New York State Museum Bulletin Volume 203-204

New York State Museum Bulletin Volume 203-204

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ...the region is the anortlzosite, which exhibits two rather well-defined, mappable facies. Of these, the Marcy anorthosite is usually very coarse grained, bluish gray, and highly feldspathic, though locally developed gabbroid facies are common. It makes up the greater bulk of the anorthosite, which occupies most of the northeastern half of the quadrangle. The other facies, known as Whiteface anorthosite, is usually medium grained, light gray, and more or less gabbroid. This is a broader development of the Marcy anorthosite. Many small and large inclusions of anorthosite, chiefly the Whiteface type, occur in the syenite-granite series as far out as 7 or 8 miles from the main body of the anorthosite. Next in order of age is the syenite-granite series, which is clearly intrusive into both the Grenville and the anorthosite. It is wholly confined to the southwestern half of the quadrangle where the granite facies is the most prominent of all the rocks. A rock type of particular interest, called the Keene gneiss, is well developed, and observations within the quadrangle have thrown much light upon its origin. The two largest bodies mapped each occupy several square miles. This Keene gneiss is considered to have resulted from the actual digestion or assimilation of anorthosite by the syenite-granite magma.. Gabbro stocks of the usual Adirondack kind are prominently developed in the southwestern half of the quadrangle, but none occur within the great body of anorthosite. Each of the two stocks covers several square miles. Pegmatite and diabase dikes, both later than the gabbro, are moderately represented. Also a few dikes of aplite occur, some of them younger than the gabbro and some probably older. A small area of dolomitic limestone has long more

Product details

  • Paperback
  • 189 x 246 x 8mm | 259g
  • United States
  • English
  • black & white illustrations
  • 1236966236
  • 9781236966230