Anatexis of garnet amphibolites from a subduction zone metamorphic terrane

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

OSTI ID:6273410

Sorensen, S S; Barton, M D; Ernst, W G

Concomitant rehydration, metasomatism and amphibolitization of eclogite blocks from a mafic/ultramafic complex of the Catalina Schist terrane, southern California, at estimated metamorphic P approx. 8-12 kb, T approx. 600/sup 0/-700/sup 0/C was apparently accompanied by partial melting of some blocks. Mobilizates of An approx./sub 10-20/ plagioclase (PL) +/- zoisite (ZO) + quartz (QZ) + celadonitic (Si approx. 3.3 p.f.u.) white mica (WM) +/- tourmaline range from stringers and dikelets (approx. 1 cm-0.5 m) in migmatitic amphibolite blocks to dikes approx. 30 m x 3 m which intrude the surrounding, locally enstatite + chlorite +/- talc +/- aluminous actinolite +/- anthophyllite-bearing ultramafic matrix. The uniform phase proportions and the coarse-grained (PL to approx. 20 cm) pegmatitic, graphic, and myrmekitic textures displayed by the dikes and dikelets suggest that they crystallized from silicate melts. WM and ZO appear to be magmatic phases. Fe-rich GT is migmatitic portions of blocks exhibits higher Mg/(Mg + Ca) p.f.u. than GT in restitic portions of blocks; rims are richer in Mg than cores. Field relations, microprobe mineral chemistry, and bulk compositions suggest the pegmatites are low fractions of amphibolite-derived partial melt. Abundant fluid inclusions occur in GT, QZ, PL and clinopyroxene. T/sub h/ for primary H/sub 2/O-rich, low salinity L + V inclusions in GT and QZ from a migmatite range from 136-169/sup 0/C; estimates of T limits for entrapment are 530-640/sup 0/C at 8 kb, 650-780/sup 0/C at 10 kb. H/sub 2/O-rich fluids evidently enabled metasomatism, amphibolitization, and anatexis of (originally) eclogitic rocks at the P-T conditions reflected by the metamorphic mineral assemblages.

• Research Organization: Smithsonian Institute, Washington, DC (USA)
• OSTI ID: 6273410
• 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)
ALKALINE EARTH METAL COMPOUNDS
AMPHIBOLE
AMPHIBOLITES
CALIFORNIA
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
CHLORITE MINERALS
ENSTATITE
FEDERAL REGION IX
FELDSPARS
FLUIDS
GARNETS
GEOCHEMISTRY
GEOTHERMAL FLUIDS
HORNBLENDE
INCLUSIONS
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
METAMORPHIC ROCKS
METAMORPHISM
MICA
MINERALOGY
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PETROGENESIS
PYROXENES
QUARTZ
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SUBDUCTION ZONES
USA