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Shih, C.-Y.

Publications and source records attributed to Shih, C.-Y..

95 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

On the age of the Onverwacht Group, Swaziland sequence, South Africa

Some rocks of the Onverwacht Group, South Africa, have been analyzed for Rb and Sr concentrations and Sr isotopic composition. These rocks include volcanic rocks, layered ultramafic differentiates and cherty sediments. Whole rock data indicate that the Rb-Sr isotopic systems in many samples were open and yield no reasonable isochron relationships. However, the data of mineral separates from a basaltic komatiite define a good isochron of 3.50 (plus or minus .2) b.y. with an initial Sr-87/Sr-86 ratio of 0.70048 plus or minus 5. The orthodox interpretation of this age is the time of the low grade metamorphism. It is reasonable to assume that the age of 3.50 b.y. might also represent the time of initial Onverwacht volcanism and deposition. The initial Sr-87/Sr-86 ratio obtained above is important to an understanding of the Sr isotopic composition of the Archean upper mantle.

Jahn, B.-M.↗
NASA NTRS1974

Trace element geochemistry of Archean volcanic rocks

The K, Rb, Sr, Ba and rare-earth-element contents of some Archean volcanic rocks from the Vermilion greenstone belt, northeast Minnesota, were determined by the isotopic dilution method. The characteristics of trace element abundances, supported by the field occurrences and major element chemistry, suggest that these volcanic rocks were formed in an ancient island arc system.

Jahn, B.-M.↗
NASA NTRS1974

Chemical evidence for the origin of 76535 as a cumulate

Lunar sample 76535 is a coarse-grained troctolitic granulite. It is characterized by low REE concentrations and a positive Eu anomaly. Its original petrographic character has been disturbed by metamorphic reequilibration. Its chemical characteristics are those of an olivine-plagioclase cumulate. The amount of trapped parent liquid in the rock is estimated to be in the range of 8-16%. The REE concentrations of the parent liquid, if 16%, range from 13 times the chondritic value for Lu to 27 times for La. The parent liquid had no appreciable Eu anomaly.

Haskin, L. A.↗
NASA NTRS1973

Lunar rock types - The role of plagioclase in non-mare and highland rock types

Some nonmare and highland rock types (14310 type KREEP and very high Al2O3 basalts) have the internal chemical variations expected for a plagioclase-liquid system. The observed Eu variations in these rock types suggest a D(Eu) 1/p of 0.6 to 0.7. The Sr variations suggest a D(Sr) 1/p of about 0.6, with values as low as 0.35 suggested for some materials from sample 14063. Common Apollo 14 KREEP and Apollo 15 KREEP do not show internal Sr, Eu, Al2O3 variations consistent with the D(Eu, Sr) 1/p values derived for 14310 type KREEP. Major element and experimental data indicate that olivine or pyroxene is a large, perhaps dominant, controller of chemical variations within common Apollo 14 KREEP. The application of these distribution coefficients to pure anorthosites like 15415 yields the model dependent conclusion that the silicate liquids with which such anorthosites may have been chemically equilibrated have not yet been analyzed and perhaps not directly sampled.

Hubbard, N. J.↗