3D micro-computed tomography of trabecular and cortical bone architecture with application to a rat model of immobilisation osteoporosis

Bone mass and microarchitecture are the main determinants of bone strength. Three-dimensional micro-computed tomogrpahy has the potential to examine complete bones of small laboratory animals with very high resolution in a non-invasive way. In the presented work, the proximal part of the tibiae of hindlimb unloaded and control rats were measured with 3D MicroCT, and the secondary spongiosa of the scanned region was evaluated using direct evaluation techniques that do not require model assumptions. For determination of the complete bone status, the cortex of the tibiae was evaluated and characterised by its thickness. It is shown that with the proposed anatomically conforming volume of interest (VOI), up to an eight-fold volume increase can be evaluated compared to cubic or spherical VOIs. A pronounced trabecular bone loss of −50% is seen after 23 days of tail suspension. With the new evaluation techniques, it is shown that most of this bone loss is caused by the thinning of trabeculae, and to a lesser extent by a decrease in their number. What changes most radically is the structure type: the remaining bone is more rod-like than the control group's bone. Cortical bone decreases less than trabecular bone, with only −18% after 23 day

Microarchitecture and Nanomechanical Properties of Trabecular Bone After Strontium Administration in Osteoporotic Goats

Strontium (Sr) ralenate is a new agent used for the prevention and treatment of osteoporosis. As a bone-seeking element, 98% of Sr is deposited in the bone and teeth after oral ingestion. However, the effect of Sr treatment on bone microarchitecture and bone nanomechanical properties remains unclear. In this study, 18 osteoporotic goats were divided into four groups according to the treatment regimen: control, calcium alone (Ca), calcium and Sr at 24 mg/kg (Ca + 24Sr), and calcium and Sr at 40 mg/kg (Ca + 40Sr). The effects of Sr administration on bone microarchitecture and nanomechanical properties of trabecular bones were analyzed with micro-CT and nanoindentation test, respectively. Serum Sr levels increased six- and tenfold in the Ca + 24Sr and Ca + 40Sr groups, respectively. Similarly, Sr in the bone increased four- and sixfold in these two groups. Sr administration significantly increased trabecular bone volume fraction, trabecular thickness, and double-labeled new bone area. Sr administration, however, did not significantly change the nanomechanical properties of trabecular bone (elastic modulus and hardness). The data suggested that Sr administration increased trabecular bone volume and improved the microarchitecture while maintaining the intrinsic tissue properties in the osteoporotic goat model

High stresses stored in fault zones: example of the Nojima fault (Japan)

During the last decade pulverized rocks have been described on outcrops along large active faults and attributed to damage related to a propagating seismic rupture front. Questions remain concerning the maximal lateral distance from the fault plane and maximal depth for dynamic damage to be imprinted in rocks. In order to document these questions, a representative core sample of granodiorite located 51.3 m from the Nojima fault (Japan) that was drilled after the Hyogo-ken Nanbu (Kobe) earthquake is studied by using electron backscattered diffraction (EBSD) and high-resolution X-ray Laue microdiffraction. Although located outside of the Nojima damage fault zone and macroscopically undeformed, the sample shows pervasive microfractures and local fragmentation. These features are attributed to the first stage of seismic activity along the Nojima fault characterized by laumontite as the main sealing mineral. EBSD mapping was used in order to characterize the crystallographic orientation and deformation microstructures in the sample, and X-ray microdiffraction was used to measure elastic strain and residual stresses on each point of the mapped quartz grain. Both methods give consistent results on the crystallographic orientation and show small and short wavelength misorientations associated with laumontite-sealed microfractures and alignments of tiny fluid inclusions. Deformation microstructures in quartz are symptomatic of the semi-brittle faulting regime, in which low-temperature brittle plastic deformation and stress-driven dissolution-deposition processes occur conjointly. This deformation occurred at a 3.7–11.1 km depth interval as indicated by the laumontite stability domain. Residual stresses are calculated from deviatoric elastic strain tensor measured using X-ray Laue microdiffraction using the Hooke's law. The modal value of the von Mises stress distribution is at 100 MPa and the mean at 141 MPa. Such stress values are comparable to the peak strength of a deformed granodiorite from the damage zone of the Nojima fault. This indicates that, although apparently and macroscopically undeformed, the sample is actually damaged. The homogeneously distributed microfracturing of quartz is the microscopically visible imprint of this damage and suggests that high stresses were stored in the whole sample and not only concentrated on some crystal defects. It is proposed that the high residual stresses are the sum of the stress fields associated with individual dislocations and dislocation microstructures. These stresses are interpreted to be originated from the dynamic damage related to the propagation of rupture fronts or seismic waves at a depth where confining pressure prevented pulverization. Actually, M6 to M7 earthquakes occurred during the Paleocene on the Nojima fault and are good candidates for inducing this dynamic damage. The high residual stresses and the deformation microstructures would have contributed to the widening of the damaged fault zone with additional large earthquakes occurring on the Nojima fault

3D micro-computed tomography of trabecular and cortical bone architecture with application to a rat model of immobilisation osteoporosis

Bone mass and microarchitecture are the main determinants of bone strength. Three-dimensional micro-computed tomogrpahy has the potential to examine complete bones of small laboratory animals with very high resolution in a non-invasive way. In the presented work, the proximal part of the tibiae of hindlimb unloaded and control rats were measured with 3D MicroCT, and the secondary spongiosa of the scanned region was evaluated using direct evaluation techniques that do not require model assumptions. For determination of the complete bone status, the cortex of the tibiae was evaluated and characterised by its thickness. It is shown that with the proposed anatomically conforming volume of interest (VOI), up to an eight-fold volume increase can be evaluated compared to cubic or spherical VOIs. A pronounced trabecular bone loss of −50% is seen after 23 days of tail suspension. With the new evaluation techniques, it is shown that most of this bone loss is caused by the thinning of trabeculae, and to a lesser extent by a decrease in their number. What changes most radically is the structure type: the remaining bone is more rod-like than the control group's bone. Cortical bone decreases less than trabecular bone, with only −18% after 23 day

Mineral Weathering and Metal Leaching under Meteoric Conditions in F-(Ba-Pb-Zn) Mining Waste of Hammam Zriba (NE Tunisia)

Mining waste is an obvious source of environmental pollution due to the presence of heavy metals, which can contaminate soils, water resources, sediments, air, and people living nearby. The F-(Ba-Pb-Zn) deposit of Hammam Zriba located in northeast Tunisia, 8 km southeast of Zaghouan was intensively exploited from 1970 to 1992. More than 250,000 m3 of flotation tailings were produced and stored in the open air in three dumps without any measure of environmental protection. Thus, in this paper, mineralogical and chemical characterization, especially the sulfide and carbonate phases, were carried out to evaluate the potential for acid mining drainage (AMD) and metal leaching (ML). Conventional analytical methods (XRD, XRF, SEM) have revealed that this mining waste contains on average 34.8% barite–celestine series, 26.6% calcite, 23% quartz, 6.3% anglesite, 4.8% fluorite, 2.1% pyrite, and 0.4% sphalerite. The content of sulfides is less important. The tailing leaching tests (AFNOR NFX 31-210 standard) did not generate acidic leachate (pH: 8.3). The acidity produced by sulfide oxidation was neutralized by calcite present in abundance. Furthermore, the leaching tests yielded leachates with high concentrations of heavy metals, above the authorized thresholds. This high mobilization rate in potential toxic elements (PTE) represents a contamination risk for the environment

Mineral Weathering and Metal Leaching under Meteoric Conditions in F-(Ba-Pb-Zn) Mining Waste of Hammam Zriba (NE Tunisia)

International audienceMining waste is an obvious source of environmental pollution due to the presence of heavy metals, which can contaminate soils, water resources, sediments, air, and people living nearby. The F-(Ba-Pb-Zn) deposit of Hammam Zriba located in northeast Tunisia, 8 km southeast of Zaghouan was intensively exploited from 1970 to 1992. More than 250,000 m 3 of flotation tailings were produced and stored in the open air in three dumps without any measure of environmental protection. Thus, in this paper, mineralogical and chemical characterization, especially the sulfide and carbonate phases, were carried out to evaluate the potential for acid mining drainage (AMD) and metal leaching (ML). Conventional analytical methods (XRD, XRF, SEM) have revealed that this mining waste contains on average 34.8% barite-celestine series, 26.6% calcite, 23% quartz, 6.3% anglesite, 4.8% fluorite, 2.1% pyrite, and 0.4% sphalerite. The content of sulfides is less important. The tailing leaching tests (AFNOR NFX 31-210 standard) did not generate acidic leachate (pH: 8.3). The acidity produced by sulfide oxidation was neutralized by calcite present in abundance. Furthermore, the leaching tests yielded leachates with high concentrations of heavy metals, above the authorized thresholds. This high mobilization rate in potential toxic elements (PTE) represents a contamination risk for the environment

Intracrystalline melt migration in deformed olivine revealed by trace element compositions and polyphase solid inclusions

International audienceMelt transport mechanisms have an important impact on the chemical composition of the percolated host rock and the migrating melts. Melt migration is usually assumed to occur at grain boundaries. However, microstructural studies revealed the occurrence of polyphase inclusions along dislocations, subgrain boundaries and microcracks in single mineral grains. The inclusions are interpreted as crystallized melt pockets suggesting that melts can migrate within deformed crystals. Intracrystalline melt migration and diffusive re-equilibration can lead to significant mineral trace element enrichments when associated with dissolution–precipitation reactions. In this contribution, we study a body of replacive troctolites associated with the Erro-Tobbio ophiolitic mantle peridotites (Ligurian Alps, Italy). The replacive formation of the olivine-rich troctolite involved extensive impregnation of a dunitic matrix, i.e. partial dissolution of olivine and concomitant crystallization of interstitial phases. The olivine matrix is characterized by two distinct olivine textures: (i) coarse deformed olivine, representing relicts of the pre-existing mantle dunite matrix (olivine1), and (ii) fine-grained undeformed olivine, a product of the melt–rock interaction process (olivine2). Previous studies documented a decoupling between olivine texture and trace element composition, namely enriched trace element compositions in olivine1 rather than in olivine2, as would be expected from the dissolution–precipitation process. Notably, the trace element enrichments in deformed olivines are correlated with the occurrence of elongated 10 µm size polyphase inclusions (clinopyroxene, Ti-pargasite, chromite) preferentially oriented along olivine crystallographic axes. These inclusions show irregular contacts and have no crystallographic preferred orientation with the host olivine, and the phases composing the inclusions show similar chemical compositions to the vermicular phases formed at the grain boundaries during late-stage reactive crystallization of the troctolite. This suggests that the investigated inclusions did not form as exsolutions of the host olivine but rather by input of metasomatic fluids percolating through the deformed olivine grains during closure of the magmatic system. We infer that strongly fractionated volatile-rich melts were incorporated in oriented microfractures within olivine1 and led to the crystallization of the polyphase inclusions. The presence of intracrystalline melt greatly enhanced diffusive re-equilibration between the evolved melt and the percolated olivine1, in turn acquiring the enriched character expected in neoformed olivine crystals. Intracrystalline melt percolation can have strong geochemical implications and can lead to efficient re-equilibration of percolated minerals and rocks