ISBN: 9781231062524

RareBooksClub. Paperback. New. This item is printed on demand. Paperback. 250 pages. Dimensions: 9.7in. x 7.4in. x 0.5in.This historic book may have numerous typos and missing text. Pur… Mehr…

RareBooksClub. Paperback. New. This item is printed on demand. Paperback. 250 pages. Dimensions: 9.7in. x 7.4in. x 0.5in.This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. Excerpt: . . . discussed further are as follows (generally from youngest to oldest, or from smallest to largest): 1. Tertiary intrusives (are there two kinds); 2. Tertiary dikes versus Precambrian dikes; 3. Northwest versus northeast porphyry dikes; 4. Pegmatites (are they related to a particular magma series); 5. Mount Ethel and Buffalo Pass plutons, similarities and differences, including (a) accessory fluorite, (b) economic implications; 6. Correlation of Park Range rocks with other igneous rocks of Colorado and Wyoming, including (a) Sherman-Silver Plume dichotomy, (b) mafic dikes. TERTIARY INTRUSIVES Early workers in the Elkhead Mountains along the west side of the Park Range were convinced that there were two series of post-Cretaceous eruptives: an early light-colored acid porphyry and a late dark basalt. Later work in this and adjacent areas has proved that there is more than one age of basalt and that there is really a continuum of compositions from basalt to rhyolite rather than a strictly bimodal assemblage. However, the variation of magma composition with time is as yet incompletely understood, and more data are needed. Within the area of the present report two compositionally distinctive Tertiary intrusive rocks are present, but their relative ages are not known. Also, the spread in their compositions is less than half as great as the compositional spread of the continuum as a whole (fig. 15). Analyzed examples of these two rocks are provided in table 5: sample 22 is from a light-colored Rittmann trachyandesite sill, and sample 19 is from its feeder dike, from within the area shown as Browns Park Formation and post-Browns Park porphyry intrusives in figure 3 east of Clark; sample 226 is from an olivine-containing Rittmann dark latite dike, one of a series cutting. . . This item ships from La Vergne,TN., RareBooksClub<