The Keweenaw Series of Michigan Volume 6, V. 2 (Paperback)

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. 1911 Excerpt: ... 15186. Hole 4 at 434 feet from surface. Fine grained microlitic porphyrite; trichitic and the phenocrysts whose dimensions are given have trichitic additions.. Distance from margin 0. Grain Olivine 5; 7; 5; 13 Feldspar 15x4; 43x6; 35x6, av..93x.16 mm. 434-450; (Ss. 15187-8). Amygdaloid; porphyritic texture, (16) (309) which is common in the other amygdaloids, with copper, laumontite and prelmite. Compare Osceola amygdaloid. Sp. 15187. Hole 4 at 438 feet from surface. Like 15186 but coarser. Grain. Olivine 7; 5; 7; 6; 3; 7; 6; 15; 5, av. 0.20 mm. Feldspar 12x2; 30x6; 20x3, av..62x.11 mm. Augite 0. Sp. 15188. Hole 4 at 450 feet from surface. Microlitic porphyritic brecciated. There may be a contact of two flows? Distance from margin 450. Gra n Olivine 4; 7; 4; 5; 5; 5, av. 0.l5 mm. Feldspar 20x4; 40x7; 30x5, av..90x.16 mm. Augite 0. 1. 450-605J; (Ss. 15189-96). Melaphyre, ophite; very feld-(152) (461) spathic; the bottom of bed not reached at the end of the hole, but the grain has become finer, indicating that we are close to the foot. With this flow we pass to drill hole No. V, and the latter must overlap unless the dip is 20, or unless there is a fault of about 150 feet. With a dip of 13 we should expect to find No. V, 0 feet, at No. IV, 436 feet; if the dip is 14, then at No. IV, 462 feet, etc. But the ophites around the top of No. V are judging either from their thickness as measured in the section, which might be affected by the numerous seams in No. V, or from the coarseness of grain, not as thick as the bottom flow in No. IV. Nor are they quite as feldspathic. The bottom of No. V, though it lies in a fissure, and the record cannot be made out clearly, is in coarse feldspathic ophite, which corresponds both to the bottom of No. IV and also to the top o...