Sample 65795

65795 Highland Basalt 6.84 grams

Figure 1: Photo of 65795 with mm scale. S72-48955

Introduction

65795 is a rake sample from station 5 – see section on 65701. It has a basaltic texture, is highly aluminous and has high Ir and Au so it is considered an “impact melt”. 65795 has been dated at 3.81 b.y.

Petrography

Dowty et al. (1974), Warner et al. (1976) and Ryder and Norman (1980) describe 65795 as an igneous rock with “basaltic” texture (figure 2). Plagioclase laths are up to 1.5 mm long and poikilitically enclose pyroxene and olivine. Some plagioclase are blocky and may be relict xenocrysts. Plagioclsae is An98; olivine and pyroxene range in composition (figure 3). Accessory minerals are ilmenite, Ni-Fe metal, troilite and a silica phase.

Chemistry

Warner et al. (1976) reported major element analysis and Deutsch and Stoffler (1987) reported trace element analysis (table).

Radiogenic age dating

Deutsch and Stoffler (1987) determined a Rb-Sr isochron age of 3.81 b.y.for 65795 (figure ) with (ë87 = 1.42-11 yr-1).

Processing

There are 4 thin sections.

Figure 2: Photomicrograph of thin section 65795,2 Width of field is 2.5 mm.

Summary of Age Data for 65795

Rb-Sr

Deutsch and Stoffler 1987 $3.81 \pm 0.04 \text{ b.y}$

References for 65795

Butler P. (1972a) Lunar Sample Information Catalog Apollo 16. Lunar Receiving Laboratory. MSC 03210 Curator’s Catalog. pp. 370.

Deutsch A. and Stoffler D. (1987) Rb-Sr-analyses of Apollo 16 melt rocks and a new age estimate for the Imbrium basin: Lunar basin chronology and the early heavy bombardment of the moon. Geochim. Cosmochim. Acta 51, 1951-1964.

Dowty E., Keil K. and Prinz M. (1974a) Igneous rocks from Apollo 16 rake samples. Proc. 5^th Lunar Sci. Conf. 431-445.

Keil K., Dowty E., Prinz M. and Bunch T.E. (1972) Description, classification and inventory of 151 Apollo 16 rake samples from the LM area and station 5. Curator’s Catalog, JSC.

LSPET (1973b) The Apollo 16 lunar samples: Petrographic and chemical description. Science 179, 23-34.

LSPET (1972c) Preliminary examination of lunar samples. In Apollo 16 Preliminary Science Report. NASA SP-315, 7-1—7-58.

McKinley J.P., Taylor G.J., Keil K., Ma M.-S. and Schmitt R.A. (1984) Apollo 16: Impact sheets, contrasting nature of the Cayley Plains and Descartes Mountains, and geologic history. Proc. 14^th Lunar Planet. Sci. Conf. in J. Geophys. Res. 89, B513-B524.

Figure 3: Pyroxene and olivine in 65795 (Warner et al. 1976).

Figure 4: Internal Rb-Sr isochron for 65795 (Deutsch and Stofler 1984).

Ryder G. and Norman M.D. (1980) Catalog of Apollo 16 rocks (3 vol.). Curator’s Office pub. #52, JSC #16904

Sutton R.L. (1981) Documentation of Apollo 16 samples. In Geology of the Apollo 16 area, central lunar highlands. (Ulrich et al. ) U.S.G.S. Prof. Paper 1048.

Warner R.D., Dowty E., Prinz M., Conrad G.H., Nehru C.E. and Keil K. (1976c) Catalog of Apollo 16 rake samples from the LM area and station 5. Spec. Publ. #13, UNM Institute of Meteoritics, Albuquerque. 87 pp.

Lunar Sample Compendium C Meyer 2012

Table 1. Chemical composition of 65795

reference weight SiO2 % TiO2 Al2O3 FeO MnO	McKinely84 Dowty74	Deutsch87
MgO CaO Na2O K2O P2O5 S % sum		(a) 0.39 (a) 0.04	(b) (b)
Sc ppm		5.85	(b)
V Cr Co Ni Cu Zn Ga Ge ppb As Se Rb Sr Y Zr Nb Mo Ru Rh Pd ppb Ag ppb Cd ppb In ppb Sn ppb Sb ppb Te ppb Cs ppm Ba		450 25 360	(b) (b) (b)
La Ce		5.43 15.4	(b) (b)
Pr Nd Sm Eu Gd		8.6 2.52 1.01	(b) (b) (b)
Tb Dy Ho Er Tm Yb Lu Hf Ta W ppb Re ppb		0.57 3.81 0.79 2 0.3 1.82 0.25 1.91 0.26	(b) (b) (b) (b) (b) (b) (b) (b) (b)
Os ppb Ir ppb Pt ppb		12	(b)
Au ppb Th ppm U ppm	technique: (a) broad beam e probe, (b) INAA	3.8 0.84 0.25	(b) (b) (b)