A palaeomagnetic study of Svecokarelian basic rocks from northern Sweden
作者:
Sten-ÅKe Elming,
期刊:
Geologiska Föreningen i Stockholm Förhandlingar
(Taylor Available online 1985)
卷期:
Volume 107,
issue 1
页码: 17-35
ISSN:0016-786X
年代: 1985
DOI:10.1080/11035898509452608
出版商: Taylor & Francis Group
关键词: Svecokarelian;palaeomagnetism;AF-demagnetization;thermal-demagnetization;physical properties;mineralogy;basic rocks;Haparanda Suite;Notträsk;Sangis;Tärendö;Svappavaara;Vittangi;Dundret;north Sweden;N6550 N6740 E2035 E2330
数据来源: Taylor
摘要:
This palaeomagnetic investigation comprises basic rocks from six localities from the Svecokarelian zone in northern Sweden. Most of the pole positions in this study and other reported poles of Svecokarelian and post-Svecokarelian rocks fall within an approximately 12 degrees wide band running from east to west representing ages of magnetizations from 1880-1700 to ∼ 1530 Ma. Thermal demagnetizations of specimens of the probably oldest massifs indicate a possible backward continuation of the polar wandering path. Mineralogical studies of thin sections of the rocks show ore symplectites and myrmekitic textures indicating a slow rate of cooling at least at the end of the rock formation. Signs of metamorphism are demonstrated by the existence of secondary minerals, including magnetite, not related to late magmatic alterations. The distribution of site means as well as the change of directions of the remanence vectors during thermal demagnetization can be explained by a slow rate of cooling and where signs of metamorphism exist by partial remagnetization of the rock. This study has, apart from the palaeomagnetic results, demonstrated the difficulty of correlating radiometric ages with ages of magnetization.
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