Compositional variations and equilibrium in REE, U and Th acceptor minerals during I-type granite differentiation, Palisade Crest suite, central Sierra Nevada batholith, California

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

OSTI ID:6379530

Sawka, W N; Chappell, B W

The compositionally zoned Tinemaha and McMurry Meadows plutons have been studied to determine the compositional variations which occur in sphene, allanite, zircon, apatite, +/- hornblende and +/- augite. Mineral separates (42) were analyzed by INAA from seven granites and a mafic inclusion. The REE, U and Th contents and the mineral/rock ratio of all phases generally increase with increasing whole rock silica content. In all the granite samples (except one) and in the mafic inclusion, sphene is the predominant site for REE, U and Th. In one sample where sphene is interstitial, hornblende is the major REE site. Sphene exhibits large compositional variations with 2100 to 5800ppm Nd, 25 to 145 ppm Lu, 400 to 1000ppm Th, and 100 to 700ppm Ta. Apatite exhibits large variations in REE (Nd=240 to 1440ppm) and Th (32 to 125ppm). The major compositional variations for zircon are for U (326 to 5610ppm), Th (322 to 6800ppm) and LREE (La=60 to 12000ppm). Hornblende exhibits large variations in REE concentrations (Ce=52 to 214ppm; Yb=1 to 18 ppm). Compositional variations in these minerals can be related to relative variations in the paragenetic sequence and not to either mineral-melt or subsolidus re-equilibration. Indications of the paragenetic sequence of these phases are also preserved in REE zoning (core-rim) of sphene and allanite, determined by both ion and electron microprobes. Therefore, the trace element concentrations of these mineral phases are apparently governed by mineral-melt partitioning during magmatic crystallization and are not subject to significant re-equilibration in the magma or subsolidus.

• Research Organization: Australian National Univ., Canberra
• OSTI ID: 6379530
• 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

050100* -- Nuclear Fuels-- Reserves
Exploration
& Mining
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
AMPHIBOLE
APATITES
CALIFORNIA
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
EQUILIBRIUM
FEDERAL REGION IX
FELDSPARS
GEOCHEMISTRY
GRANITES
HORNBLENDE
IGNEOUS ROCKS
KINETICS
MAGMATISM
MATERIALS
METALS
MINERALOGY
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PARAGENESIS
PHOSPHATE MINERALS
PLUTONIC ROCKS
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RARE EARTHS
REACTION KINETICS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
THORIUM MINERALS
TITANITE
TRANSITION ELEMENT COMPOUNDS
URANIUM MINERALS
USA
VARIATIONS
ZIRCON
ZIRCONIUM COMPOUNDS
ZIRCONIUM SILICATES