Source of potassium in shocked ordinary chondrites

J. R. Weirich, T. D. Swindle, C. E. Isachsen, Thomas Sharp, C. Li, R. T. Downs

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Argon-argon dating (a variation of potassium-argon dating) of ordinary chondrites is being used to reconstruct the collisional impact history of their parent bodies. However, due to the fine-grained, multi-mineral, highly shocked nature of chondrites, the sources of potassium (K) in these meteorites have not been fully identified. By locating and isolating the different sources prior to analysis, better ages can be obtained. To distinguish between possible sources, we have analyzed Chico and Northwest Africa 091 (both L6 chondrites) via K mass balance, Raman spectroscopy, and argon (Ar) diffusion studies.In accordance with previous studies on other ordinary chondrites, the Ar in these two chondrites is nearly equally split between two releases, and the lower temperature release is identified as sodium-rich feldspar. Various scenarios for the higher temperature release are investigated, but no scenario meets all the required criteria. The Ar activation energy of the higher temperature release is the same as pyroxene, but the pyroxene has no detectable K. The K mass balance shows feldspar can account for all the K in the chondrite; hence feldspar must be the ultimate source of the higher temperature release. Raman spectroscopy rules out a high-pressure phase of feldspar. Neither melt veins, nor feldspar inclusions in pyroxene, are abundant enough to account for the higher temperature release in these meteorites.

Original languageEnglish (US)
Pages (from-to)125-139
Number of pages15
JournalGeochimica et Cosmochimica Acta
Volume98
DOIs
StatePublished - Dec 1 2012

Fingerprint

ordinary chondrite
Argon
feldspar
Potassium
potassium
chondrite
argon
pyroxene
Meteorites
Raman spectroscopy
argon-argon dating
meteorite
mass balance
potassium-argon dating
Temperature
parent body
activation energy
Minerals
sodium
melt

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Weirich, J. R., Swindle, T. D., Isachsen, C. E., Sharp, T., Li, C., & Downs, R. T. (2012). Source of potassium in shocked ordinary chondrites. Geochimica et Cosmochimica Acta, 98, 125-139. https://doi.org/10.1016/j.gca.2012.09.006

Source of potassium in shocked ordinary chondrites. / Weirich, J. R.; Swindle, T. D.; Isachsen, C. E.; Sharp, Thomas; Li, C.; Downs, R. T.

In: Geochimica et Cosmochimica Acta, Vol. 98, 01.12.2012, p. 125-139.

Research output: Contribution to journalArticle

Weirich, JR, Swindle, TD, Isachsen, CE, Sharp, T, Li, C & Downs, RT 2012, 'Source of potassium in shocked ordinary chondrites', Geochimica et Cosmochimica Acta, vol. 98, pp. 125-139. https://doi.org/10.1016/j.gca.2012.09.006
Weirich, J. R. ; Swindle, T. D. ; Isachsen, C. E. ; Sharp, Thomas ; Li, C. ; Downs, R. T. / Source of potassium in shocked ordinary chondrites. In: Geochimica et Cosmochimica Acta. 2012 ; Vol. 98. pp. 125-139.
@article{c0d1448617ad4ec29e3726a762ff05a1,
title = "Source of potassium in shocked ordinary chondrites",
abstract = "Argon-argon dating (a variation of potassium-argon dating) of ordinary chondrites is being used to reconstruct the collisional impact history of their parent bodies. However, due to the fine-grained, multi-mineral, highly shocked nature of chondrites, the sources of potassium (K) in these meteorites have not been fully identified. By locating and isolating the different sources prior to analysis, better ages can be obtained. To distinguish between possible sources, we have analyzed Chico and Northwest Africa 091 (both L6 chondrites) via K mass balance, Raman spectroscopy, and argon (Ar) diffusion studies.In accordance with previous studies on other ordinary chondrites, the Ar in these two chondrites is nearly equally split between two releases, and the lower temperature release is identified as sodium-rich feldspar. Various scenarios for the higher temperature release are investigated, but no scenario meets all the required criteria. The Ar activation energy of the higher temperature release is the same as pyroxene, but the pyroxene has no detectable K. The K mass balance shows feldspar can account for all the K in the chondrite; hence feldspar must be the ultimate source of the higher temperature release. Raman spectroscopy rules out a high-pressure phase of feldspar. Neither melt veins, nor feldspar inclusions in pyroxene, are abundant enough to account for the higher temperature release in these meteorites.",
author = "Weirich, {J. R.} and Swindle, {T. D.} and Isachsen, {C. E.} and Thomas Sharp and C. Li and Downs, {R. T.}",
year = "2012",
month = "12",
day = "1",
doi = "10.1016/j.gca.2012.09.006",
language = "English (US)",
volume = "98",
pages = "125--139",
journal = "Geochmica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Source of potassium in shocked ordinary chondrites

AU - Weirich, J. R.

AU - Swindle, T. D.

AU - Isachsen, C. E.

AU - Sharp, Thomas

AU - Li, C.

AU - Downs, R. T.

PY - 2012/12/1

Y1 - 2012/12/1

N2 - Argon-argon dating (a variation of potassium-argon dating) of ordinary chondrites is being used to reconstruct the collisional impact history of their parent bodies. However, due to the fine-grained, multi-mineral, highly shocked nature of chondrites, the sources of potassium (K) in these meteorites have not been fully identified. By locating and isolating the different sources prior to analysis, better ages can be obtained. To distinguish between possible sources, we have analyzed Chico and Northwest Africa 091 (both L6 chondrites) via K mass balance, Raman spectroscopy, and argon (Ar) diffusion studies.In accordance with previous studies on other ordinary chondrites, the Ar in these two chondrites is nearly equally split between two releases, and the lower temperature release is identified as sodium-rich feldspar. Various scenarios for the higher temperature release are investigated, but no scenario meets all the required criteria. The Ar activation energy of the higher temperature release is the same as pyroxene, but the pyroxene has no detectable K. The K mass balance shows feldspar can account for all the K in the chondrite; hence feldspar must be the ultimate source of the higher temperature release. Raman spectroscopy rules out a high-pressure phase of feldspar. Neither melt veins, nor feldspar inclusions in pyroxene, are abundant enough to account for the higher temperature release in these meteorites.

AB - Argon-argon dating (a variation of potassium-argon dating) of ordinary chondrites is being used to reconstruct the collisional impact history of their parent bodies. However, due to the fine-grained, multi-mineral, highly shocked nature of chondrites, the sources of potassium (K) in these meteorites have not been fully identified. By locating and isolating the different sources prior to analysis, better ages can be obtained. To distinguish between possible sources, we have analyzed Chico and Northwest Africa 091 (both L6 chondrites) via K mass balance, Raman spectroscopy, and argon (Ar) diffusion studies.In accordance with previous studies on other ordinary chondrites, the Ar in these two chondrites is nearly equally split between two releases, and the lower temperature release is identified as sodium-rich feldspar. Various scenarios for the higher temperature release are investigated, but no scenario meets all the required criteria. The Ar activation energy of the higher temperature release is the same as pyroxene, but the pyroxene has no detectable K. The K mass balance shows feldspar can account for all the K in the chondrite; hence feldspar must be the ultimate source of the higher temperature release. Raman spectroscopy rules out a high-pressure phase of feldspar. Neither melt veins, nor feldspar inclusions in pyroxene, are abundant enough to account for the higher temperature release in these meteorites.

UR - http://www.scopus.com/inward/record.url?scp=84867744785&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84867744785&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2012.09.006

DO - 10.1016/j.gca.2012.09.006

M3 - Article

AN - SCOPUS:84867744785

VL - 98

SP - 125

EP - 139

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

ER -