THE GEOCHEMISTRY OF THE RADIOACTIVE ELEMENTS IN THE PEGMATITE FIELD OF NORTHERN KARELIA IN RELATION TO THE PROBLEMS ON THE AGE OF THE BELOMORSKIYE (WHITE SEA) INTRUSIONS
Journal Article
·
· Trudy Radievogo Inst. im. V.G. Khlopina
OSTI ID:4179822
>The distribution of U and Th in the rocks of the pegmatite field, as well as in the pegmatite veins themselves, is discussed. The paragenetic relations of the radioactive minerals and the processes of their subsequent alteration were studied. The latest crystallization of radioactive minerals did not occur in the micrecline-quartz veins. The sequence of mineral growth in the Chernaya Salma pegmatite veins is given. The paragenetic association separated from a pegmatitic melt out of which the principal mass of feldspar and quartz had earlier crystallized. The study of the mineral association and of the chemical composition of the mineral series attests to the importance of geochemical differentiation. This process led to considerable segregation, even of those elements which are distinctive in the formation of the overall crystallochemical structure. Although Th everywhere exceeds U in quantity, only rarely does it diverge from the ratio of the average content in the earth's crust. All the varieties of uraninite studied, which crystallized in various enviromnents and formed in five different pegmatite veins, show a considerable constancy in the lead ratio. From the data on radioactivity in the pegmatites of northern Karelia, it must be assumed that the pegmatites are older than the post-Bothnian epoch. Their age has been determined to be on the order of 1800 x 10/sup -6 years, which places them among the oldest Precambrian rocks in the world. (TCO)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-14-008612
- OSTI ID:
- 4179822
- Journal Information:
- Trudy Radievogo Inst. im. V.G. Khlopina, Journal Name: Trudy Radievogo Inst. im. V.G. Khlopina Vol. Vol: 5, Pt. 2
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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