A new mineral with an olivine structure and pyroxene composition in the shock-induced melt veins of Tenham L6 chondrite

Zhidong Xie, Thomas Sharp, Kurt Leinenweber, Paul S. DeCarli, Przemek Dera

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We report a new mineral that occurs in shock-induced melt veins of the Tenham L6 chondrite. The new mineral, identified by transmission electron microscopy (TEM), occurs as acicular nanocrystals in a glassy matrix at the edge of shock-induced melt veins that crystallized during rapid quench at high pressure. The elongate crystals have aspect ratios up to 25. Widths range from ∼5 to ∼40 nm and lengths are up to 500 nm. Energy-dispersive X-ray spectroscopy (EDS) analyses provide the relative cation abundances that are consistent with a pyroxene-like stoichiometry: Na0.06Ca 0.02Mg0.71Fe0.20Al0.11 Si 0.94O3. Selected area electron diffraction (SAED) patterns from single-crystal and polycrystalline aggregates indicate an olivine structure with refined cell parameters: a = 4.78, b = 10.11, and c = 5.94 Å and a calculated density of 3.32 g/cm3. Synchrotron X-ray microdiffraction data are consistent with an olivine structure and provide similar cell parameters: a = 4.778, b = 10.267, c = 5.937 A. The pyroxene composition represents a large deviation from olivine stoichiometry, (Na 0.08Ca0.03Mg0.95 Fe0.26Al 0.15Si0.250.28)2Si 1O4, with 0.28 formula units of vacancies (□), 0.11 of Na+ plus Ca2+, and 0.25 of Si4+, in octahedral sites. Our observations indicate that a metastable and nonstoichiometric olivine structure can crystallize from a silicate melt during rapid quench. Trace amounts of such defects may be present in stable olivines in the deep upper mantle.

Original languageEnglish (US)
Pages (from-to)430-436
Number of pages7
JournalAmerican Mineralogist
Volume96
Issue number2-3
DOIs
StatePublished - Feb 2011

Fingerprint

chondrites
new mineral
veins
chondrite
olivine
pyroxene
Minerals
shock
minerals
melt
Chemical analysis
stoichiometry
Stoichiometry
crystal
Silicates
silicate melt
cells
Synchrotrons
Electron diffraction
Nanocrystals

Keywords

  • Melt vein
  • Olivine
  • Shock-induced
  • Tenham

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

A new mineral with an olivine structure and pyroxene composition in the shock-induced melt veins of Tenham L6 chondrite. / Xie, Zhidong; Sharp, Thomas; Leinenweber, Kurt; DeCarli, Paul S.; Dera, Przemek.

In: American Mineralogist, Vol. 96, No. 2-3, 02.2011, p. 430-436.

Research output: Contribution to journalArticle

@article{3c043869a5504e29908569a4e120f111,
title = "A new mineral with an olivine structure and pyroxene composition in the shock-induced melt veins of Tenham L6 chondrite",
abstract = "We report a new mineral that occurs in shock-induced melt veins of the Tenham L6 chondrite. The new mineral, identified by transmission electron microscopy (TEM), occurs as acicular nanocrystals in a glassy matrix at the edge of shock-induced melt veins that crystallized during rapid quench at high pressure. The elongate crystals have aspect ratios up to 25. Widths range from ∼5 to ∼40 nm and lengths are up to 500 nm. Energy-dispersive X-ray spectroscopy (EDS) analyses provide the relative cation abundances that are consistent with a pyroxene-like stoichiometry: Na0.06Ca 0.02Mg0.71Fe0.20Al0.11 Si 0.94O3. Selected area electron diffraction (SAED) patterns from single-crystal and polycrystalline aggregates indicate an olivine structure with refined cell parameters: a = 4.78, b = 10.11, and c = 5.94 {\AA} and a calculated density of 3.32 g/cm3. Synchrotron X-ray microdiffraction data are consistent with an olivine structure and provide similar cell parameters: a = 4.778, b = 10.267, c = 5.937 A. The pyroxene composition represents a large deviation from olivine stoichiometry, (Na 0.08Ca0.03Mg0.95 Fe0.26Al 0.15Si0.25□0.28)2Si 1O4, with 0.28 formula units of vacancies (□), 0.11 of Na+ plus Ca2+, and 0.25 of Si4+, in octahedral sites. Our observations indicate that a metastable and nonstoichiometric olivine structure can crystallize from a silicate melt during rapid quench. Trace amounts of such defects may be present in stable olivines in the deep upper mantle.",
keywords = "Melt vein, Olivine, Shock-induced, Tenham",
author = "Zhidong Xie and Thomas Sharp and Kurt Leinenweber and DeCarli, {Paul S.} and Przemek Dera",
year = "2011",
month = "2",
doi = "10.2138/am.2011.3437",
language = "English (US)",
volume = "96",
pages = "430--436",
journal = "American Mineralogist",
issn = "0003-004X",
publisher = "Mineralogical Society of America",
number = "2-3",

}

TY - JOUR

T1 - A new mineral with an olivine structure and pyroxene composition in the shock-induced melt veins of Tenham L6 chondrite

AU - Xie, Zhidong

AU - Sharp, Thomas

AU - Leinenweber, Kurt

AU - DeCarli, Paul S.

AU - Dera, Przemek

PY - 2011/2

Y1 - 2011/2

N2 - We report a new mineral that occurs in shock-induced melt veins of the Tenham L6 chondrite. The new mineral, identified by transmission electron microscopy (TEM), occurs as acicular nanocrystals in a glassy matrix at the edge of shock-induced melt veins that crystallized during rapid quench at high pressure. The elongate crystals have aspect ratios up to 25. Widths range from ∼5 to ∼40 nm and lengths are up to 500 nm. Energy-dispersive X-ray spectroscopy (EDS) analyses provide the relative cation abundances that are consistent with a pyroxene-like stoichiometry: Na0.06Ca 0.02Mg0.71Fe0.20Al0.11 Si 0.94O3. Selected area electron diffraction (SAED) patterns from single-crystal and polycrystalline aggregates indicate an olivine structure with refined cell parameters: a = 4.78, b = 10.11, and c = 5.94 Å and a calculated density of 3.32 g/cm3. Synchrotron X-ray microdiffraction data are consistent with an olivine structure and provide similar cell parameters: a = 4.778, b = 10.267, c = 5.937 A. The pyroxene composition represents a large deviation from olivine stoichiometry, (Na 0.08Ca0.03Mg0.95 Fe0.26Al 0.15Si0.25□0.28)2Si 1O4, with 0.28 formula units of vacancies (□), 0.11 of Na+ plus Ca2+, and 0.25 of Si4+, in octahedral sites. Our observations indicate that a metastable and nonstoichiometric olivine structure can crystallize from a silicate melt during rapid quench. Trace amounts of such defects may be present in stable olivines in the deep upper mantle.

AB - We report a new mineral that occurs in shock-induced melt veins of the Tenham L6 chondrite. The new mineral, identified by transmission electron microscopy (TEM), occurs as acicular nanocrystals in a glassy matrix at the edge of shock-induced melt veins that crystallized during rapid quench at high pressure. The elongate crystals have aspect ratios up to 25. Widths range from ∼5 to ∼40 nm and lengths are up to 500 nm. Energy-dispersive X-ray spectroscopy (EDS) analyses provide the relative cation abundances that are consistent with a pyroxene-like stoichiometry: Na0.06Ca 0.02Mg0.71Fe0.20Al0.11 Si 0.94O3. Selected area electron diffraction (SAED) patterns from single-crystal and polycrystalline aggregates indicate an olivine structure with refined cell parameters: a = 4.78, b = 10.11, and c = 5.94 Å and a calculated density of 3.32 g/cm3. Synchrotron X-ray microdiffraction data are consistent with an olivine structure and provide similar cell parameters: a = 4.778, b = 10.267, c = 5.937 A. The pyroxene composition represents a large deviation from olivine stoichiometry, (Na 0.08Ca0.03Mg0.95 Fe0.26Al 0.15Si0.25□0.28)2Si 1O4, with 0.28 formula units of vacancies (□), 0.11 of Na+ plus Ca2+, and 0.25 of Si4+, in octahedral sites. Our observations indicate that a metastable and nonstoichiometric olivine structure can crystallize from a silicate melt during rapid quench. Trace amounts of such defects may be present in stable olivines in the deep upper mantle.

KW - Melt vein

KW - Olivine

KW - Shock-induced

KW - Tenham

UR - http://www.scopus.com/inward/record.url?scp=79952165937&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79952165937&partnerID=8YFLogxK

U2 - 10.2138/am.2011.3437

DO - 10.2138/am.2011.3437

M3 - Article

AN - SCOPUS:79952165937

VL - 96

SP - 430

EP - 436

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 2-3

ER -