A Nd, Sr and O isotopic investigation into the causes of chemical and isotopic zonation in the Bishop Tuff, California

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doi: 10.1016/0012-821X(84)90123-7
Authors:Halliday, A. N.; Fallick, A. E.; Hutchinson, J.; Hildreth, Wes
Author Affiliations:Primary:
Scot. Univ. Res. and React. Cent., Glasgow, United Kingdom
Other:
U. S. Geol. Surv., United States
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 68(3), p.379-391. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:1984
Note:In English. 39 refs.; illus. incl. 2 tables
Summary:The Bishop Tuff represents a single eruption of chemically zoned rhyolitic magma. Six whole rock samples yield initial 87Sr/86Sr of 0.7060-0.7092 and δ18O of 5.9-10.3 per mil. Six constituent sanidines yield smaller ranges of initial 87Sr/86Sr of 0.7061-0.7069 and δ18O of 6.7-7.9. In contrast 143Nd/144Nd ratios for the six whole rocks and two constituent magnetites exhibit negligible variation with a mean of 0.51258±1. These data are used to show that the phenocrysts were precipitated from an already chemically zoned liquid, that the zoning process involved negligible assimilation of, or exchange with, country rocks and that the extreme Sr and O isotopic disequilibria are probably the result of post-eruptive interaction with meteoric water. The parent magma had εNd = -0.9, εSr = +23 and δ18O = 7 per mil and was formed from mantle-derived magmas and/or melts of lower crustal rocks isotopically similar to parts of the Sierra Nevada Batholith. Modified journal abstract. [P.Br.]
Subjects:Alkaline earth metals; Bishop Tuff; Cenozoic; Geochemistry; Igneous rocks; Isotopes; Magmas; Melts; Metals; Nd-144/Nd-143; Neodymium; O-18/O-16; Oxygen; Petrology; Phenocrysts; Pleistocene; Precipitation; Pyroclastics; Quaternary; Rare earths; Sr-87/Sr-86; Stable isotopes; Strontium; Tuff; Volcanic rocks; Zoning; California; United States
Abstract Numbers:85M/0574
Record ID:1984055568
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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