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Title: Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California

Abstract

The Boyden Cave pendant is subdivided into an eastern sequence, chaotic unit, and western sequence. The western sequence has an outcrop width of about 2.5 km and consists of a metasandstone unit, calcsilicate schist unit, andalusite biotite schist unit, and marble unit all metamorphosed to amphibolite grade. Because of complex structural relationships, the stratigraphic thicknesses of these four units are unknown. Psammites within the metasandstone unit, on average, are composed of 85.5 [+-] 4.2% quartz, 8.1 [+-] 4.6% total feldspar, 4.8 [+-] 2.8% white mica, 1.4 [+-] 1.3% biotite, and 0.1 [+-] 0.2% epidote (N = 17). The authors analyzed 10 mudstone samples for major, trace, and REEs from the metasandstone and andalusite biotite schist units of the Boyden Cave pendant. Chondrite-normalized REE distribution patterns exhibit LREE-enrichment trends, and Eu anomalies that vary from 0.61 to 0.86, and average 0.69. Such patterns are characteristic of mudstones composed of continentally derived detritus and are consistent with the complete absence of volcanic material. A similar set of geochemical data was collected from the proposed correlative miogeoclinal units in the Nopah Range, SE California. REE distribution patterns for mudstones from the Stirling Quartzite Wood Canyon Formation, and Carrara Formation exhibit LREE-enrichment trends andmore » Eu anomalies that vary from 0.65 to 0.75, and average 0.68. REE distribution patterns for samples collected from the Boyden Cave and Nopah Range are nearly identical in all aspects. On a La-Th-Sc diagram, data from the mudstones in the Boyden Cave pendant cluster with data from the Nopah Range. Thus, the authors conclude that their data are consistent with the proposed correlations suggested by R.A. Schweickert and M.M. Lahren, and that the western sequence of the Boyden Cave pendant may represent a displaced fragment of the Cordilleran miogeocline.« less

Authors:
;  [1]
  1. San Diego State Univ., CA (United States). Dept. of Geological Sciences
Publication Date:
OSTI Identifier:
5024185
Report Number(s):
CONF-9305259-
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 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; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ARGILLITE; GEOCHEMISTRY; PETROLOGY; CALIFORNIA; GEOLOGIC DEPOSITS; METAMORPHIC ROCKS; CHEMICAL COMPOSITION; OROGENESIS; RARE EARTHS; SCANDIUM; SIERRA NEVADA COLORADO; TECTONICS; THORIUM; ACTINIDES; CHEMISTRY; DEVELOPED COUNTRIES; ELEMENTS; GEOLOGY; METALS; MOUNTAINS; NORTH AMERICA; ROCKS; SEDIMENTARY ROCKS; SHALES; TRANSITION ELEMENTS; USA; 580000* - Geosciences

Citation Formats

Hanson, A D, and Girty, G H. Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California. United States: N. p., 1993. Web.
Hanson, A D, & Girty, G H. Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California. United States.
Hanson, A D, and Girty, G H. 1993. "Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California". United States.
@article{osti_5024185,
title = {Tectonic implications of REE, Th, and Sc analyses of metamorphosed mudstones, Boyden Cave roof pendant, Sierra Nevada, California},
author = {Hanson, A D and Girty, G H},
abstractNote = {The Boyden Cave pendant is subdivided into an eastern sequence, chaotic unit, and western sequence. The western sequence has an outcrop width of about 2.5 km and consists of a metasandstone unit, calcsilicate schist unit, andalusite biotite schist unit, and marble unit all metamorphosed to amphibolite grade. Because of complex structural relationships, the stratigraphic thicknesses of these four units are unknown. Psammites within the metasandstone unit, on average, are composed of 85.5 [+-] 4.2% quartz, 8.1 [+-] 4.6% total feldspar, 4.8 [+-] 2.8% white mica, 1.4 [+-] 1.3% biotite, and 0.1 [+-] 0.2% epidote (N = 17). The authors analyzed 10 mudstone samples for major, trace, and REEs from the metasandstone and andalusite biotite schist units of the Boyden Cave pendant. Chondrite-normalized REE distribution patterns exhibit LREE-enrichment trends, and Eu anomalies that vary from 0.61 to 0.86, and average 0.69. Such patterns are characteristic of mudstones composed of continentally derived detritus and are consistent with the complete absence of volcanic material. A similar set of geochemical data was collected from the proposed correlative miogeoclinal units in the Nopah Range, SE California. REE distribution patterns for mudstones from the Stirling Quartzite Wood Canyon Formation, and Carrara Formation exhibit LREE-enrichment trends and Eu anomalies that vary from 0.65 to 0.75, and average 0.68. REE distribution patterns for samples collected from the Boyden Cave and Nopah Range are nearly identical in all aspects. On a La-Th-Sc diagram, data from the mudstones in the Boyden Cave pendant cluster with data from the Nopah Range. Thus, the authors conclude that their data are consistent with the proposed correlations suggested by R.A. Schweickert and M.M. Lahren, and that the western sequence of the Boyden Cave pendant may represent a displaced fragment of the Cordilleran miogeocline.},
doi = {},
url = {https://www.osti.gov/biblio/5024185}, journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 25:5,
place = {United States},
year = {Thu Apr 01 00:00:00 EST 1993},
month = {Thu Apr 01 00:00:00 EST 1993}
}

Conference:
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