GEOLOGY OF THE ELKHORN MOUNTAINS, NORTHEASTERN OREGON: PART 2. WILLOW LAKE INTRUSION

Abstract

Research Article| September 01, 1960 GEOLOGY OF THE ELKHORN MOUNTAINS, NORTHEASTERN OREGON: PART 2. WILLOW LAKE INTRUSION WILLIAM H TAUBENECK; WILLIAM H TAUBENECK DEPARTMENT OF GEOLOGY, OREGON STATE COLLEGE, CORVALLIS, OREGON; DEPARTMENT OF GEOLOGY, COLUMBIA UNIVERSITY, NEW YORK 27, NEW YORK Search for other works by this author on: GSW Google Scholar ARIE POLDERVAART ARIE POLDERVAART DEPARTMENT OF GEOLOGY, OREGON STATE COLLEGE, CORVALLIS, OREGON; DEPARTMENT OF GEOLOGY, COLUMBIA UNIVERSITY, NEW YORK 27, NEW YORK Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM H TAUBENECK DEPARTMENT OF GEOLOGY, OREGON STATE COLLEGE, CORVALLIS, OREGON; DEPARTMENT OF GEOLOGY, COLUMBIA UNIVERSITY, NEW YORK 27, NEW YORK ARIE POLDERVAART DEPARTMENT OF GEOLOGY, OREGON STATE COLLEGE, CORVALLIS, OREGON; DEPARTMENT OF GEOLOGY, COLUMBIA UNIVERSITY, NEW YORK 27, NEW YORK Publisher: Geological Society of America Received: 26 May 1959 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1960, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1960) 71 (9): 1295–1322. https://doi.org/10.1130/0016-7606(1960)71[1295:GOTEMN]2.0.CO;2 Article history Received: 26 May 1959 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation WILLIAM H TAUBENECK, ARIE POLDERVAART; GEOLOGY OF THE ELKHORN MOUNTAINS, NORTHEASTERN OREGON: PART 2. WILLOW LAKE INTRUSION. GSA Bulletin 1960;; 71 (9): 1295–1322. doi: https://doi.org/10.1130/0016-7606(1960)71[1295:GOTEMN]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Willow Lake intrusion is funnel-shaped with contacts inclined inward at 60°-70° and has a sheetlike appendage to the southwest, inclined northwest at 50°. The pluton lies athwart the southern contact of the Bald Mountain batholith and was emplaced before the main batholithic phases. It contains normal metagabbroic rocks, rhythmically layered rocks similar to those described from the Stillwater and Skaergaard intrusions, and abnormal banded rocks in which the minerals are elongated and arranged with their longer axes at high angles to the banding. Similar abnormal banded rocks have been found in a number of localities in Oregon and California, invariably in steep-walled intrusions of small size, including dikes a foot or less in width. The Willow Lake type of rhythmical layering cannot have been formed by a process combining gravitative sedimentation of crystals with convection currents in the magma, such as accounts for Skaergaard-type layered rocks. The Willow Lake-type layered rocks probably formed by undercooling and crystallization in the oversaturated (metastable) region, combined with intermittent convective and turbulent currents, in a magma near a univariant condition.Banded rocks of this type may be expected in epizonal metamorphic regions in steep-walled mafic intrusions, emplaced late in the regional metamorphic cycle. Criteria for so-called gravity stratification are examined; the various features of density stratification may in part be due to processes other than those operating under the influence of gravity. The perpendicular feldspar rock of the Skaergaard intrusion and the harrisite structure of layered periodotites from the island of Rhum are cited as products of moderate undercooling of magma in a bivariate condition. Translation-gliding effects and a set of conjugate shears developed in Willow Lake banded rocks are attributed to stresses in the crystal mush resulting from magma movements past surfaces of crystallization. The role of diffusion in the interstitial melt is discussed, and the formation of mono-mineralic layers in the Willow Lake banded rocks is attributed to diffusion between interstitial melts of adjacent bands of contrasting mineralogy and reactions between the melts and the surrounding solid phases. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.