Sr, Nd and Pd isotopic systematics of the Aleutian arc. II. A unified, petrologic model

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6452901

Myers, J D; Frost, C D

Since arc magmas must ascend through a geologically complex region, they may interact with several isotopically distinct rock types. These include; 1) subducted oceanic crust; 2) subducted sediment; 3) ultramafic mantle material; 4) lithospheric oceanic crust; and 5) shallow-level crust. The isotopic characteristics of individual volcanic centers suggest most of these sources contribute to magma evolution but that their relative importance change with time. Since they are derived from partial fusion of subducted oceanic crust and sediment the isotopic characteristics of parental magmas reflect the nature of these end members and the processes affecting them. Thus, the relatively high Sr and Pb isotopic ratios of Aleutian lavas record seawater alteration of oceanic crust and a sediment component, respectively. The significant 87Sr/86Sr variability of parental magmas reflects the heterogeneous nature of crust alteration while the narrower Nd and Pb ranges are produced by fixed crust/sediment ratios (von Drach et al., 1985, CMP) and the insensitivity of these systems to seawater alteration. These characteristics may or may not be maintained during magma ascent. Initially, magmas interact isotopically with the wedge producing significant Sr and Pb isotopic variability. As magmatic evolve, parental liquids remain isochemical. Since 143Nd/144Nd ratios are constant, parental magmas and assimilated material must have similar isotopic ratios or the assimilated materials must have extremely low Nd content. This model may be applicable to other arcs as well as different tectonic settings.

• Research Organization: Univ. of Wyoming, Laramie (USA)
• OSTI ID: 6452901
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400* -- Geochemistry-- (-1989)
ALEUTIAN ISLANDS
ALKALINE EARTH ISOTOPES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
EARTH CRUST
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC MODELS
GEOLOGY
IGNEOUS ROCKS
ISLANDS
ISOTOPE RATIO
ISOTOPES
LAVA
LEAD ISOTOPES
MAGMA
NEODYMIUM ISOTOPES
OCEANIC CRUST
PETROGENESIS
PETROLOGY
QUANTITATIVE CHEMICAL ANALYSIS
ROCKS
STRONTIUM ISOTOPES
SUBDUCTION ZONES
VOLCANIC ROCKS