On the lamellar texture of grandite garnet from the Kamaishi mine, Iwate Prefecture, Japan

Fine lamellar textures with chemical contrast are found in anisotropic grandite garnet from the skarn at the Kamaishi mine, Iwate Prefecture. The lamellae are charaterized by enrichment of iron; i. e., the compositional difference between lamellae and matrix amounts to 5 to 10 mole % in andradite molecules. In the sections sliced normal to (110) faces of garnet, the development of lamellae showing orientation parallel to (111) nearly normal to the growth zoning paralell to (110) face. Furthermore, the fine compositional bands (parallel to (110) growth zoning) are observed cutting the (111) lamellae clearly. The data cannot confirm that formation of lamellae normal to (110) occurs in subsolidus or not. However, the compositional band parallel to (110) is obviously results of subsolidus decomposition.