DOI: 10.1016/j.epsl.2018.04.040
Scopus记录号: 2-s2.0-85047077007
论文题名: Chondritic late accretion to Mars and the nature of shergottite reservoirs
作者: Tait K.T. ; Day J.M.D.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 494 起始页码: 99
结束页码: 108
语种: 英语
英文关键词: highly siderophile elements
; isotopic evolution
; late accretion
; mantle
; Mars
; shergottites
Scopus关键词: Earth (planet)
; Filtration
; Igneous rocks
; Isotopes
; Magnesia
; Meteorites
; Moon
; Palladium
; Platinum
; Regression analysis
; Silicates
; Sulfur compounds
; Trace elements
; Highly siderophile elements
; isotopic evolution
; Late accretions
; mantle
; Mars
; shergottites
; Ruthenium
英文摘要: Mars is considered to have formed as a planetary embryo that experienced extensive differentiation early in its history. Shergottite meteorites preserve evidence for this history, and for late accretion events that affected their mantle sources within Mars. Here we report the first coupled 187Re–187Os, 87Sr/86Sr, highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) and major element abundance dataset for martian shergottites that span a range of MgO contents, from 6.4 to 30.3 wt.%. The shergottites range from picro-basalt to basaltic-andesite compositions, have enriched to depleted incompatible trace-element compositions, and define fractional crystallization trends, enabling the determination of HSE compatibility for martian magmatism in the order: Os > Ir ≥ Ru ≫ Pt ≥ Pd ≥ Re. This order of compatibility is like that defined previously for Earth and the Moon, but the fractionation of strongly compatible Os, Ir and Ru appears to take place at higher MgO contents in martian magmas, due to early onset of sulfide fractionation. In general, enriched shergottites have lower MgO contents than intermediate or depleted shergottites and have fractionated HSE patterns (Re + Pd + Pt > Ru + Ir + Os) and more radiogenic measured 87Sr/86Sr (0.7127–0.7235) and 187Os/188Os (0.140–0.247) than intermediate or depleted shergottite meteorites (87Sr/86Sr = 0.7010–0.7132; 187Os/188Os = 0.127–0.141). Osmium isotope compositions, corrected for crystallization age, define compositions that are implausibly unradiogenic in some enriched shergottites, implying recent mobilization of Re in some samples. Filtering for the effects of alteration and high Re/Os through crystal-liquid fractionation leads to a positive correlation between age-corrected Sr and Os isotope compositions. Mixing between hypothetical martian crustal and mantle reservoirs are unable to generate the observed Sr–Os isotope compositions of shergottites, which require either distinct and discrete long-term incompatible-element depleted and enriched mantle sources, or originate from hybridized melting of deep melts with metasomatized martian lithosphere. Using MgO-regression methods, we obtain a modified estimate of the bulk silicate Mars HSE composition of (in ng g−1) 0.4 [Re], 7.4 [Pd], 9.6 [Pt], 6.2 [Ru], 3.7 [Ir], 4 [Os], and a long-term chondritic 187Os/188Os ratio (∼0.1312). This result does not permit existing models invoking high-pressure and temperature partitioning of the HSE. Instead, our estimate implies 0.6–0.7% by mass of late accretion of broadly chondritic material to Mars. Our results indicate that Mars could have accreted earlier than Earth, but that disproportional accretion of large bodies and a relative constant flux of accretion of available materials in the first 50–100 Ma of Solar System led to the broad similarity in HSE abundances between Earth and Mars. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109844
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Royal Ontario Museum, 100 Queens Park, Toronto, ON M5S 2C6, Canada; Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0244, United States
Recommended Citation:
Tait K.T.,Day J.M.D.. Chondritic late accretion to Mars and the nature of shergottite reservoirs[J]. Earth and Planetary Science Letters,2018-01-01,494