کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9461157 | 1312686 | 2005 | 25 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Glacial dispersal studies using indicator minerals and till geochemistry around two eastern Finland kimberlites
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
زمین شناسی اقتصادی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Glacial dispersal studies using indicator minerals and till geochemistry around two eastern Finland kimberlites Glacial dispersal studies using indicator minerals and till geochemistry around two eastern Finland kimberlites](/preview/png/9461157.png)
چکیده انگلیسی
Diamondiferous kimberlites occur in eastern Finland, in the areas of Kaavi-Kuopio and Kuhmo. Active diamond exploration has been ongoing in the country for over two decades, but the Karelian craton still remains under explored given its size and potential. In order to develop techniques that can be applied to diamond exploration in glaciated terrains, the Geological Survey of Finland (GTK) carried out a detailed heavy mineral and geochemical survey of Quaternary till in 2001-2003 around two of the known kimberlitic bodies in Finland, Pipe 7 in Kaavi and Dyke 16 in Kuhmo. The mineralogical and geochemical signatures of these two kimberlites were studied in the basal till deposited down-ice from the targets. The kimberlites were selected to represent two different types in terms of shape, size, age and petrology, as well as showing contrasting country rocks and Quaternary deposits. Till samples up to 60 kg in weight were taken by excavator and by drill rig. Kimberlitic indicator mineral grains (0.25-1.0 mm) were concentrated using a GTK modified 3â³Knelson Concentrator. Fine fractions (<Â 0.063 mm) of selected samples were analyzed by XRF and ICP-MS. The indicator grains down-ice from Pipe 7 form a well-defined fan in the basal till that can be followed for at least 2 km with a maximum concentration at 1.2 km distance from the pipe. Another kimberlitic body discovered during the study 300 m down-ice from Pipe 7 demonstrates that there are in fact at least two superimposed indicator fans. The results do not rule out the possibility of even more undiscovered kimberlitic sources in the area. In contrast, the indicator dispersal trail from Dyke 16 is shorter (â¼1 km) and less well-defined than that at Kaavi, mainly due to the lower indicator content in the kimberlite itself and subsequently in till, as well as a large population of background chromites in till. The latter population is likely having been derived from the Archean Näätäniemi serpentinite massif and the associated ultramafic metavolcanics of the Kuhmo greenstone belt, located ca. 30 km up-ice from the sampling area. The indicator maximum at Seitaperä dyke swarm occurs immediately down-ice from the kimberlite, after which the concentration drops rapidly. Results of this study contribute to the overall understanding of the Quaternary history of the Kaavi and Kuhmo areas, and more importantly, provide key information to diamond exploration in these particular regions and also elsewhere in glaciated terrains.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Geochemical Exploration - Volume 87, Issue 1, October 2005, Pages 19-43
Journal: Journal of Geochemical Exploration - Volume 87, Issue 1, October 2005, Pages 19-43
نویسندگان
M.L. Lehtonen, J.S. Marmo, A.J. Nissinen, B.S. Johanson, L.K. Pakkanen,