Sample 68519

68519

Glass-coated Impact Melt Breccia 10.56 grams

Figure 1: Photo of 68519. Scale in cm/mm. S72-49569

Introduction

68519 is a rake sample collected from station 8 soil in an area thought of have disturbance from South Ray Crater – see section on 68501. This small lithic fragment had a glass coat that has been partially chipped away by micrometeorite bombardment.

Petrography

Ryder and Norman (1980) described 68519 as a “clastrich impact melt”. The matrix consists of about 75% plagioclase laths, less that 150 microns, with interstitial mafic minerals. Opaque phases are small and not welldeveloped and include armalcolite, Fe-metal and troilite. Hunter and Taylor (1981) looked for rust. Numerous inclusions of plagioclase indicate that the protolith was a breccia (figure 2).

Compositional variation of Apollo 16 impact-melt rocks is discussed by Korotev (1994).

Chemistry

68519 appears to have a high Mg/Fe ratio.

Radiogenic age dating

Norman et al. (2006) attempted to data 68519, but found that there was no Ar plateau. Age may be about 3.9 b.y., but who knows?

Processing

There are 2 thin sections.

Figure 3: Ar/Ar pleateau diagram for 68519 (Norman et al. 2006).

References for 68519

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

Hunter R.H. and Taylor L.A. (1981) Rust and schreibersite in Apollo 16 highland rocks: Manifestations of volatileelement mobility. Proc. 12th Lunar Planet. Sci. Conf. 253- 259.

Korotev R.L. (1994) Compositional variation in Apollo 16 impact melt breccias and inferences for the geology and bombardment history of the central highlands of the Moon. Geochim. Cosmochim. Acta 58, 3931-3969.

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.

Norman M.D., Duncan R.A. and Huard J.J. (2006) Identifying impact events within the lunar cataclysm from 40Ar-39Ar ages and compositions of Apollo 16 impact melt rocks. Geochim. Cosmochim. Acta 70, 6032-6049.

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

Ryder G. and Seymour R. (1982) Chemistry of Apollo 16 impact melts: Numerous melt sheets, lunar cratering history and the Cayley-Descartes distinction (abs). Lunar Planet. Sci. XIII, 673-674. Lunar Institute in Houston.

See T.H., Horz F. and Morris R.V. (1986) Apollo 16 impactmelt splashes: Petrography and major-element composition. Proc. 17th Lunar Planet. Sci. Conf. in J. Geophys. Res. 91, E3-E20.

Smith J.V. and Steele I.M. (1972c) Apollo 16 rake samples 67515 to 68537: Sample classification, description and inventory. Curator Catalog, JSC

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.

Table 1. Chemical composition of 68519.

reference weight SiO2 % TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 S % sum	glass Morris86		Ryder82		anor See87
	45.65 0.44	(a)	(b) 46		(a) 45.2 0.05	(b) (b)
	26 4.87	(a) 5	(a) 23.5		(a) 30.82 (a) 1.93 0.03 (a) 4.78 (a) 16.61 (a) 0.6 (a) 0.05	(b) (b) (b) (b) (b) (b) (b)
	7.77 14.55 0.51 0.14		(b) 9.3 (a) 14.6 (a) 0.47 (a) 0.19
Sc ppm V	5.61		(a) 7.1	(b)
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 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W ppb Re ppb Os ppb Ir ppb Pt ppb Au ppb Th ppm U ppm technique: (a) fused bead e. prob and INAA	749 35 553	(a) (a)	(a) 39	(b)
	144 13.22 46.5	(a) (a)	(a) 16.9	(b)
	6.21 1.13		(a) 7.8 (a) 1.2	(b) (b)
	1.14	(a)
	3.96 0.51 4.28 0.61	(a) (a) (a)	(a) 0.81	(b)
	2.34 0.86	(a) (a)