iherzolite klb 1 from kilbourne hole new mexico we showed that partial melts close to the solidus at 5 7 gpa are komatiitic in composition and that the solidus and liquidus converge at high pressures here we report further melting experiments on garnet iherzolite phn1611 from thaba putsoa lesotho we confirm the convergence of the solidus and liquidus and we show a negative dt dp slope for the liquidus above 7 gpa these observations are briefly discussed in terms of their importance to the petrological evolution of the upper mantle and the presence of a magma ocean in the early archaean

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

an experimental investigation of the pyroxene garnet transformation in a pyrolite composition and its bearing on the constitution of the mantle abstract the pyroxene garnet transformation in a model pyrolite composition has been investigated over the pressure interval 4 0 to 17 5 gpa at temperatures of 1200 1400 c the transformation is largely completed in the pressure interval 14 16 gpa and a single phase aluminum deficient garnet majorite becomes stable above 16 gpa the mineral assemblages and the density and seismic velocity distributions for pyrolite are calculated as a function of depth on the basis of this and other recent experimental data density and seismic velocity profiles calculated for pyrolite are consistent with models based on seismic observations to a depth of 550 km if the existence of a high density velocity gradient between 550 km and 650 km is confirmed the presence of further phase transformations in majorite and or some degree of chemical heterogeneity in this depth interval would be indicated

fundamental thermodynamic relations and silicate melting with implications for the constitution of d we describe fundamental thermodynamic relations helmholtz free energy as a function of volume and temperature for solids and liquids simple physically based expressions which contain all thermodynamic information about a system the solid fundamental relation consists of debye and birch murnaghan finite strain theory combined in the mie gruneisen framework the liquid fundamental relation is derived by taking the high temperature limit of the solid expression we derive the liquid equation of state which contains only four parameters from the liquid fundamental relation and show that it successfully describes measurements of liquid alkali metals water and liquid diopside over a wide range of pressure and temperature we find optimal fundamental relation parameters for diopside enstatite ilmenite and perovskite and find the solid relation to be in excellent agreement with data including heat capacities thermal expansion and mgsio3 phase equilibria we then combine the liquid and solid fundamental relations to calculate the melting curves of diopside enstatite and perovskite which are found to be in excellent agreement with experiment all predicted melting curves have dt dp slopes which decrease steadily with pressure eventually becoming negative because of liquid crystal density inversion our predicted melting temperature of perovskite in the d region 3750 k at the base of the mantle is thousands of degrees lower than previous estimates yet it is consistent with experimental data the predicted melting curve although consistent with the lack of widespread melting in the lower mantle is much lower than recently proposed geotherms in the d layer at the base of the mantle by combining our results with seismic observations of the deep mantle we propose that the d layer consists of magnesiowustite and silica in the form of stishovite or its recently discovered high pressure modification

changes in optical properties of liptinite macerals from early mature to post mature stage in posidonia shale lower toarcian nw germany abstract detailed organo petrological analysis was carried out on core samples of posidonia shale lower toarcian from two wells which are located in northwestern germany lower saxony basin organic matter in one well is early mature vrr 0 5 whereas organic matter in the other is post mature vrr 3 5 results of organo petrological analyses demonstrate that telalginite tasmanales alginite in early mature oil shales appears brown to dark brown in reflected white light whereas in fluorescence mode it shows a yellow color of high intensity in contrast in post mature oil shales relics of former telalginite named postmature telalginite for the purposes of the maceral analysis occur in three forms of replacement of former telalginite bodies whose shape and size are preserved one form consists of a chain of carbonate crystals or of a completely recrystallized calcareous mass both are associated with homogeneous and heterogeneous migrabitumen the second form is completely composed of epigenetic pyrite the third form of postmature telalginite is rare and consists of impsonite in mature posidonia shale lamalginite is relative frequent and has been encountered in three forms discrete 10 m and layered in post mature posidonia shale all these forms are no longer recognizable part of the micrinite dispersed in the mineral groundmass may have been derived from lamalginite in oil shales of early mature stage bituminite i is characterized by a very low reflectance and a brownish fluorescence color it often includes yellow fluorescent liptodetrinite and has indistinct lense shape on the contrary in post mature oil shales on the basis of morphology it appears as light gray lenses which consist of massive micrinite bituminite ii in early mature oil shales occurs as thick elongated homogeneous lenses and streaks associated with tiny carbonate crystals and with yellow brownish fluorescence often with greenish fluorescent oil expulsions in post mature oil shales postmature bituminite ii consists of a network of micrinite between tiny carbonate crystals apart from these common bituminites minor contents of other bituminites have been recorded sporinite in early mature oil shales has a very low reflectance and an orange brown fluorescence of moderate intensity in post mature oil shales sporinite shows reddish orange internal reflections and is filled with pyrite crystals or with weak fluorescing minerals which emphasize the sporinite form this study demonstrates that the use of the terms postmature telalginite postmature bituminite and postmature sporinite in the macerals analysis of post mature oil shales is highly profitable particularly in understanding the transformation processes which are the result of the formation of secondary products secondary macerals and epigenetic minerals in the primary liptinite macerals

effect of volcanic dykes on coastal groundwater flow and saltwater intrusion a field scale multiphysics approach and parameter evaluation volcanic dykes are common discrete heterogeneities in aquifers however there is a lack of field examples of and methodologies for comprehensive in situ characterization of their properties with respect to groundwater flow and solute transport we have applied an integrated multi physics approach to quantify the effect of dolerite dykes on saltwater intrusion in a coastal sandstone aquifer the approach involved ground geophysical imaging passive magnetics and electrical resistivity tomography well hydraulic testing and tidal propagation analysis which provided constraints on the geometry of the dyke network the subsurface saltwater distribution and the sandstone hydrodynamic properties and connectivity a three dimensional variable density groundwater model coupled with a resistivity model was further calibrated using groundwater and geophysical observations a good agreement of model simulations with tide induced head fluctuations geophysically derived pore water salinities and measured apparent resistivities was obtained when dykes hydraulic conductivity storativity and effective porosity are respectively about three one and one orders of magnitude lower than the host aquifer the presence of the dykes results in barrier like alterations of groundwater flow and saltwater intrusion preferential flowpaths occur parallel to observed dyke orientations freshwater inflows from upland recharge areas concentrate on the land facing side of the dykes and saltwater penetration is higher on their sea facing side this has major implications for managing groundwater resources in dyke intruded aquifers including in coastal and island regions but also provides wider insights on preferential pathways of groundwater flow and transport in highly heterogeneous aquifer systems this article is protected by copyright all rights reserved

thermodynamically consistent decompression implications for lower mantle composition estimates of the composition of the lower mantle are commonly obtained by a process of adiabatic decompression in which zero pressure mantle parameters are determined with a least squares fit of an equation of state to mantle densities we show that this procedure may lead to biased estimates of the zero pressure density and compressibility of the mantle the bias can be eliminated or minimized by subjecting the equation of state fit to a thermodynamic constraint at zero pressure such inversions provide equations of state that are compatible with the lower mantle as well as the thermal properties of selected mineral models we used this method to evaluate assemblages containing mg fe sio3 perovskite and mg fe o with fe fe mg ratios as high as 0 2 thermodynamic systematics were used to place bounds on the anderson gruneisen parameter s for perovskite we find a fairly large range of acceptable models for the composition of the lower mantle they range from uppermantle like compositions to assemblages that are enriched in both si and fe relative to the upper mantle however a pure perovskite lower mantle whether enriched in fe or not seems improbable small fe enrichments of the order of 1 given density contrasts across the 670 km discontinuity that are probably insufficient to prevent convective mixing of the upper and lower mantles we therefore suggest that unless the mantle is homogeneous in its major oxide components the lower mantle is likely to be enriched in fe by at least several percent

the volcanic evolution of martinique island insights from k ar dating into the lesser antilles arc migration since the oligocene abstract the lesser antilles island arc bifurcates into two lines in its northern part with an old branch to the east and a recent active branch to the west martinique is located at the southern tip of the separation the two arcs diverge northward and at maximum divergence are separated by a 50 km wide depression despite this separation which suggests a jump in volcanism activity has been almost continuous in martinique island with a slow displacement of the eruptive centers to the west considering timing of emplacement previous authors defined three cycles of activity the old intermediate and recent arcs of late oligocene early miocene mid miocene and late miocene to present ages respectively the present study investigates the timing of emplacement of the volcanic units in martinique island in order to constrain the activity of the old and intermediate lesser antilles arcs as recorded on this island unspiked k ar age determinations on groundmass and plagioclase separates cassignol gillot technique were conducted on 20 samples from the old and intermediate volcanic chains martinique has evolved as eight distinct volcanic centers 1 basal complex and sainte anne series 24 8 0 4 20 8 0 4 ma for the old arc 2 vauclin pitault chain 16 1 0 2 8 44 0 12 ma and 3 south western volcanism 9 18 0 16 7 10 0 10 ma for the intermediate arc and 4 morne jacob volcano 5 14 0 07 1 54 0 03 ma 5 trois ilets volcanism 2 358 0 034 ma and 346 27 ka 6 carbet complex 998 14 to 322 6 ka 7 mount conil 543 8 to 127 2 ka and 8 mount pelee 126 2 ka to present for the recent arc germa et al 2010 germa et al 2011a we propose migration rates of 1 1 1 4 km myr westward toward the back arc region throughout the whole volcanic history of martinique island these rates together with geochemical evidence for a more enriched signature in the youngest magmas are consistent with a geodynamic evolution involving the migration of the northern volcanic front away from the trench in response to the subduction of an aseismic ridge possibly influenced by convergence between north american and south american plates

melt segregation from partially molten source regions the importance of melt density and source region size the compressibility of basic melt at 1 atmosphere is about an order of magnitude higher than that of mantle minerals consequently the density contrast between melt and the principal residual crystals in mantle source regions is expected to decrease with increasing source region depth the increasingly olivine normative character of primary melts produced at greater depths is also expected to result in a decrease in this density contrast with increasing source region depth once vertical permeability is established by melt generated during partial melting buoyancy driven melt percolation can under some circumstances segregate melt from the residual crystals in its source region on a geologically rapid time scale limits to this process are provided by cooling of the source region freezing melt in and rigidity of the crystalline matrix mechanically trapping melt source region size influences these limits strongly consequently small partially molten diapirs km in diameter may be able to trap large melt fractions 30 but larger source regions would be unable to do so the reduction in density contrast with pressure reduces the buoyant force driving melt percolation and provides another limit to melt segregation diapirs at depth may thus stably contain large fractions of melt but may decompress and unload their melt during ascent this effect would be enhanced in small diapirs and may be relevant to the genesis of komatiitic magma melt compression may also be a factor in explaining why the very different maximum depths inferred for typical basic melt segregation from source regions on different planets 500 km on the moon 250 km on mars 100 km on earth correspond to similar pressures 25 35 kbar at greater pressures melt may no longer be capable under ordinary conditions of segregating upwards by buoyancy this may also help to explain why depleted peridotites overlie more fertile peridotites and how deep regions of the mantle are able to remain fertile over geologic time

quasi 3d modeling of airborne tem data by spatially constrained inversion we present a new methodology spatially constrained inversion sci that produces quasi 3d conductivity modeling of electromagnetic em data using a 1d forward solution spatial constraints are set between the model parameters of nearest neighboring soundings data sets models and spatial constraints are inverted as one system the constraints are built using delaunay triangulation which ensures automatic adaptation to data density variations model parameter information migrates horizontally through spatial constraints increasing the resolution of layers that would be poorly resolved locally sci produces laterally smooth results with sharp layer boundaries that respect the 3d geological variations of sedimentary settings sci also suppresses the elongated artifacts commonly seen in interpretation results of profile oriented data sets in this study sci is applied to airborne time domain em data but it can also be implemented with other ground based or airborne data types

pathways and distances of fluid flow during low grade metamorphism evidence from pyrite deposits of the cameros basin spain new geochemical and sulphur isotopic data are presented for a number of pyrite deposits from the late jurassic early cretaceous cameros basin spain the deposits were formed at or close to the peak of metamorphism and are always related to sandstone units in the mainly metapelite sequence iron remained immobile and conservative pyrite iron being derived by sulphidation of chlorite in the host metapelites reduced sulphur however was supplied from two external sources thermochemical reduction of sulphate and release of s during metamorphism of sedimentary sulphides these sources provided isotopically heavy and light s respectively with variation in pyrite isotopic composition between different deposits resulting from differences in their relative importance at each site during metamorphism the sandstone units acted as aquifers carrying the sulphidic pore waters to locations where permeability provided by syn depositional fractures on a scale of 0 5 5 m allowed its interaction with the metapelites transport distances for sulphide during metamorphism were of the order of hundreds of metres

the core shadow zone boundary and lateral variations of the p velocity structure of the lowermost mantle abstract the recent determination of high quality short period p wave amplitude profiles near the core shadow zone for three source receiver combinations allows an exploration of lateral variations in p velocity structure at the base of the mantle various radially symmetric models are tested by comparison of the data with amplitudes measured from generalized ray theory synthetics the assumption necessary to justify one dimensional modeling that each of the profiles is most sensitive to scales of heterogeneity larger than the discrete regions sampled is well supported by the coherence of the individual profiles the observed amplitude versus distance profiles exhibit significant regional variations of the apparent shadow zone boundary with as much as a 5 shift in onset distance but it is possible to model the overall behavior using simple regionally varying positive p velocity gradients in the lowermost mantle velocity models with pervasive negative velocity gradients in the d layer are not consistent with the data the modeling indicates that d velocities beneath the north pole are 2 slower than those beneath the central pacific while velocities beneath the north pacific are 1 faster although the simplest class of successful models begins to deviate from the prem reference earth model as much as 690 km above the core mantle boundary these models do not violate global mantle velocity constraints and the theoretical slowness values calculated for the three models are consistent with slowness measurements for the same general regions more complex multiple gradient lower mantle velocity structures with a thinner zone of lateral heterogeneity may be compatible with the p wave data but such detailed structures cannot be resolved by our modeling though bounds can be placed on viable structures the strong lateral variations required by the data support the presence of compositional heterogeneity in d and the data require that at least in several locations the predominant p velocity gradients in d are positive

timing of diagenesis and very low grade metamorphism in the eastern sector of the sierra de cameros iberian range spain a u pb shrimp study on monazite the sierra de cameros is an intracontinental orogen and represents the north western part of the iberian range in northern spain it comprises a thick sequence of syn rift continental sediments mainly sandstones and carbonates deposited during lower cretaceous times a unique characteristic of the sierra de cameros in relation to the rest of the iberian range is the presence of low grade metamorphism in certain parts of the basin an event that predates basin inversion this paper describes the presence textural relationships and geochemical aspects of authigenic and or metamorphic monazite within different lithologies from the deepest parts of the basin sensitive high resolution ion microprobe shrimp u pb dating of monazite records the presence of two age populations the first with 206 pb 238 u ages ranging from 122 to 116 ma which is considered as diagenetic in origin whilst the second is dated at 99 2 ma and postdates the metamorphic climax

chemical stratification in the silicate earth abstract the largest density contrast between magmas and common ferromagnesian minerals in the mantle occurs at two locations these are nearest the earth s surface and at about 650 700 km depth where the lower mantle mineral assemblage becomes stable at solidus temperatures the large density contrast between magmas and olivine nearest the surface diminishes to zero somewhere between the middle and lower stratigraphic sections of the upper mantle it is also here where the composition of all anhydrous magmas is most similar to that of an undepleted garnet iherzolite composition for an earth that has differentiated by fractional crystallization and melting processes which depend on the separation of crystalline phases from silicate liquids having different densities the 650 km discontinuity could represent a chemical boundary layer the chemical change in the early archean could have been from primordial upper mantle compositions above the boundary layer to differentiated lower mantle compositions below a primary stratigraphic model is offered for the distribution of depleted enriched and primordial isotopic mantle components formed by the transport fate of magmas in the beginning of earth history depleted morb source regions were established in the uppermost part of the upper mantle primordial mantle was located at the middle to the deepest regions of an upper mantle which was processed by anhydrous melting and crystallization enriched and depleted components could have been formed at these levels also by igneous processing in the presence of h 2 o or co 2 and involving highly compressible magmas the lower mantle became heterogeneous with enrichments at the top and depletions elsewhere it is suggested that the present day isotopic structure of the mantle has inherited elements of this primary stratification primordial 143 nd 144 nd and 87 sr 86 sr observed in oceanic islands basalts are located in the middle of upper mantle convection cells enriched ratios found in both oceanic islands basalt and kimberlite could have originated near and on either side of the 650 km chemical boundary layer

melting temperature distribution and fractionation in the lower mantle abstract the melting curve of perovskite mgsio3 and the liquidus and solidus curves of the lower mantle were estimated from thermodynamic data and the results of experiments on phase changes and melting in silicates the initial slope of the melting curve of perovskite mgsio3 was obtained as d t m d p 77 k gpa 1 at 23 gpa the melting curve of perovskite was expressed by the kraut kennedy equation as t m k 917 1 29 6 v v 0 where tm 2900 k and p 23 gpa and by the simon equation p gpa 23 21 2 t m k 2900 1 75 1 the liquidus curve of the lower mantle was estimated as t liq 0 9 t m perovskite and this gives the liquidus temperature tliq 7000 500 k at the mantle core boundary the solidus curve of the lower mantle was also estimated by extrapolating the solidus curve of dry peridotite using the slope of the solidus curve of magnesiowustite at high pressures the solidus temperature is 5000 k at the base of the lower mantle if the temperature distribution of the mantle was 1 5 times higher than that given by the present geotherm in the early stage of the earth s history partial melting would have proceeded into the deep interior of the lower mantle estimation of the density of melts in the mgo feo sio2 system for lower mantle conditions indicates that the initial melt formed by partial fusion of the lower mantle would be denser than the residual solid because of high concentration of iron into the melt thus the melt generated in the lower mantle would tend to move downward toward the mantle core boundary this downward transportation of the melt in the lower mantle might have affected the chemistry of the lower mantle such as in the d layer and the distribution of the radioactive elements between mantle and core

structure of the earth mantle and core the deep interior structure of the earth has been extensively analyzed using a wide variety of seismic phases and techniques during the last four years most studies have emphasized quantitative three dimensional mapping of the lateral velocity heterogeneity of the mantle and core these aspherical velocity variations are believed to be direct manifestations of thermal and compositional heterogeneity associated with convective processes a first generation of global models for the lateral velocity variations in the deep earth has been produced providing tantalizing images of large scale structures suggestive of a non steady state thermal convection system the upper 400 km of the mantle has the strongest lateral velocity variations of up to 10 for shear velocity surface wave analyses that do not require a priori regionalizations have demonstrated that there is a strong association between surface tectonic provinces and the uppermost mantle velocity variations thus the thermal and convective state of the upper 200 km of the mantle can be reliably interpreted in the context of plate tectonics the upper mantle models support the contention that continents have deep roots with differences in velocity structure from oceanic and active tectonic regions extending as deep as 400 km very long wavelength lateral velocity variations of a few percent have been detected in the transition zone at depths from 400 to 670 km as well as throughout the lower mantle these deep seated variations have little correspondence to surface tectonics and efforts to interpret their nature are just beginning the lowermost 200 km of the mantle d region has lateral velocity fluctuations comparable to those in the upper mantle and evidence has been presented for the presence of a sizable velocity discontinuity at the top of the d layer a combined thermal and compositional boundary layer roughly mirroring the lithosphere is a likely explanation for this anomalous zone the core mantle boundary appears to have significant 10 km long wavelength topography presumably sustained by dynamic stresses from deep mantle convection the inner core may have strong lateral heterogeneity or axially symmetric anisotropy suggesting a complex thermal and compositional state significant progress has been made in characterizing the frequency dependence of anelastic attenuation in the mantle in the short period body wave band models for teleseismic p wave attenuation operators have converged with t values of 0 7 1 0 s appropriate at 1 hz and t values of 0 4 0 6 s appropriate at 4 hz regional variations of attenuation are slowly being mapped out as well

conceptual hydrogeological model and aquifer system classification of a small volcanic island la gomera canary islands abstract conceptual groundwater models in volcanic island aquifers remain an issue in many regions of the world this study takes advantage of the large number of outcrops exposing the inner structure of la gomera canary islands due to its inactivity during the last 2 5 ma to develop a conceptual groundwater model that helps improving groundwater resource management in the island and increasing knowledge in volcanic aquifers based on a volcanostratigraphic model five hydrostratigraphic units have been defined that include two main aquifers and volcaniclastic deposits located between them that control the vertical movement of the groundwater the island has been classified into four aquifer systems or water management units based on their hydrogeological features that permit a sustainable and independent management of the resources of one aquifer system in relationship with the other ones the consideration of the complexity and heterogeneity of la gomera geology has allowed to develop a conceptual groundwater flow model and to identify four general groundwater situations 1 groundwater in the upper aquifer discharging to the sea 2 groundwater in the upper aquifer springing out along the main ravines 3 groundwater in the basal aquifer impounded by dikes and 4 groundwater in the basal aquifer discharging to the sea

sandstone petrography of continental depositional sequences of an intraplate rift basin western cameros basin north spain the cameros basin in central spain is an intraplate rift basin that developed from late jurassic to middle albian time along nw se trending troughs the sedimentary basin fill was deposited predominantly in continental environments and comprises several depositional sequences these sequences consist of fluvial sandstones that commonly pass upward into lacustrine deposits at the top producing considerable repetition of facies this study focused on the western sector of the basin where a total of seven depositional sequences ds 1 to ds 7 have been identified the composition of sandstones permits the characterization of each sequence in terms of both clastic constituents and provenance in addition four main petrofacies are identified petrofacies a is quartzosedimentolithic mean of qm85f2lt13 and records erosion of marine jurassic pre rift cover during deposition of fluvial deposits of ds 1 brezales formation petrofacies b is quartzofeldspathic mean of qm81f14lt5 with p f 1 at the base this petrofacies was derived from the erosion of low to medium grade metamorphic terranes of the west asturian leonese zone of the hesperian massif during deposition of ds 2 jaramillo formation and ds 3 salcedal formation quartzose sandstones characterize the top of ds 3 mean of qm92f4lt4 petrofacies c is quartzarenitic mean of qm95f3lt2 with p f 1 and was produced by recycling of sedimentary cover triassic arkoses and carbonate rocks in the sw part of the basin ds 4 pen acoba formation finally depositional sequences 5 6 and 7 pinilla de los moros hortiguela pantano and abejar castrillo de la reina formations respectively contain petrofacies d this petrofacies is quartzofeldspathic with p f near zero and a very low concentration of metamorphic rock fragments from qm85f11lt4 in pantano formation to qm73f26lt1 in castrillo de la reina formation petrofacies d was generated by erosion of coarse crystalline plutonics located in the central iberian zone of the hesperian massif in addition to sandstone petrography these provenance interpretations are supported by clay mineralogy of interbedded shales thus shales related to petrofacies a and c have a variegated composition illite kaolinite and randomly interlayered illite smectite mixed layer clays the presence of chlorite characterizes interbedded shales from petrofacies b and illite and kaolinite are the dominant clays associated with petrofacies d these petrofacies are consistent with the depositional sequences and their hierarchy an early megacycle consisting of petrofacies a and b ds 1 to ds 3 was deposited during the initial stage of rifting when troughs developed in the west asturian leonese zone a second stage of rifting resulted in propagation of trough bounding faults to the sw involving the central iberian zone as a source terrane and producing a second megacycle consisting of petrofacies c and d ds 4 ds 5 ds 6 and ds 7 sandstone composition has proven to be a powerful tool in basin analysis and related tectonic inferences on intraplate rift basins because of the close correlation that exists between depositional sequences and petrofacies

static compression and olivine flotation in ultrabasic silicate liquid piston cylinder techniques have been used to observe static compressions of ultrabasic silicate liquids to 6 gpa and 2000 c compressions are measured by bracketing sinking and floating of olivine crystals of known density at run conditions komatiite peridotite and their liquid mixtures with fe2sio4 all show constant density changes with pressure of 0 07 g cm3 gpa along their liquidi these results confirm shock wave studies and ultrasonic studies which show weak compositional effects on compressibility of basic to ultrabasic silicate liquid the techniques converge in supporting the conjecture of stolper et al 1981 that ultrabasic silicate liquids may be denser than their equilibrium coexisting olivines and pyroxenes at high compressions the pressure of this density inversion is 7 8 gpa for the compositions studied olivine flotation provides an important constraint upon earth evolution models that include extensive melting during early differentiation it also provides a mechanism for concentrating high mg si olivine in the upper mantle without unduly perturbing other geochemical parameters a full evaluation of the physical and geochemical consequences is required at an early date