ill.; "Clay Mineralogy 435 Lehigh University, March 12, 1962" - T.p.; Report title; Includes bibliographical references.
Abstract Present x-ray data supplemented by electron and petro-graphic microscope scans show that Crater Lake clays are nearly all montmorillonite. Possible kaolin is found in cone locations of high clay concentration. This does not appear to be diagenetic. Location and source relations may explain kaolin and varying peak intensities. Introduction Problem Mineralogy of the clay size fraction from recent bottom sediments of Crater Lake was studied. One objective was to determine whether mineralogy of the clay changes with the varying bottom morphology and environments. Another purpose was to determine whether the mineralogy of the clays alters with the different sources of sediment. Source of the clays may be from normal weathering of exposed rocks of the caldera wall, from former ash falls within the basin, and from areas above and below the water that have been altered by secondary sulfataric and fumarolic activity. Setting Crater Lake is less than 76OO years old and may have formed only within the last 1000 years. It occupies the 4,000 foot deep collapse caldera of an extinct composite volcano, Mt. Mazama. Rapid erosion of the steep walls deposits clastic sandy-silty sediments over the generally flat lake bottom. Towards the lake center and on the raised and protected submerged volcanic structures clay sized particles make up to one-third of the sediment. Sediment patches near areas of intense alteration also have a relatively high clay content. Williams (19^2, p. I36) says in the altered areas the ferromagnesian minerals have been converted to serpentine and, to a lesser degree, to chlorite and talc. Where sulfataric action has been intense, the lavas have been converted to masses of milky opal and kaolin (ibid). 1
Abstract Present x-ray data supplemented by electron and petro-graphic microscope scans show that Crater Lake clays are nearly all montmorillonite. Possible kaolin is found in cone locations of high clay concentration. This does not appear to be diagenetic. Location and source relations may explain kaolin and varying peak intensities. Introduction Problem Mineralogy of the clay size fraction from recent bottom sediments of Crater Lake was studied. One objective was to determine whether mineralogy of the clay changes with the varying bottom morphology and environments. Another purpose was to determine whether the mineralogy of the clays alters with the different sources of sediment. Source of the clays may be from normal weathering of exposed rocks of the caldera wall, from former ash falls within the basin, and from areas above and below the water that have been altered by secondary sulfataric and fumarolic activity. Setting Crater Lake is less than 76OO years old and may have formed only within the last 1000 years. It occupies the 4,000 foot deep collapse caldera of an extinct composite volcano, Mt. Mazama. Rapid erosion of the steep walls deposits clastic sandy-silty sediments over the generally flat lake bottom. Towards the lake center and on the raised and protected submerged volcanic structures clay sized particles make up to one-third of the sediment. Sediment patches near areas of intense alteration also have a relatively high clay content. Williams (19^2, p. I36) says in the altered areas the ferromagnesian minerals have been converted to serpentine and, to a lesser degree, to chlorite and talc. Where sulfataric action has been intense, the lavas have been converted to masses of milky opal and kaolin (ibid). 1