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In search of late-stage planetary building blocks

dc.contributor.authorWalker, Richard
dc.contributor.authorBermingham, Katherine
dc.contributor.authorLiu, Jingao
dc.contributor.authorPuchtel, Igor
dc.contributor.authorTouboul, Mathieu
dc.description.abstractGenetic contributions to the final stages of planetary growth, including materials associated with the giant Moon forming impact, late accretion, and late heavy bombardment are examined using siderophile elements. Isotopic similarities between the Earth and Moon for both lithophile and siderophile elements collectively lead to the suggestion that the genetics of the building blocks for Earth, and the impactor involved in the Moon-forming event were broadly similar, and shared some strong genetic affinities with enstatite chondrites. The bulk genetic fingerprint of materials subsequently added to Earth by late accretion, defined as the addition of ~0.5 wt.% of Earth's mass to the mantle, following cessation of core formation, was characterized by 187Os/188Os and Pd/Ir ratios that were also similar to those in some enstatite chondrites. However, the integrated fingerprint of late accreted matter differs from enstatite chondrites in terms of the relative abundances of certain other HSE, most notably Ru/Ir. The final ≤0.05 wt.% addition of material to the Earth and Moon, believed by some to be part of a late heavy bombardment, included a component with much more fractionated relative HSE abundances than evidenced in the average late accretionary component. Heterogeneous 182W/184Wisotopic compositions of some ancient terrestrial rocks suggest that some very early formed mantle domains remained chemically distinct for long periods of time following primary planetary accretion. This evidence for sluggish mixing of the early mantle suggests that if late accretionary contributions to the mantle were genetically diverse, it may be possible to isotopically identify the disparate primordial components in the terrestrial rock record using the siderophile element tracers Ru and Mo.en_US
dc.description.sponsorshipNASA grants NNX13AF83G and NNA14AB07A NSF-CSEDI grants EAR1160728 and EAR1265169.en_US
dc.publisherElsevier - Chemical Geologyen_US
dc.subjectBuilding blocks, Giant impact, Late accretion, Late heavy bombardment, Siderophile elementsen_US
dc.titleIn search of late-stage planetary building blocksen_US
dc.relation.isAvailableAtCollege of Computer, Mathematical & Natural Sciencesen_us
dc.relation.isAvailableAtDigital Repository at the University of Marylanden_us
dc.relation.isAvailableAtUniversity of Maryland (College Park, MD)en_us

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