Enrichment of trace elements in garnet amphibolites from a paleo-subduction zone: Catalina schist, southern California

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90096-3· OSTI ID:6702731

Sorensen, S S ^[1]; Grossman, J N ^[2]

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1. Smithsonian Institution, Washington, DC (USA)
2. Geological Survey, Reston, VA (USA)

The abundance, P-T stability, solubility, and element-partitioning behaviour of minerals such as rutile, garnet, sphene, apatite, zircon, zoisite, and allanite are critical variables in models for mass transfer from the slab to the mantle wedge in deep regions of subduction zones. The influence of these minerals on the composition of subduction-related magmas has been inferred (and disputed) from inverse modelling of the geochemistry of island-arc basalt, or by experiment. Although direct samples of the dehydration + partial-melting region of a mature subduction zone have not been reported from subduction complexes, garnet amphibolites from melanges of circumpacific and Caribbean blueschist terranes reflect high T (>600{degree}C) conditions in shallower regions. Such rocks record geochemical processes that affected deep-seated, high-T portions of paleo-subduction zones. In the Catalina Schist, a subduction-zone metamorphic terrane of southern California, metasomatized and migmatitic garnet amphibolites occur as blocks in a matrix of meta-ultramafic rocks. This mafic and ultramafic complex may represent either slab-derived material accreted to the mantle wedge of a nascent subduction zone or a portion of a shear zone closely related to the slab-mantle wedge contact, or both. The trace-element geochemistry of the complex and the distribution of trace element among the minerals of garnet amphibolites were studied by INAA, XRF, electron microprobe, and SEM.

• OSTI ID: 6702731
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:12; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
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ACTIVATION ANALYSIS
AMPHIBOLITES
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CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
ELECTRON MICROSCOPY
FEDERAL REGION IX
GARNETS
MASS TRANSFER
METAMORPHIC ROCKS
METAMORPHISM
MICROSCOPY
MINERALS
NEUTRON ACTIVATION ANALYSIS
NONDESTRUCTIVE ANALYSIS
NORTH AMERICA
OXYGEN COMPOUNDS
PETROCHEMISTRY
PETROGENESIS
ROCKS
SCANNING ELECTRON MICROSCOPY
SCHISTS
SILICATES
SILICON COMPOUNDS
SUBDUCTION ZONES
TRACE AMOUNTS
USA
X-RAY EMISSION ANALYSIS
X-RAY FLUORESCENCE ANALYSIS