Weathering of siderite in the polar conditions

• Autorzy: Figura P. , Manecki M. , Rzepa G.
• Konferencja: XVth International Conference of Young Geologists Her'lany 2014 : Międzybrodzie Żywieckie, Poland, May, 8th-10th 2014
• Języki publikacji: EN

Abstrakty

EN

Rapid retreat and thinning of glaciers perturb balance of polar ecosystems. These processes influence global climate (Anderson et al. 2000, Płonka 2009). For better understanding of changes and their consequences for global climate, it is necessary to extend our knowledge about processes occurring contemporary in the forelands of retreating glaciers. Numerous researches were carried out on this subject (Anderson et al. 1997, Bukowska-Jania et al. 2003, Pulina et al. 2003). For example, upliftdriven climate change hypothesis assumes that decrease of temperature results from regression of glaciers and is connected with chemical denudation of silicate sediments, which acts as a sink of CO2 from the atmosphere (Płonka 2009). Despite of this, many processes and dependences in polar environment are poorly known. Retreating glaciers and high chemical denudation observed in Polar Regions play significant role in weathering of regolith. Fast retreat of many glaciers exposures great amounts of fresh and fine sediment. Weathering of rock-forming minerals is a source of ions in waters as well as secondary minerals and nutrients in initial soils. These issues are object of interest recently because intensified weathering in Polar Regions may affect global cycle of many elements, particularly Fe (Anderson et al. 1997, 2000, Brenasconi 2008). This study is a part of large research, concerning mechanisms, budget and transport of iron from the foreland of fast retreating arctic glacier. The objective of this research is to determine processes and products of siderite weathering in the polar condition. The area of this study is located on the SW part of the Spitsbergen, in the foreland of Werenskioldbreen. It is hypothesized that in Arctic these processes differ significantly from their equivalents in Alpine regions. Field experiment on Spitsbergen lasted eight years. Samples of the siderite were buried in the surface layer of bottom moraine (in the initial polar soils) 100 m, 250 m and 2000 m from glacier front. This represents a chronosequence of sediment uncovered from underneath the glacier ca. 5-, 10-, and 90-years ago. Samples were recovered after 1 year and after 8 years of burial. Optical microscopy in transmitted and reflected light, scanning electron microscopy SEM/EDS and powder X-ray diffractometry were applied to characterize both, control sample and experimental samples. Siderite with manganese substitutions sampled from the outcrops of metamorphic carbonate in the vicinity of Werenskiold glacier was used for the experiment. This resembles mineral fragments eroded and transported by the glacier. Characterization of control sample (siderite before the experiment) indicates that it already exhibits advanced stages of transformation into secondary phases. Secondary minerals include oxides and hydroxides of iron, such as: goethite, hematite and lepidocrocite. The same mineral phases were identified in experimental recovered after burial. Additionally, 8-year sample shows traces of dissolution. Weathering of siderite in polar initial soils in the foreland of retreating glacier leads to formation of secondary goethite, hematite and lepidocrocite. These phases appear to be the most stable products of siderite weathering in this environment. There is no difference between the samples buried in very young and in older, more evolved initial soil. Additionally, transformations of siderite are identical in initial polar soils and in the outcrops of siderite rock. Traces of dissolution noticed on the surface of older samples indicate that part of iron is permanently removed from the system by solutions. This process, probably mediated by microorganisms, requires further investigation.

Słowa kluczowe

EN

global climate; ecosystem; CO2

• Wydawca: Wydawnictwa AGH
• Czasopismo: Geology, Geophysics and Environment
• Rocznik: 2014
• Tom: Vol. 40, no. 1
• Strony: 84--85
• Opis fizyczny: Bibliogr. 6 poz.

Twórcy

autor

Figura P.

• AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry; al. Mickiewicza 30, 30-059 Krakow, Poland

autor

Manecki M.

• AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry; al. Mickiewicza 30, 30-059 Krakow, Poland

autor

Rzepa G.

• AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry; al. Mickiewicza 30, 30-059 Krakow, Poland

Bibliografia

• 1. Anderson S.P., Drever J.I., Frost C.D. & Holden P., 2000. Chemical weathering in the foreland of the retreating glacier. Geochimica et Cosmochimica Acta, 64, 1173-1189.
• 2. Anderson S.P., Drever J.I. & Humphrey N.F., 1997. Chemical weathering in glacial environment. Geology, 25, 399-403.
• 3. Brenasconi S.M., 2008. Weathering, soil formation and initial ecosystem evolution on a glacier forefield: a case study from the Damma Glacier, Switzerland. Mineralogical Magazine, 72, 19-22.
• 4. Bukowska-Jania E., 2003. Rola systemu lodowcowego w obiegu węglanu wapnia w środowisku przyrodnicznym. Wydawnictwo Uniwersytetu Śląskiego, Katowice.
• 5. Płonka A., 2009. Dynamika i mechanizmy przemian minerałów młodych gleb Spitsbergenu jako wyraz ocieplania się klimatu i cofania lodowców. Akademia Górniczo-Hutnicza im. Stanisława Staszica, Kraków.
• 6. Pulina M., Burzyk J. & Burzyk M., 2003. Carbon dioxide in the tundra soils of SW Spitsbergen and its role in chemical denudation. Polish Polar Research, 24, 243-260.