Keweenawan metamorphism

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Journal Article
Journal: Economic Geology
Published: 01 November 1974
Economic Geology (1974) 69 (7): 1118–1125.
...Wayne T. Jolly Abstract Both copper and zinc were mobilized during prehnite-pumpellyite facies metamorphism in the Keweenawan basalts of northern Michigan. Cu, averaging 70 ppm in basalts, was leached from epidotized or more highly metamorphosed rocks in the zone of dehydration; it was introduced...
Journal Article
Journal: GSA Bulletin
Published: 01 August 1943
GSA Bulletin (1943) 54 (8): 1211–1226.
...GEORGE M. SCHWARTZ Abstract The basalts and rhyolites of the Keweenawan of Minnesota have been invaded by the huge mass of the Duluth gabbro as well as by a great number of smaller sills, dikes, and irregular intrusives, mainly diabase. Close to the contact the flows are generally altered to fine...
Series: GSA Memoirs
Published: 01 January 1982
DOI: 10.1130/MEM156-p83
... Keweenawan sedimentary rocks of the Lake Superior region consist of four major sequences: pre-volcanic sedimentary rocks, interflow sedimentary rocks, and post-volcanic sedimentary rocks consisting of the Oronto Group and equivalents and the overlying Bayfield Group and equivalents...
Journal Article
Journal: AAPG Bulletin
Published: 01 December 1967
AAPG Bulletin (1967) 51 (12): 2351–2380.
.... The Black Hills are the culmination of the long north-northwest-trending basement high that includes the Chadron and Cambridge arches of Nebraska and the Central Kansas uplift. Most wells to basement have penetrated metamorphic rocks along this uplift. A granite batholith underlies the area along...
FIGURES | View All (16)
Journal Article
Published: 01 April 2000
The Canadian Mineralogist (2000) 38 (2): 319–344.
... contact-metamorphic aureoles up to 10 m wide containing the assemblages Cal–Tr–Fo and Cal–Di–Fo ( Sutcliffe 1991 ). Rocks of the Keweenawan Supergroup were deposited in and marginal to the Midcontinent rift at approximately 1100 Ma ( e.g., Sutcliffe 1991 ) ( Fig. 1 ), with the main period...
FIGURES | View All (7)
Journal Article
Journal: GSA Bulletin
Published: 01 June 1997
GSA Bulletin (1997) 109 (6): 683–697.
...S. Th. Schmidt; D. Robinson Abstract The 8-km-thick, Keweenawan metabasaltic, North Shore Volcanic Group in Minnesota shows a continuous zeolite to greenschist facies progression through five zonal divisions. Mafic phyllosilicates are ubiquitous and a well-developed smectite-corrensite-chlorite...
Journal Article
Published: 01 July 1993
Canadian Journal of Earth Sciences (1993) 30 (7): 1404–1414.
Journal Article
Published: 01 May 1975
Canadian Journal of Earth Sciences (1975) 12 (5): 821–835.
...Gilbert N. Hanson Abstract The 40 Ar/ 39 Ar method using stepwise heating has been applied to 11 Precambrian mafic rocks in Minnesota and Ontario to test the technique on samples varying from extremely altered to essentially unaltered and to date some of the Lower and Middle Keweenawan igneous...
Journal Article
Journal: GSA Bulletin
Published: 01 December 1955
GSA Bulletin (1955) 66 (12): 1455–1488.
... rocks, especially in the iron formations and the graywackes and slates, and in the post-Huronian basic intrusive rocks, occurred during a post-Huronian-pre-Keweenawan interval of orogeny and minor granite intrusion. At least one earlier period of major, intense metamorphism of pre-Huronian age (Algoman...
Journal Article
Published: 01 August 1969
Canadian Journal of Earth Sciences (1969) 6 (4): 555–568.
... at depths of about 10 km beneath Lake Superior. Amphibole-bearing volcanics, hitherto unreported, were sampled in the basal parts of the Keweenawan extrusive sequence, and represent a higher grade of regional metamorphism than commonly found in the Portage Lake Series. Since metamorphic grade appears...
Book Chapter

J. Kalliokoski
Series: GSA Memoirs
Published: 01 January 1982
DOI: 10.1130/MEM156-p147
... Keweenawan. Similar sandstones in the subsurface in the Michigan Basin are probably Keweenawan, but their precise correlation with the Jacobsville remains uncertain. A lower age limit for the sandstone is established from large basalt clasts derived probably from the Portage Lake Volcanics, and from...
Journal Article
Published: 01 June 1968
Canadian Journal of Earth Sciences (1968) 5 (3): 715–724.
... have been applied to samples from a number of the metasedimentary formations in the region. The ages, however, appear to be the time of folding or of metamorphism rather than of deposition for which only limits or ranges can be given from the ages for associated igneous and metamorphic rocks.Although...
Journal Article