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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Rb-Sr ages from the Ocean of Storms

Rb-Sr internal isochron ages from Ocean of Storms, discussing analytical results of two texturally and mineralogically distinct crystalline rocks from Apollo 12

Papanastassiou, D. A.↗
NASA NTRS1971

Rb-Sr ages of igneous rocks from the Apollo 14 mission and the age of the Fra Mauro formation.

Internal Rb-Sr isochrons were determined on four basaltic rocks and on a basaltic clast from a breccia from the Fra Mauro landing site. An internal isochron was determined for rock 12004 and yielded a value in agreement with previous results for basaltic rocks from the Apollo 12 site. The crystallization ages for Apollo 14 basalts are only 0.2 to 0.3 AE older than were found for mare basalts from the Sea of Tranquility. Assuming these leucocratic igneous rocks to be representative of the Fra Mauro site, it follows that there were major igneous processes active in these regions, and presumably throughout the highlands, at times only slightly preceding the periods at which the maria were last flooded.

Papanastassiou, D. A.↗
NASA NTRS1972

Rb-Sr age of a Luna 16 basalt and the model age of lunar soils.

An internal isochron was determined on a small basalt fragment (sample B-1) returned from the Luna 16 mission, which yields an age of 3.42 plus or minus 0.8 b.y. and a low initial Sr87/Sr86 value. A comparison is made of the data from four lunar missions to mare sites which shows that the last period of major flooding of the mare basins is confined to a narrow time interval of only 0.55 b.y. The direct evidence of major lunar magmatic activity appears to be confined to the interval from 3.1 to 4.0 b.y. The Sr87/Sr86 values for all mare basalts are extremely primitive and lie in a rather narrow range. A diagram is given for initial Sr87/Sr86 as a function of time for all lunar rocks.

Papanastassiou, D. A.↗
NASA NTRS1972

The Rb-Sr age of a crystalline rock from Apollo 16.

Sample 68415 is one of the few large crystalline rocks returned from Apollo 16. A meaningful age may be obtained if the sample studied represents silicate material which was isotopically homogenized at the last time it was melted. It is also assumed that the constituent phases of the sample have remained closed systems subsequent to that time. The material was crushed and separated into different fractions with the aid of heavy liquids. It was found that the mineral separates are mixtures of at least three distinct phases with intrinsically different Rb/Sr ratios. An age of 3.84 aeon was determined.

Papanastassiou, D. A.↗
NASA NTRS1972

Rb-Sr systematics for chemically defined Apollo 14 breccias.

The Rb and Sr systematics were determined for eight lithic fragments from the coarse fines of Apollo 11, Apollo 12, and Apollo 14; for bulk soils from Luna 16, Apollo 14, and Apollo 15 and for 'whole rocks' from Apollo 14 and the Apollo 15 anorthosite 15415. The objective of the studies was to identify important lunar rock types by their major and trace element chemistry and utilize Rb and Sr systematics to obtain a chronology for events which establish or modify rock chemical composition.

Nyquist, L. E.↗
NASA NTRS1971

Uranium-bearing minerals of lunar rock 12013.

The U distribution in rock 12013 was studied by fission track and elemental mapping techniques. Major U-bearing phases are whitlockite, apatite, zircon, and phase beta, which is a Zr-Ti mineral rich in Fe, Nb, Y, REE, and containing up to 3.6% UO2, 4.7% ThO2 and 4.2% PbO. Calculated microprobe ages for phase beta average 4.0 b.y. and are in reasonable agreement with Rb-Sr and K-Ar ages. Phase beta plays a significant role in the U-Th-Pb systematics of rock 12012 and may play a similar role in the model ages of lunar soil.

Haines, E. L.↗