現生および化石こけ虫の骨格 : その化学組成について

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After the brief introduction on the morphology, taxonomy, phylogeny and ecology of the cheilostome bryozoans, the chemical compositions such as minerals, elemental and isotopic compositions of some bryozoan skeletons were discussed. Bryozoan skeletons are composed of three types of mineral phases, namely, high-Mg calcite, high-Sr aragonite and/or their mixtures.<BR>Based on the partition coefficient-ionic radius diagrams for bryozoan skeleton system, three groups of elements can be clarified as follows:(1) Group of Mg, Ca and Sr, only controlled by the crystal structure, they are carbonates, (2) Group of Mn, Fe, Zn, Co, Cu and Ni, controlled by the crystal structure and physiological activities, they are “bio-minerals”, and (3) Group of Li, Na, K, Al, V and Cr, not controlled by the crystal structure, they may be treated as inclusions and foreign detrital grains. The diagrams indicate that the bryozoan skeleton is to be the primitive calcification group formed under the nonequili-brium condition. The elemental composition of mineralizing solution, from which the skeleton of the bryozoan <I>Microporina</I> precipitate, was estimated using the two-step model for elemental partition among skeleton, mineralizing solution and environmental water based on the diagram. The elemental composition of the early Pleistocene bryozoan skeletons was also compared with the Recent one on the standpoint of early diagenetic process.<BR>Both carbon and oxygen isotope compositions of bryozoan skeletons are systematically changed by the water temperature and oxygen isotope composition of seawater.
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現生および化石こけ虫の骨格 : その化学組成について

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