Sulfide enrichment along igneous layer boundaries in the lower oceanic crust: IODP Hole U1473A, Atlantis Bank, Southwest Indian Ridge

Reactive porous or focused melt flows are common in crystal mushes of mid-ocean ridge magma reservoirs. Although they exert significant control on mid-ocean ridge magmatic differentiation, their role in metal transport between the mantle and the ocean floor remains poorly constrained. Here we aim to improve such knowledge for oceanic crust formed at slow-spreading centers (approximately half of present-day oceanic crust), by focusing on specific igneous features where sulfides are concentrated. International Ocean Discovery Program (IODP) Expedition 360 drilled Hole U1473A 789 m into the lower crust of the Atlantis Bank oceanic core complex, located at the Southwest Indian Ridge. Coarse-grained (5–30 mm) olivine gabbro prevailed throughout the hole, ranging locally from fine- (<1 mm), to very coarse-grained (>30 mm). We studied three distinct intervals of igneous grain size layering at 109.5–110.8, 158.0–158.3, and 593.0–594.4 meters below seafloor to understand the distribution of sulfides. We found that the layer boundaries between the fine- and coarse-grained gabbro were enriched in sulfides and chalcophile elements. On average, sulfide grains throughout the layering were composed of pyrrhotite (81 vol.%; Fe1-xS), chalcopyrite (16 vol.%; CuFeS2), and pentlandite (3 vol.%; [Ni,Fe,Co]9S8), which reflect paragenesis of magmatic origin. The sulfides were most commonly associated with Fe-Ti oxides (titanomagnetites and ilmenites), amphiboles, and apatites located at the interstitial positions between clinopyroxene, plagioclase, and olivine. Pentlandite exsolution textures in pyrrhotite indicate that the sulfides formed from high-temperature sulfide liquid separated from mafic magma that exsolved upon cooling. The relatively homogenous phase proportion within sulfides along with their chemical and isotopic compositions throughout the studied intervals further support the magmatic origin of sulfide enrichment at the layer boundaries. The studied magmatic layers were likely formed as a result of intrusion of more primitive magma (fine-grained gabbro) into the former crystal mush (coarse-grained gabbro). Sulfides from the coarse-grained gabbros are Ir-Platinum Group Element-rich (PGE; i.e., Ir, Os, Ru) but those from the fine-grained gabbros are Pd-PGE-rich (i.e., Pd, Pt, Rh). Notably, the sulfides from the layer boundaries are also enriched in Pd-PGEs, and therefore elevated sulfide contents at the boundaries were likely related to the new intruding melt. Because S concentration at sulfide saturation level is dependent on the Fe content of the melt, sulfide crystallization may have been caused by FeO loss, both via crystallization of late-precipitating oxides at the boundaries, and by exchange of Fe and Mg between melt and Fe-bearing silicates (olivine and clinopyroxene). The increased precipitation of sulfide grains at the layer boundaries might be widespread in the lower oceanic crust, as also observed in the Semail ophiolite and along the Mid-Atlantic Ridge. Therefore, this process might affect the metal budget of the global lower oceanic crust. We estimate that up to ∼20% of the Cu, ∼8% of the S, and ∼84% of the Pb of the oceanic crust inventory is accumulated at the layer boundaries only from the interaction between crystal mush and new magma. © 2022 The Author

Rocznik Lubuski (t.32, cz.1): Dziedzictwo kulturowe Środkowego Nadodrza

Pod redakcją: Wojciecha Eckerta

Zastosowanie geodezyjnych metod pomiarowych w badaniach nośności pali

Tyt. z nagłówka.Bibliogr. s. 98-[99].Dostępny również w formie drukowanej.STRESZCZENIE: Tradycyjne metody pomiarowe przemieszczeń pali w trakcie próbnych obciążeń mogą być obarczone błędami systematycznymi. Błędy te wynikają najczęściej z przemieszczenia bazy pomiarowej spowodowanego przez deformację podłoża wokół pala obciążanego, przemieszczenia pali kotwiących lub wpływy termiczne. Zastosowanie geodezyjnych metod badania przemieszczeń (w tym niwelacji precyzyjnej) zapewnia niezależny pomiar przemieszczeń badanego pala i zarazem bieżącą kontrolę wyciągania pali kotwiących. Mimo że pomiar geodezyjny jest mniej dokładny od pomiaru czujnikami przemieszczeń, to stanowi cenne narzędzie bieżącej kontroli i weryfikacji. W pracy przedstawiono wybrane przykłady zastosowania metod geodezyjnych w próbnych obciążeniach osiowych i bocznych. SŁOWA KLUCZOWE: próbne obciążenie, geodezyjne badania przemieszczeń. ABSTRACT: Conventional measurement of pile settlement during pile load test may be affected by ground movement due to displacements of anchor piles. The application of direct leveling of high precision enables to provide an independent reference measurement which is free from systematic errors. However this method is less accurate than the use of displacement sensors but provides good results. Some case studies of the use of geodetic methods in vertical and horizontal pile load testing were presented in the paper. KEYWORDS: pile load test, geodetic survey of displacement

Zastosowanie metod estymacji odpornej w obliczeniach nośności granicznej pali

Tyt. z nagłówka.Bibliografia s. 265.Dostępny również w formie drukowanej.ABSTRACT: This work presents the results of the calculations of foundation pile load failure on the basis of the so-called 80%-method, formulated by Brinch Hansen. The approximation procedure has been analysed from the point of view of: the number of measurements of settlements, taken into account in the calculations, the weights of the settlement measurements and the change in the weights of particular settlement measurements (the elimination of errors by the resistant estimation). With the use of Mathcad environment, an algorithm was developed, which serves the calculating of load failure by the following methods: least squares method, when the same weights are assumed for all the analysed points; least squares method, assuming differentiated weights for particular points; Huber method, assuming the initial differentiation of weights; Danish method, with the assumption, that the weights for particular points are initially differentiated. In the computations, one made use of the last six observations in the aspect of elastic-plastic work of piles (the last six observations before the ending of the load test). The conclusions from the calculations are intended to constitute the starting point for the further development of the method of failure load computation on the basis of the results from the static load test, for the needs of calibrations - introduced, with growing frequency, into dynamic load tests. KEYWORDS: pile, load test, failure load, robust estimation. STRESZCZENIE: W pracy przedstawiono wyniki obliczeń nośności granicznej pali fundamentowych na podstawie tzw. metody 80% zaproponowanej przez Brinch Hansena. Przeanalizowano procedurę aproksymacyjną w aspekcie: liczby pomiarów osiadań uwzględnianych w obliczeniach, wag poszczególnych pomiarów osiadań oraz zmiany wag poszczególnych pomiarów osiadań (eliminacja błędów metodami estymacji odpornej). Korzystając ze środowiska Mathcad opracowano algorytm obliczania nośności granicznej następującymi metodami: metodą najmniejszych kwadratów - przy założeniu jednakowych wag dla wszystkich analizowanych punktów; metodą najmniejszych kwadratów - przy założeniu zróżnicowanych wag dla poszczególnych punktów; metodą Hubera - przy założeniu wstępnego zróżnicowania wag dla poszczególnych punktów; metodą duńską - przy założeniu wstępnego zróżnicowania wag dla poszczególnych punktów. W obliczeniach wykorzystywano sześć ostatnich obserwacji z zakresu pracy sprężysto-plastycznej pali (ostatnie sześć obserwacji przed zakończeniem próbnego obciążenia). Wnioski z przeprowadzonych obliczeń mają w dalszych etapach stanowić podstawę do zaproponowania metody obliczania nośności granicznej na podstawie wyników próbnego obciążenia statycznego dla potrzeb kalibracji wdrażanych coraz częściej badań dynamicznych. SŁOWA KLUCZOWE : pal, próbne obciążenie, nośność graniczna, estymacja odporna

Pomiary przemieszczeń pionowych jako ważny aspekt kształcenia geodetów

The rapid development of industry, the automation of production, processing, and mining processes increasingly put more demands on the scope and accuracy of geodetic surveying. Obtaining precise data on the spatial location of objects involved in the production process is indispensable for the efficient management of that process. Registered changes in the geometry of objects may indicate potential threats that may adversely affect the safe operation of the given object. One of the most difficult tasks in engineering surveying is the control of displacements and deformations of building objects and their surroundings. This issue is very broad and concerns most industrial facilities, including opencast mines, landslide areas, cooling towers, water dams, as well as securing deep excavations in compact urban development, verticality control of industrial chimneys and wind farms. Each object has its own specific features and requires an individual approach in the field of measuring network design, the selection of an appropriate measurement technique, and systematic geodetic monitoring of displacements. The key aspect is the professional experience of the surveyor – the geodesist who is managing this type of work. Already at the stage of educating future engineers, it is important not only to provide them with appropriate theoretical knowledge, but also to enable them to acquire practical skills. For this reason, science camps have been organized since 2013 as part of the process of educating geodesy and cartography students at the Wrocław University of Science and Technology. The thematic scope of the camps includes the measurement of displacements of a unique engineering structure over 50 meters high, which is the figure of Christ the King of the Universe, located in Świebodzin. Students gain professional experience using the latest measuring instruments: digital precision levels, motorized electronic total stations, GNSS satellite receivers, and laser scanners. The students, who face real-life surveying challenges, gain valuable professional experiences that improve their qualifications and better prepare them for their future work. The article presents science camps as one of the additional forms of educating surveyors. The scope of work performed during the science camp is presented, and the basic measurement techniques are described. Particular attention was paid to the empirical assessment of the accuracy of the results of measurements of vertical displacements performed by students using the precision levelling method. For the measurement data collected over a period of 8 years, the mean levelling errors were calculated on the basis of the analysis of the levelling sections and polygons. The obtained accuracy meets the requirements for measurements performed in order to determine vertical displacements.Szybki rozwój przemysłu, automatyzacja procesów produkcyjnych, przetwórczych czy wydobywczych stawiają coraz większe wymagania odnośnie zakresu i dokładności pomiarów geodezyjnych. Pozyskiwanie precyzyjnych danych o przestrzennej lokalizacji obiektów biorących udział w procesie produkcyjnym jest niezbędne do sprawnego zarządzania tym procesem. Rejestrowane zmiany geometrii obiektów mogą świadczyć o potencjalnych zagrożeniach, które mogą niekorzystnie wpływać na bezpieczną eksploatację obiektu. Jednym z najtrudniejszych zadań w geodezji inżynieryjnej jest kontrola przemieszczeń i deformacji obiektów budowlanych oraz ich otoczenia. Zagadnienie to jest bardzo szerokie i dotyczy większości obiektów przemysłowych, m.in. kopalni odkrywkowych, terenów osuwiskowych, chłodni kominowych, zapór wodnych, zabezpieczania głębokich wykopów w zwartej miejskiej zabudowie, kontroli pionowości kominów przemysłowych i elektrowni wiatrowych. Każdy obiekt ma swoją specyfikę i wymaga indywidualnego podejścia w zakresie projektowania sieci pomiarowej, doboru odpowiedniej techniki pomiarowej i systematycznego prowadzenia geodezyjnego monitoringu przemieszczeń. Kluczowym aspektem jest doświadczenie zawodowe geodety, kierującego tego typu pracami. Już na etapie kształcenia przyszłych inżynierów, ważne jest nie tylko przekazanie odpowiedniej wiedzy teoretycznej, ale również nabycie umiejętności praktycznych. Z tego powodu w procesie kształcenia studentów geodezji i kartografii na Politechnice Wrocławskiej od 2013 roku organizowane są obozy naukowe. Zakres tematyczny obozów obejmuje pomiar przemieszczeń unikalnej konstrukcji inżynierskiej o wysokości ponad 50 m, którą jest figura Chrystusa Króla Wszechświata znajdująca się w Świebodzinie. Studenci nabierają doświadczenia zawodowego stosując najnowsze instrumenty pomiarowe: cyfrowe niwelatory precyzyjne, zmotoryzowane tachimetry elektroniczne, odbiorniki satelitarne GNSS i skanery laserowe. Studenci borykając się z prawdziwymi wyzwaniami pomiarowymi nabierają cennych doświadczeń zawodowych, które podnoszą ich kwalifikacje i lepiej przygotowują do podjęcia pracy zawodowej. W artykule zaprezentowano obozy naukowe jako jedną z dodatkowych form kształcenia geodetów. Przedstawiono zakres prac wykonywanych w trakcie obozu i scharakteryzowano podstawowe techniki pomiarowe. Szczególną uwagę poświęcono empirycznej ocenie dokładności wyników pomiarów przemieszczeń pionowych wykonywanych przez studentów metodą niwelacji precyzyjnej. Dla danych pomiarowych zebranych z 8 lat obliczono błędy średnie niwelacji na podstawie analizy odcinków i poligonów niwelacyjnych. Uzyskana dokładność spełnia wymogi stawiane pomiarom wykonywanym w celu wyznaczania przemieszczeń pionowych

Assessment of surface parameters of VDW foundation piles using geodetic measurement techniques

This article presents in situ research on the side surface of Vor der Wand (VDW) foundation piles using 3D laser scanning and close-range photogrammetry to assess the morphology of pile concrete surface. Contemporary analytical methods for estimation of the bearing capacity of the foundation pile surface require determination of the parameters of the concrete roughness and the model of the surface being formed, which corresponds to the pile technology used. Acquiring these data is difficult due to the formation of piles in the ground and their subsequent work as a structure buried in the ground. The VDW pile technology is one of the widespread technologies of foundation pile used in practice. These piles exhibit a specific configuration of the lateral surface, which is related to the simultaneous use of auger drilling and casing that rotates in opposite directions. Two geodetic techniques most often used to measure the geometry of buildings are terrestrial laser scanning and close-range photogrammetry. To empirically verify the suitability of these two techniques for describing the VDW pile surface parameters, a two-stage field study was performed. In the first stage, the measurements of concrete test surfaces were conducted. This surface was formed in a smooth formwork and its roughness parameters (in accordance with ISO 25178-2: 2012) were calculated and compared with the reference surface. In the second stage, measurements of the secant VDW sheet pile wall protecting the deep excavation were carried out. The roughness parameters of the pile surface were calculated for the selected areas in diverse geotechnical conditions. The original procedure for processing data (obtained using the above techniques) for assessment of roughness parameters of unique concrete surfaces was presented. The conducted research demonstrates that a pulse scanner has very limited usefulness for determination of roughness parameters for very smooth concrete surface; however, the photogrammetry techniques give acceptable results. In regard to the VDW pile surface, the results obtained from both measurement techniques give satisfactory consistency of the roughness parameters. The relative errors of calculated roughness parameters do not exceed 29% (average 12%). The proposed procedure may improve the accuracy of the assumed friction factor between pile surface and soil for assessment of the pile shaft bearing capacity for various pile technologies and soil conditions

Evaluation of Terrestrial Laser Scanner Accuracy in the Control of Hydrotechnical Structures

In many cases of monitoring or load testing of hydrotechnical structures, the measurement results obtained from dial gauges may be affected by random or systematic errors resulting from the instability of the reference beam. For example, the measurement of wall displacement or pile settlement may be increased (or decreased) by displacements of the reference beam due to ground movement. The application of surveying methods such as high-precision levelling, motorized tacheometry or even terrestrial laser scanning makes it possible to provide an independent reference measurement free from systematic errors. It is very important in the case of walls and piles embedded in the rivers, where the construction of reference structure is even more difficult than usually. Construction of an independent reference system is also complicated when horizontal testing of sheet piles or diaphragm walls are considered. In this case, any underestimation of the horizontal displacement of an anchored or strutted construction leads to an understated value of the strut’s load. These measurements are even more important during modernization works and repairs of the hydrotechnical structures

Accuracy Assessment of Semi-Automatic Measuring Techniques Applied to Displacement Control in Self-Balanced Pile Capacity Testing Appliance

Static load tests of foundation piles are the basic method for the designing or verification of adopted design solutions which concern the foundation of a building structure. Preparation of a typical test station using the so-called inverted beam method is very expensive and labor-intensive. The settlement values of the loaded pile are usually recorded using accurate dial gauges. These gauges are attached to a reference beam located in close proximity to the pile under test, which may cause systematic errors (difficult to detect) caused by the displacement of the adopted reference beam. The application of geodetic methods makes it possible to maintain an independent, external reference system, and to verify the readouts from dial gauges. The article presents an innovative instrumentation for a self-balanced stand for the static load test made from a closed-end, double steel pipe. Instead of typical, precise geometric leveling, the semi-automatic measuring techniques were used: motorized total station measurement and terrestrial laser scanning controlled by a computer. The processing of the acquired data made it possible to determine the vertical displacements of both parts of the examined pile and compare displacements with the results from the dial gauges. On the basis of the excess of the collected observations, it was possible to assess the accuracy, which confirmed the usefulness of measuring techniques under study