Formation of Primitive Clay Precursors on K-Feldspar Under Extreme Leaching Conditions
Kazue Tazaki, W. S. Fyfe, 1985. "Formation of Primitive Clay Precursors on K-Feldspar Under Extreme Leaching Conditions", Proceedings of the International Clay Conference Denver, 1985, Leonard G. Schultz, H. van Olphen, Frederick A. Mumpton
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Perthitic K-feldspar in Brazilian alkaline rocks covered with a thick weathering rind shows evidence for the formation of iron-rich transitional precursors of clay minerals. High-resolution transmission electron microscopy, energy dispersive X-ray analyses (EDX), and electron diffraction patterns clearly show the decomposition of K-feldspar and growth of these transitional products. They occur as long, curled fiber forms or circular forms on the altered feldspar surface. The electron diffraction patterns show diffuse rings at 4.41, 2.65, 1.56, and 1.38 Å, suggesting poor crystallinity or random orientation. These circular structures, typically 150–200 Å in diameter, contain duplicate to quintuplicate 7-, 14-, and 20-Å lattice images. Step scanning EDX analysis shows that the concentrations of Si, Al, and K tend to decrease and Fe increase from unaltered parts to altered parts of the clay precursors. Crystalline halloysite(7Å) appears to form from them.
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Proceedings of the International Clay Conference Denver, 1985
The papers included in this proceedings volume are representative of the research on clays being conducted in all parts of the world at the time of publication. Many of the subjects treated are controversial, and although some ideas expressed may not necessarily represent the views of the editors, the referees, or the publisher, they deserve to be brought to the attention of the international clay community.