Provenance discrimination of Paleozoic mudstones within a contact metamorphic aureole determined by REE, Th, and Sc analyses, Sierra Nevada, California

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

OSTI ID:5129904

Yoshinobu, A S; Hanson, A D; Girty, G H ^[1]; Knaack, C; Johnson, D ^[2]

---

1. San Diego State Univ., CA (United States). Dept. of Geological Sciences
2. Washington State Univ., Pullman, WA (United States). Dept. of Geology

REE, Th, and Sc analyses of samples collected from the Lower Paleozoic Shoo Fly Complex (SFC), northern Sierra terrane, support the hypothesis that the structurally lowest portion of the SFC (i.e., the Lang, Black Oak Spring, and Zion Hill sequences) is primarily composed of continentally derived detritus. Fifteen samples collected from mudstones in and adjacent to the contact aureole of the Middle Jurassic Emigrant Gap composite pluton vary in metamorphic grade from chlorite [+-] white mica slaty argillites outside of the aureole to K-feldspar [+-] sillimanite phyllitic schists adjacent to the pluton. On chondrite-normalized REE distribution diagrams, the samples exhibit (1) no systematic change as a result of increasing contact metamorphic grade, (2) LREE enrichment trends, and (3) Eu anomalies ranging from 0.46 to 0.93, and averaging 0.66. These REE characteristics are like those documented for passive margin turbidites and Post Archean Average Shale (PAAS), and suggest that contact metamorphism did not significantly alter REE distribution. On a La-Th-Sc ternary diagram the authors data cluster in the fields of passive continental margin and PAAS. The average Th/U ratio is 8.8 which strongly implies a recycled and/or weathered source. These new data, coupled with the quartz-rich nature of interbedded sandstones, the absence of volcanic material, and previously determined Precambrian detrital zircon ages suggest that clastic detritus within the Lang, Black Oak Spring, and Zion Hill sequences was derived form a cratonal source which may have been the North American continent.

• OSTI ID: 5129904
• Report Number(s): CONF-9305259-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALIFORNIA
GEOLOGIC FORMATIONS
GEOCHEMISTRY
ORIGIN
SHALES
GEOLOGY
ISOTOPE DATING
METAMORPHISM
RARE EARTHS
SCANDIUM
SIERRA NEVADA COLORADO
THORIUM
ZIRCON
ACTINIDES
AGE ESTIMATION
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
METALS
MINERALS
MOUNTAINS
NORTH AMERICA
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
TRANSITION ELEMENTS
USA
580000* - Geosciences