Petrogenetic association of the oldest lunar basalts: Combined Rb-Sr isotopic and trace element constraints

作者：Hui Hejiu^*; Neal Clive R; Shih Chi Yu; Nyquist Laurence E

来源：Earth and Planetary Science Letters, 2013, 373: 150-159.

DOI：10.1016/j.epsl.2013.04.034

• Apollo 14
• high-Al basalt
• Rb-Sr isotopic system
• radiometric age
• incompatible trace element
• mixing

We report a new radiometric Rb-Sr age determination of 4.03 +/- 0.04 Ga for high-Al basaltic clast 14321,1353, which is a Group B Apollo 14 high-Al basalt based on its whole-rock incompatible-trace-element chemistry. In addition, available literature Rb-Sr isotope data for Apollo 14 high-Al basalts were reprocessed using the same decay constant and data reduction protocol as used for sample 14321,1353. The Rb-Sr isotopic ages of high-Al basalts range from 431 +/- 0.17 to 3.93 +/- 0.06 Ga. The trace element and Rb-Sr isotopic compositions of high-Al basalts are distinct from those of Apollo 14 aluminous impact melts that crystallized at 3.86 +/- 0.01 Ga. The Rb-Sr isotope systematics, coupled with incompatible-trace-element data are consistent with the parental melts of Apollo 14 high-Al basalts being derived from sources consisting of primitive crystallization products of the lunar magma ocean that were variably metasomatized by late-stage KREEP-rich fluids. Our new Rb-Sr isotopic age for 14321,1353 suggests that the KREEP metasomatism must occur in the lunar mantle no later than 4.03 +/- 0.04 Ga. Collectively, the Apollo 14 high-Al basalts represent the earliest known volcanic products from the Moon and place a time constraint on the formation of the high-Al basalt source through the crystallization of the lunar magma ocean.

• 出版日期2013-7-1