U-Pb zircon and Rb-Sr whole-rock and mineral ages of Proterozoic intrusives on mapsheet Lannavaara, north-eastern Sweden
作者:
Torbjörn Skiöld,
期刊:
Geologiska Föreningen i Stockholm Förhandlingar
(Taylor Available online 1979)
卷期:
Volume 101,
issue 2
页码: 131-137
ISSN:0016-786X
年代: 1979
DOI:10.1080/11035897909452570
出版商: Taylor & Francis Group
关键词: U-Pb;Rb-Sr;dates;absolute age;whole rock;isochrons;zircon;granodiorite;gabbro;supracrustal rocks;metamorphism;scapolitization;intrusions;stratigraphy;Proterozoic;Lannavaara;Norrbotten;north-eastern Sweden;N6811 N6820 E2253 E2152
数据来源: Taylor
摘要:
Radiometric data for igneous rocks, intruding early Proterozoic supracrustals, from two separate areas in north-eastern Sweden are presented. U-Pb analyses on zircons from plutonic rocks of intermediate composition around Lake Paittasjärvi yield an age of 1880 ± 28 Ma. A whole-rock isochron age of 1915± 145 Ma and a plagioclase-hornblendemica age of 1550± 40 Ma are calculated for the same rocks with the Rb-Sr method. Correlated granitoids from the Juoloyanjarvet area, which in part have suffered replacement of plagioclase by scapolite and are intruded by gabbros and younger granites, give a whole-rock Rb-Sr reference line of 1705 Ma and mineral ages of 1535 and 1495 ± 30 Ma. The whole-rock age probably lacks direct geological significance but the mineral ages obtained from both of the above areas may reflect influences from younger plutonism on the dated rocks. One of the intruding gabbros has a Rb-Sr mineral age of 1617 ± 107 Ma. This figure is considered a minimum age of the rock. The impact of scapolitization on the calculated ages is discussed. Decay constants recommended by the IUGS Subcommission on Geochronology (1977) have been used in the calculation of the Rb-Sr and U-Pb ages, which are given at the 95% confidence level.
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