Matrix mineralization

THE ORGANIC MATRIX, MINERAL PHASE AND BONE MINERALIZATION... 

Active zones of Fe oxide reduction in soils can be easily recognized as bleached areas showing the grey colour of the matrix minerals after removal of the staining Fe oxides. Such zones can only form where a microbially metabolizable biomass is available, for example in the lower top soil or along roots. In poorly aerated soils with large structural units (e.g. prisms), root mats often develop only at the surface of these units and bleach their surfaces, whereas the interior is still coloured... 

Microscope observations and chemical analyses help locate the Fe oxides in the fabric of matrix soil particles. Single Fe oxide-containing aggregates which appear uniform to the naked eye, may vary appreciably in Fe content and mineralogy (Ford-ham Norrish, 1979). SEM and TEM photos show goethite and hematite crystals in strongly developed soils to be associated in a more or less systematic fashion with flakes of kaolinite, usually the main matrix mineral in such soils (Fig. 16.19 a-c)... 

Another chondrite component is an optically opaque (in thin section) assortment of very fine-grained minerals that fills the spaces between the larger chondrules, refractory inclusions, and metal grains. This material is called matrix. Characterization of matrix minerals is hampered by their tiny particle sizes (as small as 50-100 nm). Moreover, the fine grain sizes, high porosity, and permeability of matrix make it especially susceptible to alteration during later heating or exposure to aqueous fluids. 

Matrix minerals are complex mixtures of silicates (especially olivine and pyroxene), oxides, sulfides, metal, phyllosilicates, and carbonates. The bulk chemical composition of matrix is broadly chondritic, and richer in volatile elements than the other chondrite components. Some chondrules have rims of adhering matrix that appear to have been accreted onto them prior to final assembly of the meteorite. Small lumps of matrix also occur in many chondrites. Presolar grains, described in Chapter 5, occur in the matrix. 

The aqueous fluids formed by melting of ices in asteroids reacted with minerals to produce a host of secondary phases. Laboratory studies provide information on the identities of these phases. They include hydrated minerals such as serpentines and clays, as well as a variety of carbonates, sulfates, oxides, sulfides, halides, and oxy-hydroxides, some of which are pictured in Figure 12.15. The alteration minerals in carbonaceous chondrites have been discussed extensively in the literature (Zolensky and McSween, 1988 Buseck and Hua, 1993 Brearley, 2004) and were most recently reviewed by Brearley (2006). In the case of Cl chondrites, the alteration is pervasive and almost no unaltered minerals remain. CM chondrites contain mixtures of heavily altered and partially altered materials. In CR2 and CV3oxb chondrites, matrix minerals have been moderately altered and chondrules show some effects of aqueous alteration. For other chondrite groups such as CO and LL3.0-3.1, the alteration is subtle and secondary minerals are uncommon. In some CV chondrites, a later thermal metamorphic overprint has dehydrated serpentine to form olivine. 

In these tissues the distribution of vesicles correspond closely to the patterns of matrix mineralization. Furthermore, it has been suggested that crystals of HA are deposited within the vesicles. Subsequently apatite is deposited within the vesicles and upon their surfaces to produce typical modular clusters of mineral. Such morphological observations strongly implicate the matrix vesicles in the formation of apatite crystals (Fig. 9). Once the first crystals are formed, they mineralize further by epitactic crystal growth458. ... 

The only essential components of the mineral deposition mechanism that are fairly certain at this time relate to phosphate. Even for phosphate, alternative mechanisms are proposed, which are not mutually exclusive but probably function in parallel, in the regulation of different aspects of skeletal calcium transport, and to some extent provide redundancy that allows many mineral transport disorders to be survivable. Alkaline phosphatase activity is essential to produce phosphate. Its major substrate is pyrophosphate. In the absence of the alkaline phosphatase, normally highly expressed as an ectoenzyme by osteoblasts, there is little matrix mineralization... 

Coumot-Witmer G, Zingraff J, Plachot JJ, et al. 1981. Aluminum localization in bone from hemodialyzed patients Relationship to matrix mineralization. Kidney Int 20 375-385. 

Three distinct periods of osteoblast differentiation at the genetic level have been identified during in vitro examination of developing osteoblasts after initial adhesion to a surface (1) cell proliferation and extracellular matrix synthesis, (2) extracellular matrix development and maturation, and (3) extracellular matrix mineralization (Stein and Lian, 1993). A schematic of the time course of osteoblast function and synthesis of extracellular matrix proteins on a newly implanted biomaterial is shown in Fig. 6. 

Unlike major elements, which can homogenize at high T via simple interdiffusion and exchange with matrix minerals, trace elements often have different charges than the major elements for which they substitute. These differences are expected to impede diffusion. For example, to maintain charge balance, the P- Si,... 

Trovafloxacin inhibited growth and extracellular matrix mineralization in MC3T3-E1 osteoblast-like cell cultures (12). The ICso was 0.5 pg/ml, which is below clinically achievable serum concentrations. The authors suggested that the clinical relevance of this observation to bone healing in orthopedic patients should be evaluated. 

Electrothermal vaporization. With ETV/ICP-MS, a small amount of solid sample ( lmg) is introduced into a graphite furnace and subjected to a multi-step temperature program for atomization. Additionally, a modifier can be used for thermal stabilization of the analytes or to improve the matrix mineralization. The vapours produced during the vaporization step are transferred into the plasma by argon carrier gas. 

Dawsonite occurs in oil shale as a matrix mineral formed from the lake water as a chemical precipitate in the sediment. Bader and Esch (26) synthesized dawsonite by bubbling CO 2 into a sodium aluminate solution at a pH of 11. As the pH of their solution dropped, dawsonite precipitated. Dawsonite was obtained only when the sodium carbonate to aluminate ratios were higher... 

The Organic Matrix, Mineral Phase, and Bone Mineralisation... 

Intramembranous ossification is responsible for most of the mineralization of the skull, including the maxilla and mandible. It begins with the differentiation and activation of osteoblasts from fibroblast-related precursors within a region of connective tissue that demarcates where the bone will develop. The osteoblasts secrete a nonmineralized protein-rich (osteoid) matrix and, as they move away, the matrix mineralizes (Fig. 9.3a). The periosteum remains uncalcified and contains latent and undifferentiated osteoblasts for bone remodeling. Odontoblasts (Ob) and cementoblasts secrete an osteoid-like matrix similar to that of intramembraneous ossification. 

Fig. 2 Inhibition of matrix mineralization. Alizarin Red-staining (A570 nm) of 21 day cultures of WT VSMC in the presence of p-glycerophosphate. The cells were cultured with 30 pmol/L of the TNAP inhibitor MLS-0038949 and the PH0SPH01 inhibitors MLS-0263839 and MLS-0390838, either alone or combined, as indicated. Calcium deposition in 21 -day VSMC cultures was evaluated by staining cell layers with Alizarin Red...

Note that, in this study, only the mixing of formation water and waste stream was simulated. The formation matrix (minerals in the sandstone) was not part of the simulated groundwater chemical system. Different kinds of models need to be constructed if the solid matrix is included as part of the system (see 8.1). 

FIGURE 9.4 1 Schematic drawing illustrating the leaching of a matrix mineral fragment containing disseminated copper sullide particles. 

FIGURE 9-4-2 Matrix mineral fragment illustrating react ion zone and reacted and unreacted regions. 

FIGURE 9-4-3 Matrix mineral fragment showing pore network and diffusion paths for solubilized metal ions. 

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