Pelletising of Hematite Ores

Sintering of iron ore fines is assuming great importance in the field of the world's iron and steel industry. This fact depends chiefly: (a) upon necessity of treatment and concentration of lower grade ores,with consequent production of fine concentrates. (b) Upon development of beneficiation techniques, which allow to use ores that up toa few years ago were of no commercial importance (c)Upon advantages shown by burden preparation for blast furnace requiring the separation of fines from the charge. Most of such fines is sintered in DwightLloyd type contiuous grate machines, that hold the first place in sintering ferrous fines. For some time there has been a growing offer of very fine ores, i.e. magnetite concentrates, fine pyrite cinders, flotation concentrates and flotation tailings whose treatment in usual sintering plants pose consi-derable difficulties

Strain improvement and strain maintenance revisited. The use of actinoplanes teichomyceticus atcc 31121 protoplasts in the identification of candidates for enhanced teicoplanin production

Multicellular cooperation in actinomycetes is a division of labor-based beneficial trait where phenotypically specialized clonal subpopulations, or genetically distinct lineages, perform complementary tasks. The division of labor improves the access to nutrients and optimizes reproductive and vegetative tasks while reducing the costly production of secondary metabolites and/or of secreted enzymes. In this study, we took advantage of the possibility to isolate genetically distinct lineages deriving from the division of labor, for the isolation of heterogeneous teicoplanin producer phenotypes from Actinoplanes teichomyceticus ATCC 31121. In order to efficiently separate phenotypes and associated genomes, we produced and regenerated protoplasts. This approach turned out to be a rapid and effective strain improvement method, as it allowed the identification of those phenotypes in the population that produced higher teicoplanin amounts. Interestingly, a heterogeneous teicoplanin complex productivity pattern was also identified among the clones. This study suggests that strain improvement and strain maintenance should be integrated with the use of protoplasts as a strategy to unravel the hidden industrial potential of vegetative mycelium

From marginal to axial tidal-strait facies in the Early Pleistocene Siderno Strait

This geological guide presents the description of locations associated with a two-day field trip arranged in relation to the 10th International Congress of Tidal Sedimentology (Tidalites), Matera, Italy. The field guide describes sedimentological features of the largest among a series of tectonically controlled tidal straits that dissected the Calabrian Arc in southern Italy during the Early Pleistocene. The WNW-ESE trending, 50x20 km-wide Siderno Strait connected the Tyrrhenian with the Ionian seas. Due to tidal phase opposition between the two basins, continuous water-mass exchanges occurred through the strait, leading to powerful, bi-directionally flowing tidal currents. Sediments filling the Siderno Strait derived from both fluvial supply from the margins and intra-basinal autochthonous carbonate-factory debris. The main objective of the two-day field trip is to guide the visitor through a cross-section of the ancient strait, starting from one of the margins, ending in the deeper axial zone. The focus during the day one is on strait-margin deltaic fluvial-dominated deposits, shed from the tectonically-controlled, northern border and reworked by tidal currents in their distal reaches (delta front). Erosively-based, 4-5 m-thick pebbly-sandstone strata intercalated with 2-3 m-thick tidally-generated cross strata stack into a ca. 170 m-thick succession, exposed in a series of outcrops progressively located down-current with respect to the inferred entry point to the north. The focus of the day two is a ca. 150-190 m-thick succession consisting of cross-stratified mixed (bioclastic-siliciclastic) deposits, forming a series of WNE-ESE-oriented, elongated ridges that accumulated in the south-eastern axial zone of the Siderno Strait. The selected stops offer panoramic views of exceptionally continuous sections and close-up observations, revealing different scales of depositional architectures and a variety of sedimentary structures and trace fossils that record the development of these tidal sand ridges during the strait lifespan. The interplay between the tectonic uplift of a central bedrock sill and a number of syn-sedimentary faults and high-frequency relative sea-level changes (induced by glacio-eustacy and active tectonics) can be deciphered from the architecture of the tidally-generated cross strata composing the main body of the ridges

Interplay of tidal and fluvial processes in an early Pleistocene, delta-fed, strait margin (Calabria, Southern Italy)

The architecture and morphodynamics of modern and ancient tidal straits and in particular the deposits of strait-margin zones, have been significantly understudied compared to other marginal marine settings, even though many reservoirs in the North Sea and the Norwegian Continental Shelf are developed in narrow grabens or seaways. This paper presents a detailed sedimentological and stratigraphic analysis of an early Pleistocene marginal-marine succession deposited along the northern margin of the Siderno paleostrait (southern Italy). This area represents an excellent case study of sedimentation along a tidal strait margin, interpreted to record the interaction of fluvial and tidal processes. Here, syn-depositional tectonics produced a complex coastal morphology, significantly influencing sedimentation and hydrodynamic processes. Along the strait margin, the emplacement of an isolated tectonic high (Piano Fossati) created a ca. 3.5 km-wide local passageway. This morpho-structural element induced interplays between fluvio-deltaic processes (fed from the northern strait margin) and tidal current reworking (active within the marine strait).The field-based facies analysis reported here documents an initial stage of non-tidal shallow-marine sedimentation across the strait. A subsequent regression caused river-generated hyperpycnal flows and the transfer of large volumes of pebbly and shelly sandstones into deeper water. Tidal currents became amplified in the strait, and, in the delta-front area, they were able to rework river-derived sediments generating large dune fields. Following the local tidal transport pathway, strong tidal currents skewed the delta front (causing it to be asymmetrical) and elongated sand bodies in a direction parallel to the marine strait axis. Differently from the classical tide-influenced deltas in which onshore-offshore tidal flow predominates, coast-parallel deflection and strong asymmetry of delta-front deposits is a typical feature of deltas entering tide-dominated seaways and straits, where strong tidal currents are capable of dispersing large volumes of sand for significant distances along the coast and along the strait axis. This process became progressively enhanced during the following transgression, when tide-modulated currents reworked biocalcarenitic sands over the previous delta deposits, generating southeasterly migrating dunes. At the end of the transgression, strandplain deposits formed in this area. This last stage of sedimentation was followed by a dramatic regional-scale structural uplift, which ended any marine circulation within the strait. This work provides new insights on sedimentation in a tide-dominated strait, and helps to predict sandbody distribution along the strait margin and axis. These findings can be applied to any other setting characterized by a narrow (possibly structurally-confined) basin dominated by tidal currents

Anatomy of a mixed bioclastic–siliciclastic regressive tidal sand ridge: Facies-based case study from the lower Pleistocene Siderno Strait, southern Italy

Sand ridges, a common feature of modern open shelves, reflect persistent currents and sediment availability under recent transgressive conditions. They represent the largest bedforms in the oceans and, as such, can yield information on long-term oceanographic processes. However, there is a limited number of tidal sand ridges documented from the rock record, examples of regressive tidal sand ridges are scarce and studies describing ridges in straits are even more rare. This study analyses a Gelasian succession within a structurally controlled, tide-dominated strait in the Siderno Basin, southern Italy. The strait connected two wider basins, and accumulated sediments reworked by amplified tidal (bi-directional) currents. A series of tidal sand ridges with superimposed dunes developed close to the south-eastern end of the strait, where bathymetry was deeper and flow expansion occurred. One of the best-exposed tidal sand ridges, 65 m thick, crops out along a ca 2 km long cliff. Large-scale, ESE-prograding, seaward-offlapping shingles contain sets of bioclastic–siliciclastic, coarse-grained, cross-stratified sandstones, erosionally overlying upper Pliocene shelf marls and fine-grained sandstones. Cross-strata show angular, tangential and sigmoidal foresets with compound architectures and a SSE migration, i.e. oblique to the main growth direction. Fossil content indicates open-marine conditions. The succession changes abruptly across an erosion surface to non-tidal, highly burrowed mixed siliciclastic–bioclastic fine-grained sandstones, less than 15 m thick. Documented features reflect stages of nucleation, active accretion and abandonment of an individual sand ridge, during a complete cycle of relative sea-level change. The ridge formed during a phase of normal regression, with accretion occurring during an initial highstand and the ensuing falling stage. During the lowstand the ridge was split into several minor bodies by enhanced tidal currents. The ensuing transgression draped the moribund ridge with tabular strata, whereas final highstand shelf sedimentation reworked the top of the underlying sand body with weak currents

Anatomy and origin of authochthonous late Pleistocene forced regression deposits, east Coromandel inner shelf, New Zealand: implications for the development and definition of the regressive systems tract

High-resolution seismic reflection data from the east Coromandel coast, New Zealand, provide details of the sequence stratigraphy beneath an autochthonous, wave dominated inner shelf margin during the late Quaternary (0-140 ka). Since c. 1 Ma, the shelf has experienced limited subsidence and fluvial sediment input, producing a depositional regime characterised by extensive reworking of coastal and shelf sediments during glacio-eustatic sea-level fluctuations. It appears that only one complete fifth-order (c. 100 000 yr) depositional sequence is preserved beneath the inner shelf, the late Pleistocene Waihi Sequence, suggesting any earlier Quaternary sequences were mainly cannibalised into successively younger sequences. The predominantly Holocene-age Whangamata Sequence is also evident in seismic data and modern coastal deposits, and represents an incomplete depositional sequence in its early stages of formation. A prominent aspect of the sequence stratigraphy off parts of the east Coromandel coast is the presence of forced regressive deposits (FRDs) within the regressive systems tract (RST) of the late Pleistocene Waihi Sequence. The FRDs are interpreted to represent regressive barrier-shoreface sands that were sourced from erosion and onshore reworking of underlying Pleistocene sediments during the period of slow falling sea level from isotope stages 5 to 2 (c. 112-18 ka). The RST is volumetrically the most significant depositional component of the Waihi Sequence; the regressive deposits form a 15-20 m thick, sharp-based, tabular seismic unit that downsteps and progrades continuously across the inner shelf. The sequence boundary for the Waihi Sequence is placed at the most prominent, regionally correlative, and chronostratigraphically significant surface, namely an erosional unconformity characterised in many areas by large incised valleys that was generated above the RST. This unconformity is interpreted as a surface of maximum subaerial erosion generated during the last glacial lowstand (c. 18 ka). Although the base of the RST is associated with a prominent regressive surface of erosion, this is not used as the sequence boundary as it is highly diachronous and difficult to identify and correlate where FRDs are not developed. The previous highstand deposits are limited to subaerial barrier deposits preserved behind several modern Holocene barriers along the coast, while the transgressive systems tract is preserved locally as incised-valley fill deposits beneath the regressive surface of erosion at the base of the RST. Many documented late Pleistocene RSTs have been actively sourced from fluvial systems feeding the shelf and building basinward-thickening, often stacked wedges of FRDs, for which the name allochthonous FRDs is suggested. The Waihi Sequence RST is unusual in that it appears to have been sourced predominantly from reworking of underlying shelf sediments, and thus represents an autochthonous FRD. Autochthonous FRDs are also present on the Forster-Tuncurry shelf in southeast Australia, and may be a common feature in other shelf settings with low subsidence and low sediment supply rates, provided shelf gradients are not too steep, and an underlying source of unconsolidated shelf sediments is available to source FRDs. The preservation potential of such autochthonous FRDs in ancient deposits is probably low given that they are likely to be cannibalised during subsequent sea-level falls

Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey

Drilling of intrashelf Miocene clinothems onshore and offshore New Jersey has provided better understanding of their topset and foreset deposits, but the sedimentology and stratigraphy of their bottomset deposits have not been documented in detail. Three coreholes (Sites M27–M29), collected during Integrated Ocean Drilling Program (IODP) Expedition 313, intersect multiple bottomset deposits, and their analysis helps to refine sequence stratigraphic interpretations and process response models for intrashelf clinothems. At Site M29, the most downdip location, chronostratigraphically well-constrained bottomset deposits follow a repeated stratigraphic motif. Coarse-grained glauconitic quartz sand packages abruptly overlie deeply burrowed surfaces. Typically, these packages coarsen then fine upwards and pass upward into bioturbated siltstones. These coarse sand beds are amalgamated and poorly sorted and contain thin-walled shells, benthic foraminifera, and extrabasinal clasts, consistent with an interpretation of debrites. The sedimentology and mounded seismic character of these packages support interpretation as debrite-dominated lobe complexes. Farther updip, at Site M28, the same chronostratigraphic units are amalgamated, with the absence of bioturbated silts pointing to more erosion in proximal locations. Graded sandstones and dune-scale cross-bedding in the younger sequences in Site M28 indicate deposition from turbidity currents and channelization. The sharp base of each package is interpreted as a sequence boundary, with a period of erosion and sediment bypass evidenced by the burrowed surface, and the coarse-grained debritic and turbiditic deposits representing the lowstand systems tract. The overlying fine-grained deposits are interpreted as the combined transgressive and highstand systems tract deposits and contain the deepwater equivalent of the maximum flooding surface. The variety in thickness and grain-size trends in the coarse-grained bottomset packages point to an autogenic control, through compensational stacking of lobes and lobe complexes. However, the large-scale stratigraphic organization of the bottomset deposits and the coarse-grained immature extrabasinal and reworked glauconitic detritus point to external controls, likely a combination of relative sea-level fall and waxing-and-waning cycles of sediment supply. This study demonstrates that large amounts of sediment gravity-flow deposits can be generated in relatively shallow (~100–200 m deep) and low-gradient (~1°–4°) clinothems that prograded across a deep continental shelf. This physiography likely led to the dominance of debris flow deposits due to the short transport distance limiting transformation to low-concentration turbidity currents

Shelf-margin clinothem progradation, degradation and readjustment: Tanqua Depocentre, Karoo Basin (South Africa)

Degradation of basin-margin clinothems around the shelf-edge rollover zone may lead to the generation of conduits through which gravity flows transport sediment downslope. Many studies from seismic-reflection datasets show these features, but they lack small-scale (centimetre to metre) sedimentary and stratigraphic observations on process interactions. Exhumed basin-margin clinothems in the Tanqua depocentre (Karoo Basin) provide seismic-reflection-scale geometries and internal details of architecture with depositional dip and strike control. At the Geelhoek locality, clinothem parasequences comprise siltstone-rich offshore deposits overlain by heterolithic prodelta facies and sandstone-dominated deformed mouth bars. Three of these parasequences are truncated by a steep (6 to 22°), 100 m deep and 1.5 km wide asymmetrical composite erosion surface that delineates a shelf-edge canyon. The fill, from base to top comprises: (i) thick-bedded sandstone with intrabasinal clasts and multiple erosion surfaces; (ii) scour-based interbedded sandstone and siltstone with tractional structures; and (iii) inverse-graded to normal-graded siltstone beds. An overlying 55 m thick coarsening-upward parasequence fills the upper section of the canyon and extends across its interfluves. Younger parasequences display progressively shallower gradients during progradation and healing of the local accommodation. The incision surface resulted from initial oversteepening and high sediment supply triggering deformation and collapse at the shelf edge, enhanced by a relative sea-level fall that did not result in subaerial exposure of the shelf edge. Previous work identified an underlying highly incised, sandstone-rich shelf-edge rollover zone across-margin strike, suggesting that there was migration in the zone of shelf-edge to upper slope incision over time. This study provides an unusual example of clinothem degradation and re-adjustment with three-dimensional control in an exhumed basin margin succession. The work demonstrates that large-scale erosion surfaces can develop and migrate due to a combination of factors at the shelf-edge rollover zone, and proposes additional criteria to predict clinothem incision and differential sediment bypass in consistently progradational systems