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Geochemistry of the stable isotopes of silicon

Abstract

One hundred thirty two new measurements of the relative abundances of the stable isotopes of silicon in terrestrial materials are presented. The total variation of delta/sup 30/Si found is 6.2 parts per thousand, centered on the mean of terrestrial mafic and ultramafic igneous rocks, delta/sup 30/Si = -0.4 parts per thousand. Igneous rocks show limited variation; coexisting minerals exhibit small, systematic silicon isotopic fractionations that are roughly 1/3 the magnitude of concomitant oxygen isotopic fractionations at 1150/sup 0/C. In both igneous minerals and rocks, delta/sup 30/Si shows a positive correlation with silicon content, as does delta/sup 18/O. Opal from both sponge spicules and sinters is light, with delta/sup 30/Si = -2.3 and -1.4 parts per thousand respectively. Large delta/sup 30/Si values of both positive and negative sign are reported for the first time from clay minerals, opaline phytoliths, and authigenic quartz. All highly fractionated samples were precipitated from solution at low temperatures; however, aqueous silicon is not measurably fractionated relative to quartz at equilibrium. A kinetic isotope fractionation of approximately 3.5 parts per thousand is postulated to occur during the low temperature precipitation of opal and, possibly, poorly ordered phyllosilicates, with the silicate phase being enriched in /sup 28/Si. This  More>>
Authors:
Douthitt, C B [1] 
  1. California Inst. of Tech., Pasadena (USA). Div. of Geological and Planetary Sciences
Publication Date:
Aug 01, 1982
Product Type:
Journal Article
Reference Number:
AIX-14-727585; EDB-83-052922
Resource Relation:
Journal Name: Geochim. Cosmochim. Acta; (United Kingdom); Journal Volume: 46:8
Subject:
58 GEOSCIENCES; IGNEOUS ROCKS; GEOCHEMISTRY; ISOTOPE RATIO; SILICON 30; ABUNDANCE; OXYGEN 18; SILICON 28; CHEMISTRY; EVEN-EVEN NUCLEI; ISOTOPES; LIGHT NUCLEI; NUCLEI; OXYGEN ISOTOPES; ROCKS; SILICON ISOTOPES; STABLE ISOTOPES; 580400* - Geochemistry- (-1989)
OSTI ID:
6762308
Country of Origin:
United Kingdom
Language:
English
Other Identifying Numbers:
Journal ID: CODEN: GCACA
Submitting Site:
HEDB
Size:
Pages: 1449-1458
Announcement Date:

Citation Formats

Douthitt, C B. Geochemistry of the stable isotopes of silicon. United Kingdom: N. p., 1982. Web. doi:10.1016/0016-7037(82)90278-2.
Douthitt, C B. Geochemistry of the stable isotopes of silicon. United Kingdom. doi:10.1016/0016-7037(82)90278-2.
Douthitt, C B. 1982. "Geochemistry of the stable isotopes of silicon." United Kingdom. doi:10.1016/0016-7037(82)90278-2. https://www.osti.gov/servlets/purl/10.1016/0016-7037(82)90278-2.
@misc{etde_6762308,
title = {Geochemistry of the stable isotopes of silicon}
author = {Douthitt, C B}
abstractNote = {One hundred thirty two new measurements of the relative abundances of the stable isotopes of silicon in terrestrial materials are presented. The total variation of delta/sup 30/Si found is 6.2 parts per thousand, centered on the mean of terrestrial mafic and ultramafic igneous rocks, delta/sup 30/Si = -0.4 parts per thousand. Igneous rocks show limited variation; coexisting minerals exhibit small, systematic silicon isotopic fractionations that are roughly 1/3 the magnitude of concomitant oxygen isotopic fractionations at 1150/sup 0/C. In both igneous minerals and rocks, delta/sup 30/Si shows a positive correlation with silicon content, as does delta/sup 18/O. Opal from both sponge spicules and sinters is light, with delta/sup 30/Si = -2.3 and -1.4 parts per thousand respectively. Large delta/sup 30/Si values of both positive and negative sign are reported for the first time from clay minerals, opaline phytoliths, and authigenic quartz. All highly fractionated samples were precipitated from solution at low temperatures; however, aqueous silicon is not measurably fractionated relative to quartz at equilibrium. A kinetic isotope fractionation of approximately 3.5 parts per thousand is postulated to occur during the low temperature precipitation of opal and, possibly, poorly ordered phyllosilicates, with the silicate phase being enriched in /sup 28/Si. This fractionation, coupled with a Rayleigh precipitation model, is capable of explaining most non-magmatic delta/sup 30/Si variations.}
doi = {10.1016/0016-7037(82)90278-2}
journal = {Geochim. Cosmochim. Acta; (United Kingdom)}
volume = {46:8}
journal type = {AC}
place = {United Kingdom}
year = {1982}
month = {Aug}
}