Relationship between mineralogy and the physico-chemical properties of till in central Finland

The chemical and physical characteristics of the fine fraction of till were examined in the area of the Raahe-Ladoga metallogenic belt in central Finland. Till, weathered bedrock and rock samples were collected from the area, where element concentrations of till abruptly ranged from high in an anoma...

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Main Authors: M.L. Räisänen, M. Tenhola, J. Mäkinen
Format: Article
Language:English
Published: Geological Society of Finland 1992-06-01
Series:Bulletin of the Geological Society of Finland
Subjects:
Online Access:http://www.geologinenseura.fi/bulletin/Volume64/sgs_bt_064_1_pages_035_058.pdf
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spelling doaj-8c1a41445ad44405afec2b183ab8ab0f2020-11-24T23:39:03ZengGeological Society of FinlandBulletin of the Geological Society of Finland0367-52111799-46321992-06-01641355810.17741/bgsf/64.1.004Relationship between mineralogy and the physico-chemical properties of till in central FinlandM.L. RäisänenM. TenholaJ. MäkinenThe chemical and physical characteristics of the fine fraction of till were examined in the area of the Raahe-Ladoga metallogenic belt in central Finland. Till, weathered bedrock and rock samples were collected from the area, where element concentrations of till abruptly ranged from high in an anomalous zone (NE) to low in a non-anomalous zone (SW). The grain size distribution, specific surface area and unit weight, and the leachability of elements measured with several chemical methods were determined from the fine fraction (<0.06 mm) of till. The mineralogical composition of the fine fraction of till and weathered bedrock was established with the X-ray diffraction method (XRD), and the chemical composition of rock samples with the X-ray fluorescence method (XRF). The main factor affecting the increased element concentrations in the anomalous zone is the variation in mica and clay mineral types. The abundance of trioctahedral micas (biotite) and vermiculitic clays carrying most of the trace metals dissolved in aqua regia, has affected to the geochemical pattern of till in the study area. The concentrations of trace metals in the iron precipitates extracted with acid oxalate were too low to be used as evidence of the hydromorphic origin of the anomalous zone. The abundance of main silicates (quartz, feldspars) does not vary much in the fine fraction of till throughout the study area. The absence of the swelling smectite component from the surface layers of till indicates that the source was not the underlying weathered bedrock. The till with a vermiculitic mixed-layer mineral in the anomalous zone contains more material from old sediments weathered during interstadial or interglacial time than does the till with a low clay content in the non-anomalous zone. The abrupt change in the mineralogical and physical properties of till in the study area is suggested to be attributed to the difference in the transport and accumulation dynamics of overburden during deglaciation. http://www.geologinenseura.fi/bulletin/Volume64/sgs_bt_064_1_pages_035_058.pdfgeochemistrytillclay mineralogymica groupweatheringspecific surfaceunit weightbedrockcentral Finland
collection DOAJ
language English
format Article
sources DOAJ
author M.L. Räisänen
M. Tenhola
J. Mäkinen
spellingShingle M.L. Räisänen
M. Tenhola
J. Mäkinen
Relationship between mineralogy and the physico-chemical properties of till in central Finland
Bulletin of the Geological Society of Finland
geochemistry
till
clay mineralogy
mica group
weathering
specific surface
unit weight
bedrock
central Finland
author_facet M.L. Räisänen
M. Tenhola
J. Mäkinen
author_sort M.L. Räisänen
title Relationship between mineralogy and the physico-chemical properties of till in central Finland
title_short Relationship between mineralogy and the physico-chemical properties of till in central Finland
title_full Relationship between mineralogy and the physico-chemical properties of till in central Finland
title_fullStr Relationship between mineralogy and the physico-chemical properties of till in central Finland
title_full_unstemmed Relationship between mineralogy and the physico-chemical properties of till in central Finland
title_sort relationship between mineralogy and the physico-chemical properties of till in central finland
publisher Geological Society of Finland
series Bulletin of the Geological Society of Finland
issn 0367-5211
1799-4632
publishDate 1992-06-01
description The chemical and physical characteristics of the fine fraction of till were examined in the area of the Raahe-Ladoga metallogenic belt in central Finland. Till, weathered bedrock and rock samples were collected from the area, where element concentrations of till abruptly ranged from high in an anomalous zone (NE) to low in a non-anomalous zone (SW). The grain size distribution, specific surface area and unit weight, and the leachability of elements measured with several chemical methods were determined from the fine fraction (<0.06 mm) of till. The mineralogical composition of the fine fraction of till and weathered bedrock was established with the X-ray diffraction method (XRD), and the chemical composition of rock samples with the X-ray fluorescence method (XRF). The main factor affecting the increased element concentrations in the anomalous zone is the variation in mica and clay mineral types. The abundance of trioctahedral micas (biotite) and vermiculitic clays carrying most of the trace metals dissolved in aqua regia, has affected to the geochemical pattern of till in the study area. The concentrations of trace metals in the iron precipitates extracted with acid oxalate were too low to be used as evidence of the hydromorphic origin of the anomalous zone. The abundance of main silicates (quartz, feldspars) does not vary much in the fine fraction of till throughout the study area. The absence of the swelling smectite component from the surface layers of till indicates that the source was not the underlying weathered bedrock. The till with a vermiculitic mixed-layer mineral in the anomalous zone contains more material from old sediments weathered during interstadial or interglacial time than does the till with a low clay content in the non-anomalous zone. The abrupt change in the mineralogical and physical properties of till in the study area is suggested to be attributed to the difference in the transport and accumulation dynamics of overburden during deglaciation.
topic geochemistry
till
clay mineralogy
mica group
weathering
specific surface
unit weight
bedrock
central Finland
url http://www.geologinenseura.fi/bulletin/Volume64/sgs_bt_064_1_pages_035_058.pdf
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