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Article: PGE distribution in 2.7-Ga layered komatiite flows from the Belingwe greenstone belt, Zimbabwe

TitlePGE distribution in 2.7-Ga layered komatiite flows from the Belingwe greenstone belt, Zimbabwe
Authors
Issue Date1994
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeo
Citation
Chemical Geology, 1994, v. 118 n. 1-4, p. 155-172 How to Cite?
AbstractThe well-preserved Anderson's and Onias's komatiite flows from the late Archaean Belingwe greenstone belt (∼ 2.7 Ga), Zimbabwe, were sampled in the SASKMAR drill hole. Anderson's Flow possesses a 1.1-m-thick B1 subzone and a clinopyroxene spinifex subzone, whereas Onias's Flow has spinifex and cumulate layers typical of komatiite flows. Platinum-group element (PGE) abundances throughout these two flows provide constraints on the formation of layered komatiite flows. All samples from both flows have similar chondrite-normalized PGE patterns that are enriched in Rh, Pt and Pd relative to Os and Ir, which are attributed to large degrees (>30%) of partial melting of the upper mantle. Their Pd/Ir ratios are highly variable (2.0-31 in Onias's Flow and 2.3-61 in Anderson's Flow). PGE variations within both flows, except the spinifex A zone and B1 subzone of Anderson's Flow, together with those of major and other trace elements, are consistent with a model involving olivine fractionation. The spinifex A zone of Anderson's Flow has low Pd/Ir ratios (6-8) which occur in an interval having negative Eu anomalies caused by hydrothermal alteration. The Pt fractionation from Pd and Rh is documented from their relationship to MgO contents: behaviours of Pd and Rh are similar and more incompatible than Pt at the early stage of relatively slow cooling but less incompatible at the late stage during the formation of komatiite flows. PGE in the B1 subzone of Anderson's Flow do not follow an olivine fractionation trend. Pd/Ir ratios in this subzone increase from 28 at the top to 61 at the base. These unusually high values can be accounted for by late-stage development of the subzone and strong fractionation. © 1994.
Persistent Identifierhttp://hdl.handle.net/10722/150965
ISSN
2015 Impact Factor: 3.482
2015 SCImago Journal Rankings: 2.346

 

DC FieldValueLanguage
dc.contributor.authorZhou, MFen_US
dc.date.accessioned2012-06-26T06:15:18Z-
dc.date.available2012-06-26T06:15:18Z-
dc.date.issued1994en_US
dc.identifier.citationChemical Geology, 1994, v. 118 n. 1-4, p. 155-172en_US
dc.identifier.issn0009-2541en_US
dc.identifier.urihttp://hdl.handle.net/10722/150965-
dc.description.abstractThe well-preserved Anderson's and Onias's komatiite flows from the late Archaean Belingwe greenstone belt (∼ 2.7 Ga), Zimbabwe, were sampled in the SASKMAR drill hole. Anderson's Flow possesses a 1.1-m-thick B1 subzone and a clinopyroxene spinifex subzone, whereas Onias's Flow has spinifex and cumulate layers typical of komatiite flows. Platinum-group element (PGE) abundances throughout these two flows provide constraints on the formation of layered komatiite flows. All samples from both flows have similar chondrite-normalized PGE patterns that are enriched in Rh, Pt and Pd relative to Os and Ir, which are attributed to large degrees (>30%) of partial melting of the upper mantle. Their Pd/Ir ratios are highly variable (2.0-31 in Onias's Flow and 2.3-61 in Anderson's Flow). PGE variations within both flows, except the spinifex A zone and B1 subzone of Anderson's Flow, together with those of major and other trace elements, are consistent with a model involving olivine fractionation. The spinifex A zone of Anderson's Flow has low Pd/Ir ratios (6-8) which occur in an interval having negative Eu anomalies caused by hydrothermal alteration. The Pt fractionation from Pd and Rh is documented from their relationship to MgO contents: behaviours of Pd and Rh are similar and more incompatible than Pt at the early stage of relatively slow cooling but less incompatible at the late stage during the formation of komatiite flows. PGE in the B1 subzone of Anderson's Flow do not follow an olivine fractionation trend. Pd/Ir ratios in this subzone increase from 28 at the top to 61 at the base. These unusually high values can be accounted for by late-stage development of the subzone and strong fractionation. © 1994.en_US
dc.languageengen_US
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/chemgeoen_US
dc.relation.ispartofChemical Geologyen_US
dc.titlePGE distribution in 2.7-Ga layered komatiite flows from the Belingwe greenstone belt, Zimbabween_US
dc.typeArticleen_US
dc.identifier.emailZhou, MF:mfzhou@hkucc.hku.hken_US
dc.identifier.authorityZhou, MF=rp00844en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-0028555106en_US
dc.identifier.volume118en_US
dc.identifier.issue1-4en_US
dc.identifier.spage155en_US
dc.identifier.epage172en_US
dc.publisher.placeNetherlandsen_US
dc.identifier.scopusauthoridZhou, MF=7403506005en_US

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