Top Of Pile Research Articles

Physical constraints on the migration of immiscible fluids through partially molten silicates, with special reference to magmatic sulfide ores

The migration of dense Fe-rich immiscible liquids through partially molten silicates is of critical importance to several issues including the formation of magmatic sulfide ore deposits and the formation of metallic cores in terrestrial planets. The migration of immiscible dense liquids can be considered to occur in three distinct regimes dictated by the relative sizes of the dense liquid droplets and the crystals making up the silicate crystal mush or partially melted silicate rock. If dense microdroplets are smaller than the diameter of the narrowest portions of pore throats between silicate crystals then downward motion is possible. The maximum rate of downward settling in loosely packed crystal mushes occurs when the droplet size is approximately one tenth the crystal size. As long as the silicate melt between crystals remains, microdroplets are capable of migrating distances of hundreds to thousands of meters vertically through crystal mushes contained in cooling dikes with typical grain sizes. Stranding of larger droplets similar in size to the crystals results from capillary forces preventing droplet deformation as they attempt to pass into pore throats narrower than themselves. Only in very coarse-grained mushes with grain sizes greater than about 2 cm can droplets the size of intergranular pores migrate downwards. On the other hand, coalescence of many microdroplets into pre-existing stranded droplets may generate connected net-textured domains of the dense liquid that are many times larger than the grain size of the mush. When the vertical height of the connected domain is great enough, the pressure gradient inside the dense phase exceeds the capillary force impeding downward motion through narrow pore throats and the immiscible phase is able to move down along vertically-oriented networks. These networks should not suffer stranding until they reach a solid layer or the base of the intrusion. We suggest that, in most cases, sulfide droplets formed by fractional segregation in large magma bodies should come to rest at the top of the crystal pile, whereas sulfides introduced to magmas by assimilation of fine-grained sulfidic sediments should be capable of passing downward through crystal mushes to form massive or net-textured accumulations at the bottom of the partially molten zone.

Approaching hospital administration about adopting cooling technologies

The purpose of this article is to provide intensivists with information and examples regarding cooling technology selection, cost assessment, adaptation, barriers, and presentation to hospital administrators. A review of medical and business literature was conducted using the following search terms: technology assessment, organizational innovation, intensive care, critical care, hospital administration, and presentation to administrators. General recommendations for intensivists are made for assessing cooling technology with descriptions of common new technology implementation stages. A study of 16 hospitals implementing a new cardiac surgery technology is described. A description of successful implementation of an induced hypothermia protocol by one of the authors is presented. Although knowledgeable about the applications of new technologies, including cooling technology, intensivists have little guidance or training on tactics to obtain a hospital administration's funding and support. Intensive care unit budgets are usually controlled by nonintensivists whose interests are neutral, at best, to the needs of intensivists. To rise to the top of the large pile of requisition requests, an intensivist's proposal must be well conceived and aligned with hospital administration's strategic goals. Intensivists must understand the hospital acquisition process and administrative structure and participate on high-level hospital committees. Using design thinking and strong leadership skills, the intensivist can marshal support from staff and administrators to successfully implement cooling technology.

Evolution of minesoils at a coal waste pile: A case study from Rosice-Oslavany (Czech Republic)

Mine soil development at abandoned coal waste pile (Kukla-Vaclav Nosek mine, Oslavany) represents a possibility to study initial stages of pedogenetic process. Seven soil profiles were uncovered by digging pits at the base and on the slopes and top of the waste pile. Several conclusions concerning soil development at waste pile are possible on the basis of soil profiles description and basic chemistry: 1. Intensive humification was the main pedogenetic process in the initial stages of mine soil evolution at the Kukla waste pile. There is no translocation of clay minerals even in the soil profiles evolving for about 60 years; 2. The youngest soil situated on the top of the waste pile has the most stable granular aggregates. The stability of aggregates corresponds to the increased representation of the total organic matter; 3. Humus quality of the present topsoils in the Kukla waste pile is substantially influenced by the biological recultivation.

Differentiation and Compaction in the Skaergaard Intrusion

Igneous differentiation processes are constrained from bulk compositions, densities and mineral modes of 116 cumulate gabbro samples in a new reference profile through the Layered Series of the Skaergaard intrusion, East Greenland. The stratigraphic distribution of P, U and Rb in cumulates and residual magma, modeled by Rayleigh fractionation, constrains the final porosities or trapped liquid contents to 30-52% in LZa troctolites, decreasing to 4-12% at the top of LZb olivine-gabbros and remaining low (1-13%; 4{middle dot}6% on average) in the oxide-gabbros of LZc, MZ and UZ. Local variations in trapped liquid content are associated with modal layering: leucocratic, low-density rocks have higher proportions of trapped melt than adjacent melanocratic, high-density rocks. These observations are explained by varying degrees of compaction. Compaction was most important after the onset of Fe-Ti oxide crystallization because of the high densities of the crystal matrix. Here computed rates of compaction exceed the rate of crystal accumulation in layers that are metres to a few tens of metres thick. In the basal section (LZa) the crystal pile was too thin and the density of the crystal matrix too low to drive the rate of compaction above the high rate of crystal accumulation promoted by initial cooling through the intrusion floor. In the overlying section (LZb) the efficiency of compaction gradually increased as a result of thickening of the crystal pile and lowering of the rate of crystal accumulation. The modeling constrains the P2O5 content of the residual magma to [~]1{middle dot}7 wt % at the level of apatite-in, suggesting that the magma contained [~]49 wt % SiO2 and followed a trend of iron enrichment. Compaction of the uppermost metres to tens of metres of crystal mush at the top of the cumulate pile was an efficient means of differentiation and resulted in layers with variable final porosities and trace element contents depending on the mineralogy and density of the crystal matrix.

Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

New analytical data are presented for 13 enriched high-Ti tholeiitic basalts from the top of the Faroese lava pile that was formed by the time of break-up of the North Atlantic ∼ 56–55 Ma ago and are located on the eastern continental margin of the Atlantic Ocean. The samples fall in three groups according to their Nb/Zr/Y chemistry: High-Ti1, High-Ti2 and High-Ti3. The grouping is related to their stratigraphic position so that the High-Ti1 group is found lowest in the sampled profiles and the High-Ti3 group at the top with the High-Ti2 group in between. The High-Ti1 and High-Ti2 groups have 206Pb/ 204Pb = 17.59–18.30 while the High-Ti3 group has 206Pb/ 204Pb = 18.88–19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land Formation and the High-Ti2 and High-Ti3 groups correlate with the Geikie Plateau Formation and Rømer Fjord Formation, respectively. The discovery of equivalents to the East Greenland Geikie Plateau Formation and Rømer Fjord Formation means that volcanism has proceeded longer than previously thought on the Faroe Islands but with a lot lower intensity than on the other side of the rift. This demonstrates that large parts of the km-thick volcanic successions of the North Atlantic LIP developed in parallel on the juxtaposed rifted continental margins during break-up, although the centre of eruptions moved away from the Faroe Islands during the last stages of volcanism. Pb-isotope ratios indicate that the High-Ti1, High-Ti2, Milne Land Formation and Geikie Plateau Formation have the same mantle source while the High-Ti3 and Rømer Fjord Formation also contain material from another mantle component. High-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may be that High-Ti1 and Milne Land Formation magmas fractionated significant amounts of clinopyroxene at the bottom of the crust before rising to higher crustal levels, whereas High-Ti2 and Geikie Plateau Formation magmas initially fractionated olivine at lower pressures.

The High Deccan duricrusts of India and their significance for the ‘laterite’ issue

In the Deccan region of western India ferricrete duricrusts, usually described as laterites, cap some basalt summits east of the Western Ghats escarpment, basalts of the low-lying Konkan Plain to its west, as well as some sizeable isolated basalt plateaus rising from the Plain. The duricrusts are iron-cemented saprolite with vermiform hollows, but apart from that have little in common with the common descriptions of laterite. The classical laterite profile is not present. In particular there are no pisolitic concretions, no or minimal development of concretionary crust, and the pallid zone, commonly assumed to be typical of laterites, is absent. A relatively thin, non-indurated saprolite usually lies between the duricrust and fresh basalt. The duricrust resembles the classical laterite of Angadippuram in Kerala (southwestern India), but is much harder. The High Deccan duricrusts capping the basalt summits in the Western Ghats have been interpreted as residuals from a continuous (but now largely destroyed) laterite blanket that represents in situ transformation of the uppermost lavas, and thereby as marking the original top of the lava pile. But the unusual pattern of the duricrusts on the map and other evidence suggest instead that the duricrusts formed along a palaeoriver system, and are now in inverted relief. The two interpretations lead to different tectonic histories. Duricrust formation involved lateral material input besides vertical elemental exchange. We may have reached the stage when the very concepts of laterite and lateritization are hindering progress in regolith research.

Mineralogy and chemical composition of VMS deposits of northern Apennine ophiolites, Italy: evidence for the influence of country rock type on ore composition

In the ophiolites of the Italian northern Apennines, mantle rocks were exposed on the seafloor and eroded prior to the extrusion of pillow basalt and the deposition of pelagic sediments. Various types of VMS deposits occur at different stratigraphic positions in the ophiolite sequence. Stockwork-vein and seafloor-stratiform ore bodies are associated with serpentinized mantle peridotite and serpentinite breccia. A second group of sulfide deposits consist of crosscutting stockwork or conformable stratabound ore bodies emplaced into the pillow basalt, and seafloor-stratiform deposits located at the top of the volcanic pile, in contact with the sedimentary cover. Geochemical and mineralogical differences are observed in the ore and gangue assemblages of the deposits that were formed before the outflow of pillow basalt, and those precipitated during and after basalt extrusion. Compared with basalt-hosted sulfide deposits, the ores associated with serpentinite have a higher Cu/Zn ratio due to a low modal proportion of sphalerite and are enriched in the compatible elements Ni, Cr, and Mg. The Co and Ni of the ores reflect those of pyrite. The Co/Ni ratios of pyrite range from 0.29 to 1.79 (av. = 0.74) in serpentinite-hosted deposits and from 1.09 to 8.0 (av. = 2.59) in basalt-hosted deposits. The composition of chlorite varies from Cr-rich, Mg-clinochlore, in serpentinite-hosted deposits, to Fe-clinochlore with relatively high Mn contents, in basalt-hosted deposits. The sulfides in serpentinite contain accessory chromite that is compositionally similar to chromian spinels from abyssal peridotites. The observed geochemical variations among the various ore types are due to the interaction of the ore-forming fluids with different types of country rock (ultramafic vs. mafic), which involves hydrothermal leaching of metals from the substrate, rock-fluid reactions at the site of ore deposition and the mechanical transfer of detrital material from the country rock to the ore forming-system.

A Preliminary Analysis of Microbial and Biochemical Properties of High‐Temperature Compost

We investigated the microbial community of a high-temperature compost process exhibiting an internal temperature exceeding 90 degrees C. The waste pile was crosscut and samples were collected from the bottom to the top of the refuse pile. PCR-denaturing gradient gel electrophoresis analysis suggested that the microbial community of the high-temperature compost is heterogeneous and differs from one locality to another. Heat-stable collagenases and amylases were extracted directly from the compost pile. Collagenases were located in the upper half of the pile, whereas amylases were detected mainly in the lower parts. Several extremely thermophilic strains were isolated at 80 degrees C; these strains were aerobes. Based on 16S rRNA sequence analysis, the isolates clustered together and represent one or two closely related species. We propose that these thermophilic isolates belong to a novel genus, Caldaterra, gen. nov.

Spontaneous formation of dual stratification patterns in a large quasi-two-dimensional sand pile

By pouring a mixture of two types of grains into a large vertical cell with a narrow space, we discovered a dual stratification pattern consisting of two different wavelengths at the upper and lower regions of the resulting sand pile. In the formation of this pattern, we also observed an additional type of kink-a wave that moves toward the top of the sand pile along the slope. The kink, herein called a trapped kink, is essential for the formation of dual stratification patterns. Asymmetric probability distributions are obtained from measurement of the position where the kinks are generated. We proposed a phenomenological model to describe the kink generation process. The results analyzed by this model agree with experimental distributions.

MINERALOGY AND CHEMICAL COMPOSITION OF VMS DEPOSITS OF NORTHERN APENNINE OPHIOLITES, ITALY: EVIDENCE FOR THE INFLUENCE OF COUNTRY ROCK TYPE ON ORE COMPOSITION

In the ophiolites of the Italian northern Apennines, mantle rocks were exposed on the seafloor and eroded prior to the extrusion of pillow basalt and the deposition of pelagic sediments. Various types of VMS deposits occur at different stratigraphic positions in the ophiolite sequence. Stockworkvein and seafloor-stratiform ore bodies are associated with serpentinized mantle peridotite and serpentinite breccia. A second group of sulfide deposits consist of crosscutting stockwork or conformable stratabound ore bodies emplaced into the pillow basalt, and seafloor-stratiform deposits located at the top of the volcanic pile, in contact with the sedimentary cover. Geochemical and mineralogical differences are observed in the ore and gangue assemblages of the deposits that were formed before the outflow of pillow basalt, and those precipitated during and after basalt extrusion. Compared with basalt-hosted sulfide deposits, the ores associated with serpentinite have a higher Cu/Zn ratio due to a low modal proportion of sphalerite and are enriched in the compatible elements Ni, Cr, and Mg. The Co and Ni of the ores reflect those of pyrite. The Co/Ni ratios of pyrite range from 0.29 to 1.79 (av.=0.74) in serpentinite-hosted deposits and from 1.09 to 8.0 (av.=2.59) in basalt-hosted deposits. The composition of chlorite varies from Cr-rich, Mgclinochlore, in serpentinite-hosted deposits, to Feclinochlore with relatively high Mn contents, in basalt-hosted deposits. The sulfides in serpentinite contain accessory chromite that is compositionally similar to chromian spinels from abyssal peridotites. The observed geochemical variations among the various ore types are due to the interaction of the oreforming fluids with different types of country rock (ultramafic vs. mafic), which involves hydrothermal leaching of metals from the substrate, rock-fluid reactions at the site of ore deposition and the mechanical transfer of detrital material from the country rock to the ore forming-system.

GEOLOGICAL SETTING AND STRUCTURAL STYLES OF VOLCANIC MASSIVE SULFIDE DEPOSITS IN THE NORTHERN APENNINES (ITALY): EVIDENCE FOR SEAFLOOR AND SUB-SEAFLOOR HYDROTHERMAL ACTIVITY IN UNCONVENTIONAL OPHIOLITES OF THE MESOZOIC TETHYS

This paper is an overview of the geological setting and structural styles of Cu-sulfide deposits of the VMS-type, associated with Tethyan ophiolites (the Ligurides) in the northern Apennines (Italy). The Italian deposits represent a rare example of VMS associated with both the mantle-peridotite basement and the overlaying volcanic pile, within a single ophiolite sequence. This peculiar feature is due to the particular geodynamic evolution of the Mesozoic Ligurian ocean that allowed the upper mantle to be exposed on the seafl oor for a long period before the outfl ow of MORBtype lava and the deposition of pelagic sediments (cherts, Palombini shales and Calpionella limestones). Middle to Upper Jurassic uprising of the basaltic magma initially provided the heath source for convective circulation of hydrothermal fl uids through the overlaying mantle section, giving rise to sulfi de deposition in crosscutting stockworkveins and seafl oor-stratiform ore bodies within the serpentinized mantle peridotite and the serpentinite breccia formed by submarine erosion of the upper mantle. The setting and structure of VMS associated with the volcanic pile indicate that hydrothermal activity continued during and after the eruption of pillow basalts at the ocean fl oor, forming stockwork veins and conformable stratabound ore bodies within the basalt unit. Furthermore, hydrothermal activity formed seafl oor-stratiform deposits, at the top of the volcanic pile, covered with a thick horizon of cherts containing exhalative deposits of Mn.

Geological setting and structural styles of Volcanic Massive Sulfide deposits in the northern Apennines (Italy): evidence for seafloor and sub-seafloor hydrothermal activity in unconventional ophiolites of the Mesozoic Tethys

This paper is an overview of the geological setting and structural styles of Cu-sulfi de deposits of the VMS-type, associated with Tethyan ophiolites (the Ligurides) in the northern Apennines (Italy). The Italian deposits represent a rare example of VMS associated with both the mantle-peridotite basement and the overlaying volcanic pile, within a single ophiolite sequence. This peculiar feature is due to the particular geodynamic evolution of the Mesozoic Ligurian ocean that allowed the upper mantle to be exposed on the seafl oor for a long period before the outfl ow of MORB-type lava and the deposition of pelagic sediments (cherts, Palombini shales and Calpionella limestones). Middle to Upper Jurassic uprising of the basaltic magma initially provided the heath source for convective circulation of hydrothermal fl uids through the overlaying mantle section, giving rise to sulfi de deposition in crosscutting stockworkveins and seafl oor-stratiform ore bodies within the serpentinized mantle peridotite and the serpentinite breccia formed by submarine erosion of the upper mantle. The setting and structure of VMS associated with the volcanic pile indicate that hydrothermal activity continued during and after the eruption of pillow basalts at the ocean fl oor, forming stockwork veins and conformable stratabound ore bodies within the basalt unit. Furthermore, hydrothermal activity formed seafl oor-stratiform deposits, at the top of the volcanic pile, covered with a thick horizon of cherts containing exhalative deposits of Mn.

Getting to the Top of a Big Pile

Getting to the Top of a Big Pile

Settlement calculation for long-short composite piled raft foundation

The mechanism of long-short composite piled raft foundation was discussed. Assuming the relationship between shear stress and shear strain of the surrounding soil was elasto-plastic, shear displacement method was employed to establish the different explicit relational equations between the load and the displacement at the top of pile in either elastic or elasto-plastic period. Then Mylonakis & Gazetas model was introduced to simulate the interaction between two piles or between piles and soil. Considering the effect of cushion, the flexible coefficients of interaction were provided. With the addition of a relevant program, the settlement calculation for long-short composite piled raft foundation was developed which could be used to account for the interaction of piles, soil and cushion. Finally, the calculation method was used to analyze an engineering example. The calculated value of settlement is 10.2 mm, which is close to the observed value 8.8 mm.

Polyorogenic deformation history recognized at very shallow structural levels: the case of the Antola Unit (Northern Apennine, Italy)

The Antola Unit is a Ligurian Unit occurring at the top of the nappe pile of the Northern Apennines (Italy). Structural analysis indicates that the Antola Unit has been involved in a complex polyphase deformation history developed at a shallow structural level. The successive deformation phases belong to both the Alpine and Apenninic orogenic cycles. Therefore the Antola Unit is a good example of a polyorogenic tectonic unit deformed at a very shallow structural level. The older part of the structural evolution is assigned to the Meso-Alpine tectonic stage and consists of two deformation phases (D1 and D2) characterized by opposite tectonic transport directions. The D1 and D2 structures were sealed by the middle Eocene-Miocene deposits of the Tertiary Piedmont Basin. The younger part of the deformation history instead can be referred to the Northern Apennines tectonics, and consists of two phases (D3 and D4) both involving the Tertiary Piedmont Basin succession. The structural data indicate that the D1 deformations developed in mostly unlithified rocks, and that these structures can be related to the westward emplacement of the Antola Unit in the Alpine orogenic wedge. The D2 phase is characterized by folds and low-angle extensional faults, and is referable to a gravity-driven deformation. Both the D3 and D4 phases, characterized by folds and thrusts, are due to the compressive regime related to the development of the Northern Apennines.

Numerical Heat and Fluid-Flow Modeling of the Panorama Volcanic-Hosted Massive Sulfide District, Western Australia

Exceptional exposure of the Archean Pilbara block in Western Australia reveals a cross section through an Archean massive sulfide-hosting volcanic succession with underlying subvolcanic intrusion in the Panorama district. A numerical model based on available detailed geologic information has been constructed to simulate heat and fluid flow in the Panorama district. The modeling provides insight into the evolution of the hydrothermal system and evaluates key geologic parameters and their influence on fluid-flow, hydrothermal circulation, and the genesis of massive sulfide orebodies. The model simulates important aspects of the Panorama massive sulfide district, such as temperature distribution, relative alteration zonation, and the size and distribution of orebodies. Predicted temperatures ranging from 150oC at the top of the volcanic pile to ~400oC at the andesite-diorite interface are comparable to temperature estimates based on previously published oxygen isotope mapping. Modeled fluid discharge temperatures are highest for the Sulphur Springs deposit (300o–400oC) and lower for the Kangaroo Caves and other deposits (250o–350oC). The most favorable conditions to reproduce the orebodies and their related alteration zonation occur at anisotropic rock permeabilities comparable to the upper oceanic crust (10–15–10–14 m2) and higher fault permeabilities (10–14–10–13 m2) with a specific fault arrangement similar to that mapped in the field. The 4.6 million metric tons (Mt) Sulphur Springs orebody is predicted to form in less than 5,000 yr, assuming a hydrothermal fluid with seawater salinity, 10 ppm base metal concentration, and a low deposition efficiency (≤10%); other deposits form above the faults under similar conditions. A large range of base metal concentrations in the fluids can account for the known orebodies, but high temperatures (≥250oC) and high-flow velocities (>10–7 m/s) are necessary to produce the observed alteration patterns and distribution of ore deposits. Results indicate that the establishment of a significant hydrothermal system capable of forming economic massive sulfide deposits is favored in fresh volcanic rock packages that have not been affected by earlier compaction or alteration. Under these conditions, economic massive sulfide orebodies (>5 Mt of 10% Zn + Cu) may form in a few thousand years, although the overall lifespan of the hydrothermal system may be between 30,000 and ~200,000 yr, depending on the variations in rock and fault permeability with time.

THE EVOLUTION OF THE LIGURIAN UNITS IN SOUTHERN TUSCANY: A NEW PROPOSAL

To attempt the reconstruction of the stratigraphic – tectonic framework of the oceanic units pertaining to the Ligure – Piemontese Ocean (Ligurian Units Auctt.: Helminthoid Flysch Units, Vara Units, Lanciaia Fm.) cropping out in Southern Tuscany, sedimentological, biostratigraphical, petrographical and structural studies were performed. These analyses were carried out in some key outcrops (Gambassi-Montaione; S. Donato in Poggio; Northern Monti della Gherardesca; Micciano-Libbiano and Serrazzano; Lanciaia-Montecastelli Pisano,). Moreover, field data were integrated with those coming from the geothermal wells. The biostratigraphic and petrographic analyses and the sedimentological observation permit to group the Cretaceous helminthoid flysches of these areas in a single formation, the Monteverdi Marittimo Fm., subdivided in three members: i) Larderello Member deposited in the middle part of the basin,, ii) Montaione Member, deposited in the inner (western?) part and close to an ophiolitic ridge because of the occurrence of ophiolitic olistoliths and breccias iii) San Donato Member, that represents the distal eastern part of the turbiditic system. Despite a complex polyphasic evolution, the piling up of four main Ligurian tectonic units can be recognized (from bottom to top of the pile): Castelnuovo Val di Cecina Unit (CVU), Vara Unit (VU) and Lanciaia Fm., Castelluccio Unit (CU), Montignoso Unit (MU). The Lupicaia Creek Unit (LU) is also present locally at the top of the pile (Montecatini Val di Cecina and south of the Montaione-Gambassi). In the Early and to Late Paleocene, the thrust of the VU onto the Monteverdi M.mo Fm. (CVU) happened and was sealed by the sedimentation of the Lanciaia Fm. which can be considered an earlier Epiligurian unit. Since Late Eocene also the Lanciaia Fm. was deformed by the out-ofsequence thrust of the CU and, finally, of the MU. Preliminary structural data point out to two main tectonic events, at least perpendicular, that affect the Ligurian Units. The first one (axes direction approximately E-W) strongly affects all Ligurian Units while is absent in the Tuscan Units and in the neogenic sediments. On the other hand the second tectonic event (axes direction NW-SE) affect only the Tuscan Unit and the neogenic sediments and refold the first event. In particular, the structural data point out, at least for the Ligurian Units of this sector of the Northern Apennines, to a structural evolution likely linked, until the Middle – Upper Eocene, to a transpressive tectonic context probably focused along the transform fault of the Ligure-Piemontese Ocean.

TECTONO-SEDIMENTARY EVOLUTION OF THE LIGURIAN UNITS IN SOUTHERN TUSCANY

To attempt the reconstruction of the stratigraphic – tectonic framework of the oceanic units pertaining to the Ligure – Piemontese Ocean (Ligurian Units Auctt.: Helminthoid Flysch Units, Vara Units, Lanciaia Fm.) cropping out in Southern Tuscany, sedimentological, biostratigraphical, petrographical and structural studies were performed. These analyses were carried out in some key outcrops (Gambassi- Montaione; S. Donato in Poggio; Northern Monti della Gherardesca; Micciano-Libbiano and Serrazzano; Lanciaia- Montecastelli Pisano,). Data coming from the geothermal wells were also utilized for regional correlation. The Cretaceous helminthoid flysches of these areas have been grouped in a single formation, the Monteverdi Marittimo Fm., subdivided in three members: i) Larderello Member deposited in the middle part of the basin,, ii) Montaione Member, deposited in the inner (western?) part and close to an ophiolitic ridge because of the occurrence of ophiolitic olistoliths and breccias iii) San Donato Member, that represents the distal eastern part of the turbiditic system. Despite a complex polyphasic evolution, the piling up of four main Ligurian tectonic units can be recognized (from bottom to top of the pile): Castelnuovo Val di Cecina Unit (CVU), Vara Unit (VU) and Lanciaia Fm., Castelluccio Unit (CU), Montignoso Unit (MU). The Lupicaia Creek Unit (LU) is also present locally at the top of the pile (Montecatini Val di Cecina and south of the Montaione-Gambassi). Between the Early and the Late Paleocene, the thrust of the VU onto the Monteverdi M.mo Fm. happened and was sealed by the sedimentation of the Lanciaia Fm.. Since Late Eocene also the Lanciaia Fm. was deformed by the out-ofsequence thrust of the CU and, finally, of the MU. In particular, the structural data point out, at least for the Ligurian Units of this sector of the Northern Apennines, to a structural evolution likely linked, until the Middle – Upper Eocene, to a transpressive tectonic context. This regime probably was focused along the transform fault of the Ligure- Piemontese Ocean.

Fissure eruption of flood basalts from statistical analysis of dyke fracture length

Flood basalt emplacement results from eruption of dyke swarms. Several lines of evidence suggest, however, that a large number of dykes in large igneous provinces have never erupted, or have done so over too short a length for any evidence of eruption to be found in the field. We have mapped 1025 dykes and dyke segments from two swarms in western Ethiopia, most of which are of basaltic composition, the others of silicic composition. The dykes cut across the basal breccia of the trap series, and are observed at a structural level c. 1000 m below the current top of the lava pile on the nearby volcanic plateau. We test the hypothesis that at such a depth, some of the basaltic dykes may have erupted whereas some others may not. Due to higher buoyancy within the trap series, silicic dykes are likely to have been systematically eruptive. The area is flat, which has allowed analysis of dyke length distribution at constant structural level, a useful approach for the characterisation of other fracture types such as tension fractures and faults. We found that dyke length follows a power-law distribution. When en échelon dyke segments are counted as single dykes (having as their length the accumulated length of the individual segments), the population exponent, 1.8, is in the mean of the exponents usually obtained for fracture data sets. This exponent correctly fits the shortest dykes considered (1–9 km). A much steeper slope (3.3) is obtained for the distribution of intermediate lengths (9–10 to 10–20 km), and is interpreted as a possible consequence of the eruption of those dominantly basaltic dykes that are more than 9–10 km long at the observed structural depth. The longest, silicic dykes (10–20 to 50 km) have the same population exponent as the shortest, basaltic dykes. This is explained by the homogeneous propagation mode of both populations, either dominantly horizontal or dominantly vertical. However, the silicic dyke population exhibits a slightly larger population coefficient, for which we discuss the possible influence of the Precambrian fabric. Analysis of fracture length distribution appears to be a promising tool for estimating how much of a dyke swarm is eruptive and better understanding the mechanisms of fissure eruption in large igneous provinces.

Study on pile drivability with one dimensional wave propagation theory

Pile drivability is a key problem during the stage of design and construction installation of pile foundations. The solution to the one dimensional wave equation was used to determine the impact force at the top of a concrete pile for a given ram mass, cushion stiffness, and pile impedance. The kinematic equation of pile toe was established and solved based on wave equation theory. The movements of the pile top and pile toe were presented, which clearly showed the dynamic displacement, including rebound and penetration of pile top and toe. A parametric study was made with a full range of practical values of ram weight, cushion stiffness, dropheight, and pile impedance. Suggestions for optimizing the parameters were also presented. Comparisons between the results obtained by the present solution and in-situ measurements indicated the reliability and validity of the method.