EXPERIMENTALLY MELTING A MG#80 MARTIAN MANTLE AT 0.5 TO 2 GPA: IMPLICATIONS FOR BASALT GENESIS

EXPERIMENTALLY MELTING A MG#80 MARTIAN MANTLE AT 0.5 to 2 GPa: IMPLICATIONS FOR BASALT GENESIS

Author list: MCCOY, Christopher L⁽¹⁾, CHARTRAND, Zachary⁽¹⁾, CARPENTER, Paul⁽²⁾, GROSS, Juliane⁽³⁾, FILIBERTO, Justin⁽¹⁾

(1) Geology, Southern Illinois University, Carbondale, IL 62901 (2) Earth and Planetary Sciences, Washington University, 1 Brookings Drive, St Louis, MO 63130 (3) Earth and Planetary Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854

The Dreibus and Wanke [1] (DW) composition is the most widely accepted Martian mantle composition; however, recent work [2] has suggested that this composition may be too iron-rich to produce the Yamato 980459 bulk composition. Melting experiments using the DW composition produced with the Mg# of Y98 after 70% melting at 1 GPa [3]. To reduce the high degree of melting required by the Mg#75 composition, Musselwhite et al. [4] suggested multiple (2 to 3) partial melts or melting of a previously depleted source. Agee and Draper [2] suggested an increase in the Mg# of the Martian mantle (from 75 to 80) might instead produce Martian magmas at realistic percent partial melts. Therefore, we performed partial melting experiments from 0.5 to 2 GPa on a modified Martian mantle composition with an Mg#80. Our results produced a Y98-like magma composition 40-44% melt at 1 GPa and 1.5 GPa. This is 30% partial melting lower than using an Mg# 75 mantle composition (DW) and is more consistent with the amount of partial melting needed to produce Martian magmas (3- 27% for surface basalts; [5]). Further, our experimental results on an Mg#80 mantle successfully produce the range of Mg#s and bulk compositions of olivine shergottites (Mg#58 to Mg#66; [6]). Therefore, an Mg#80 composition mantle may be more realistic for the source region of the SNC meteorites.

[1] Dreibus, G., & Wanke, H. (1985) Meteoritics, 20, 367-381. [2] Agee, C. B., & Draper, D. S. (2004) EPSL, 224(3), 415-429. [3] Collinet, M. et al.(2015) EPSL, 427, 83-94. [4] Musselwhite, D. S., et al. (2006) MaPS, 41(9), 1271-1290. [5] Filiberto, J., & Dasgupta, R. (2015) JGR: Planets, 120(1), DOI:2014JE004745. [6] Filiberto, J., & Dasgupta, R. (2011) EPSL, 304(3), 527-537.