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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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