CaltechAUTHORS
  A Caltech Library Service

Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona

McCanta, M. C. and Beckett, J. R. and Stolper, E. M. (2016) Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona. Meteoritics and Planetary Science, 51 (3). pp. 520-546. ISSN 1086-9379. http://resolver.caltech.edu/CaltechAUTHORS:20160222-080945532

[img] PDF - Published Version
See Usage Policy.

3103Kb
[img] PDF (Data S1. Summaries of petrographic and compositional observations) - Supplemental Material
See Usage Policy.

46Kb

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20160222-080945532

Abstract

Phosphorus zoning is observed in olivines in high-FeO (type IIA) chondrules in H chondrites over the entire range of petrologic grades: H3.1–H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in olivines that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in chondrule olivines. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in olivine is roughly 1:1 (3:1 for one zone in one olivine in RC 075), consistent with Cr^(3+) charge-balancing P^(5+) substituting for Si^(4+). Normal igneous zonation involving the dominant chrome species Cr^(2+) was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5–H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4–H6 chondrites, P-correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix olivines that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the chondrule–matrix interface suggests that this is a response to metasomatic processes. We also observed P-enriched halos near the chondrule–matrix interface in H3.3–H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the chondrule surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. Olivines in type IA chondrules show none of the P-zoning ubiquitous in type IIA chondrules or terrestrial igneous olivines, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA chondrules.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1111/maps.12604DOIArticle
http://onlinelibrary.wiley.com/doi/10.1111/maps.12604/abstractPublisherArticle
http://onlinelibrary.wiley.com/doi/10.1111/maps.12604/suppinfoPublisherSupporting Information
ORCID:
AuthorORCID
Stolper, E. M.0000-0001-8008-8804
Additional Information:© 2016 The Meteoritical Society. Received 22 September 2014; revision accepted 16 November 2015. Article first published online: 18 Feb. 2016. The authors are grateful to Ma Chi for electron microprobe assistance. The reviews of J. S. Boesenberg, R. H. Jones, and S. C. Kohn were thorough and greatly appreciated. This work was supported by NASA grant NNX12AH63G.
Funders:
Funding AgencyGrant Number
NASANNX12AH63G
Record Number:CaltechAUTHORS:20160222-080945532
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160222-080945532
Official Citation:McCanta, M. C., Beckett, J. R. and Stolper, E. M. (2016), Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona. Meteoritics & Planetary Science, 51: 520–546. doi: 10.1111/maps.12604
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64620
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Feb 2016 18:15
Last Modified:15 Apr 2016 20:17

Repository Staff Only: item control page