第43回ジオダイナミクスセミナー
　　　Geodynamics　Seminar

要　旨
　The cuboids (fibrous crystals of cubic habit) are one of the most attractive diamond populations. In this topic the mineralogical, chemical, physical and isotopic observations will be reviewed. The genetic application of these data is combined to consider the present concepts of their formation. Fibrous structure of cuboids reflects instability of convex shape and transformation of crystals into dendrite. Dendritic growth leads to mass capture of diamond-forming medium as numerous micro-inclusions. These micro-inclusions contain polyphase assemblage of daughter minerals (quartz, phyllosilicates, carbonates, apatite, etc.) and fluid component (water, carbon dioxide and brines). It was previously registered that compositions of mantle fluids trapped in fibrous diamonds vary between two end members: carbonatitic and hydrous. There are many evidences that cuboids and fibrous diamond coats have genetic link with kimberlites. By summing the most consistent concept is an intrusion of oxidized fluids preceded kimberlitic magma which give rise to formation of cuboids due to reaction with reduced lithosphere.


　　　　　　　　問い合わせ先：山崎　大輔 　TEL　　　（089）927-8408
　　　 　　　　　　　　　　　　　　　 　　 E-mail　　yamazaki@sci.ehime-u.ac.jp