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Mixing relations of the howardite‐eucrite‐diogenite suite: A new statistical approach of independent component analysis for the Dawn mission
Author(s) -
Usui Tomohiro,
Iwamori Hikaru
Publication year - 2013
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12205
Subject(s) - meteorite , parent body , geology , olivine , geochemistry , asteroid , astrobiology , physics , chondrite
Dawn has recently revealed that the surface of Vesta is heterogeneously covered by polymictic regoliths represented by mixtures of howardite, eucrite, and diogenite ( HED ) meteorites. Mixing relations of the HED suite are examined here using a new computational statistical approach of independent component analysis ( ICA ). We performed eight‐component ICA (Si, Ti, Al, Cr, Fe, Mn, Mg, and Ca) for 209 HED bulk‐rock compositions. The ICA results indicate that the HED bulk‐rock compositions can be reduced into three independent components ( IC ) and these IC vectors can reasonably explain compositional variation, petrographic observations, and the mixing relations of the HED suite. The IC ‐1 vector represents a eucrite variation that extends from cumulate eucrite toward main‐group ( MG ) and incompatible‐element enriched eucrites. The IC ‐2 vector represents a compositional variation of howardites that extends from diogenites to MG ‐eucrites, indicating the well‐known two‐component mixing trend of diogenite and eucrite. The IC ‐3 vector represents a compositional variation defined by diogenites and olivine‐bearing diogenites, suggesting mixing of olivine and orthopyroxene. Among the three IC s, the diogenite‐eucrite mixing trend IC ‐2 is most statistically robust and dominates the compositional variations of the HED suite. Our ICA study further indicates that the combination of only three elements (Mg, Si, and Fe) approximates the eight‐component ICA model, and that the limited number of resolvable γ‐ray spectra obtained by the Dawn mission possibly discriminates olivine lithologies from the olivine‐free regolith breccias on the surface of Vesta.