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Analcite-bearing intrusives from South Park, Colorado

Jahns, Richard H. (1938) Analcite-bearing intrusives from South Park, Colorado. American Journal of Science, 36 (211). pp. 8-26. ISSN 0002-9599.

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Sills and dikes of analcite diabase and analcite syenite occur as low ridges on the flat floor of South Park, Colorado. The intrusions appear in Cretaceous shaly sandstone, and are probably Laramide in age. Certain features suggest a composite nature for the larger bodies, with the syenitic rock having been injected into pre-existing, but not yet completely solid diabase. Both types contain analcite, some of which is pyrogenetic. At least three mineral reaction series are well shown; all point to crystallization of an alkaline and water-rich magma at low temperatures, with development of a highly sodic residual liquid. The lack of any apparent break between the pyrogenetic and hydrothermal stages suggests for this rock a genetic nature tending in its end stages toward that of veins.

Item Type:Article
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Additional Information:© 1938 American Journal of Science.
Issue or Number:211
Record Number:CaltechAUTHORS:20191104-111658590
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Official Citation:Richard Henry Jahns. Analcite-bearing intrusives from South Park, Colorado. Am J Sci July 1, 1938 Series 5 Vol. 36:8-26; doi:10.2475/ajs.s5-36.211.8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99651
Deposited By: Tony Diaz
Deposited On:04 Nov 2019 21:06
Last Modified:04 Nov 2019 21:06

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