An occurrence of apatite-rich rocks of carbonatitic affinity near the Jotnian graben structure in Gävle, central Sweden
作者:
JanOlov Nyström,
Nils-Bertil Svensson,
Göran Åberg,
期刊:
Geologiska Föreningen i Stockholm Förhandlingar
(Taylor Available online 1985)
卷期:
Volume 107,
issue 3
页码: 185-195
ISSN:0016-786X
年代: 1985
DOI:10.1080/11035898609453053
出版商: Taylor & Francis Group
关键词: Apalite;carbonatite;carbonatitic affinity;graben structure;strontium isotope data;sub-Jotnian;Jotnian;Främlingshem;Gävle;Alnö;central Sweden;N6030;N6031;E1655;E1656
数据来源: Taylor
摘要:
An occurrence of apatite-rich rocks of carbonatitic affinity at Främlingshem, SW of Gävle, central Sweden, is reported. Boulders and cobbles of two lithologically related types (dominated by apatite-calcite and chlorite-apatite, respectively) have been found. Major constituents are fluorapatite with a87Sr/86Sr ratio of 0.7027, Sr-rich calcite (2600 ppm) with (δ13C = -3.9 ± 0.2% vs PDB and δ18O = 14.9 ± 0.5% vs SMOW, chlorite completely replacing biotite or phlogopite, and fragments of granitoids and other rocks. The apatite-rich rocks were apparently emplaced as a ‘crystal-mush’, at a low temperature. They are post-Svecokarelian in age, probably formed between 1750 Ma and 1100 Ma ago, a timespan comprising two or more periods of tensional movements in central Sweden. The location of the Främlingshem rocks near a graben structure is consistent with their carbonatitic affinity.
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