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dc.contributor.authorRasmussen, Birger
dc.contributor.authorFletcher, Ian
dc.contributor.authorGregory, Courtney
dc.contributor.authorMuhling, Janet
dc.contributor.authorSuvorova, Alexandra
dc.date.accessioned2017-01-30T15:14:47Z
dc.date.available2017-01-30T15:14:47Z
dc.date.created2013-03-10T20:00:28Z
dc.date.issued2012
dc.identifier.citationRasmussen, Birger and Fletcher, Ian and Gregory, Courtney and Muhling, Janet and Suvorova, Alexandra. 2012. Tranquillityite: The last lunar mineral comes down to Earth. Geology 40 (1): pp. 83-86.
dc.identifier.urihttp://hdl.handle.net/20.500.11937/44543
dc.identifier.doi10.1130/G32525.1
dc.description.abstract

Tranquillityite [Fe2+8(ZrY)2Ti3Si3O24] was first discovered in mare basalts collected during the Apollo 11 lunar mission to the Sea of Tranquillity. The mineral has since been found exclusively in returned lunar samples and lunar meteorites, with no terrestrial counterpart. We have now identified tranquillityite in six dolerite dikes and sills from Western Australia. Terrestrial tranquillityite commonly occurs as clusters of fox-red laths closely associated with baddeleyite and zirconolite in quartz and K-feldspar intergrowths in late-stage interstices between plagioclase and pyroxene. Its composition is relatively uniform, comprising mostly Si, Zr, Ti, and Fe, with minor Al, Mg, Mn, Ca, Nb, Hf, Y, and rare earth elements. Its habit and chemistry are consistent with tranquillityite in lunar basalts, and it has a face-centered-cubic subcell, similar to that of annealed lunar tranquillityite. Unlike coexisting baddeleyite and zirconolite, it is commonly altered to a secondary intergrowth of submicron phases comprising mainly Si, Ti, and Ca, with minor Zr. In situ sensitive high-resolution ion microprobe (SHRIMP) U-Pb geochronology of tranquillityite from sills intruding the Eel Creek Formation, northeastern Pilbara Craton, yields a 207Pb/206Pb age of 1064 ± 14 Ma. This age indicates that the previously undated sills belong to the ca. 1070 Ma Warakurna large igneous province, extending the geographic range of this mafic complex. The date also provides a new minimum age (>1.05 Ga) for the intruded sedimentary rocks, which were previously thought to be Neoproterozoic. Examination of dolerite from Western Australia suggests that tranquillityite is a relatively widespread, albeit volumetrically minor, accessory mineral and, where sufficiently coarse, it represents an exceptional new U-Pb geochronometer.

dc.publisherGeological Society of America
dc.subjectTranquillityite
dc.subjectApollo 11
dc.subjectU-Pb geochronometer
dc.subjectEel Creek Formation
dc.titleTranquillityite: The last lunar mineral comes down to Earth
dc.typeJournal Article
dcterms.source.volume40
dcterms.source.number1
dcterms.source.startPage83
dcterms.source.endPage86
dcterms.source.issn0091-7613
dcterms.source.titleGeology
curtin.department
curtin.accessStatusFulltext not available


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