Magma mixing and mingling on Deer, Niblack, and Etolin Islands, southeastern Alaska

Conference · Mon Mar 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5505759

Lindline, J; Crawford, W A; Crawford, M L ^[1]

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1. Bryn Mawr Coll., PA (United States). Geology Dept.

Intimately associated 20 m.a. hornblende-biotite granites and olivine gabbro norites occur on Etolin, Niblack and Deer Islands, southwest of Wrangell, Alaska. The field relationships suggest multiple injections of mafic and felsic phases within this igneous complex. Ellipsoidal to angular mafic magmatic enclaves occur in the granite, ranging in number from sparse to tightly packed swarms. Slightly curved decimeter sized rafts of fine grained mafic enclaves comprise a frozen fountain of mafic magma in the felsic host. Course-grained felsic dikes containing gabbroic zenoliths and ubiquitous fine-grained mafic pillows exhibiting sharp and sutured chilled borders intrude the layered gabbro. Synplutonic northeast trending fine-grained mafic and fine-grained felsic dikes mutually cross-cut the felsic pillow-bearing dikes. The granite consists of green hornblende, dark brown biotite, plagioclase and quartz. The mafic mineral assemblage changes from olivine, orthopyroxene, clinopyroxene, and plagioclase in the gabbro through intermediate-grained phases containing altered clinopyroxene, brown hornblende, red-brown biotite, plagioclase and quartz. The increase in proportion of hydrous mafic minerals from the gabbro to the fine-grained mafic enclaves and changes in pleochroic colors of biotite and hornblende from the intermediate-grained phases to the fine-grained mafic enclaves suggest chemical interaction between the mafic enclaves and their felsic host.

• OSTI ID: 5505759
• Report Number(s): CONF-9303211-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:2; Conference: 28. annual Geological Society of America (GSA) Northeastern Section meeting, Burlington, VT (United States), 22-24 Mar 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALASKA
GEOLOGIC DEPOSITS
GABBROS
PETROGENESIS
PETROLOGY
GRANITES
BIOTITE
FELDSPARS
HORNBLENDE
ISLANDS
MAGMA
MAGMATISM
MINERALOGY
OFFSHORE SITES
OLIVINE
PACIFIC OCEAN
PYROXENES
AMPHIBOLE
DEVELOPED COUNTRIES
GEOLOGY
IGNEOUS ROCKS
MICA
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCKS
SEAS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SURFACE WATERS
USA
580000* - Geosciences