Chemical weathering on Eldsfjellet, Meland municipality, western Norway Oliver Queck Master Thesis in Geology – Quaternary Geology and Paleoclimatology Department of Earth Science University of Bergen Autumn 2012 Acknowledgment I would like to thank my supervisor Henriette Linge for her constructive ideas during field work, laboratory work and the writing process. I also want to thank Prof. Haakon Fossen and Prof. Ingunn H. Thorseth for their supervision. A big thanks goes to Prof. Svein-Olaf Dahl, Henrik Løset Jansen and Bjørn Eikeland for helping me to collect sediment samples from Storatjørna (local lake). Special thanks go to Dr. Romain Meyer for his guidance in the laboratory and the help with analysing my results. I want to thank Ole Tumyr, Hildegunn Almelid, Yuval Ronen and Siv Hjort Dundas for the help with preparing and processing my samples. For the clay analysis of my sediment samples I want to thank Markus Peltz and Dr. Georg Grathoff at the University of Greifswald (Germany). Big thanks also go to Benjamin Aubrey Robson for reading through my thesis and correcting my English. I am very thankful for always having the support of my parents, my friends and my girlfriend during my thesis. Without them it would have been much harder to write this thesis. Bergen, November 2012 Oliver Queck Abstract The Subject of this master thesis was to define the chemical weathering processes, create a weathering chain from sink to source and to evaluate the degree of weathering on Eldsfjellet, Meland municipality in western Norway. Rock, water and sediment samples were collected in the field area using a corer for hard rock and sediment samples, water samples were bottled in laboratory flasks and afterwards cleaned with a filter to remove colloids and other particles. Multiple analyses such as XRF, XRD, ICP-MS, ICP-OES and microscopy were carried out. The major element, trace element and rare earth element composition of the various samples were acquired. The comparison between trace elements from water and rock samples showed a good agreement which leads to the presumption that water is the major weathering and transport agent in the field area. Because of the low temperature range between summer and winter in the field area, mechanical weathering is assumed to be a less important weathering factor for most of the year. Derived sediment samples from organic rich top layers in the local catchment lake were analysed using XRD. Clay minerals were found which could be directly linked to the local bedrock, therefore it was possible to create a weathering chain. First the bed rock is slowly dissolved due to the permanent supply with fresh water. Secondly, because of the reaction between water and bedrock, clay minerals get produced which then will be, together with other particles, transported to the local catchment lake and finally deposited in the lake sediments. To determine the degree of weathering, different chemical indexes of weathering have been used, all of which show a slight level of weathering. The Elsdfjellet data were compared with data on similar rock types from India, which shows that climatic difference (higher temperature, more precipitation) and a longer transport distance favour chemical weathering in India. To define weathering rates, a formula was used which includes a gain-loss factor calculated from the weight % concentration of different major elements in bedrock and sediment samples. The calculation also displays a low loss of fresh rock material. Contents Acknowledgment ....................................................................................................................................... 1. Introduction ..................................................................................................................................... 1 1.1. Study site ................................................................................................................................. 3 1.2. Bedrock geology ...................................................................................................................... 4 1.3. Geomorphology and sediment cover ...................................................................................... 6 1.4. Present weather conditions .................................................................................................... 8 1.5. Quaternary geology ................................................................................................................. 9 2. Theory and definitions .................................................................................................................. 13 2.1.1. Chemical weathering ..................................................................................................... 13 2.1.2. Mechanical weathering ................................................................................................. 15 2.2. Factors that affect weathering .............................................................................................. 16 2.2.1. Climate ........................................................................................................................... 16 2.2.2. Frost ............................................................................................................................... 17 2.2.3. Aspect ............................................................................................................................ 17 2.2.4. Atmospheric pollution ................................................................................................... 18 2.3. Mineral weathering ............................................................................................................... 18 2.3.1. Crystal size ..................................................................................................................... 18 2.3.2. Crystal shape ................................................................................................................. 18 2.3.3. Crystal perfection .......................................................................................................... 19 2.3.4. Access for weathering agents and removal of weathering products ............................ 19 2.4. Weathering of rock forming minerals ................................................................................... 20 2.4.1. Feldspar ......................................................................................................................... 20 2.4.2. Pyroxene ........................................................................................................................ 20 2.5. Clay minerals ......................................................................................................................... 20 2.5.1. Structures of clay minerals ............................................................................................ 21 2.5.2. Properties of clay minerals ............................................................................................ 21 2.5.3. Weathering of clay minerals.......................................................................................... 22 2.6. Corona textures ..................................................................................................................... 23 3. Methodology ................................................................................................................................. 27 3.1. Fieldwork techniques ............................................................................................................ 27 3.1.1. Drilling ........................................................................................................................... 27 3.1.2. HTH sediment corer ....................................................................................................... 28 3.1.3. Water samples ............................................................................................................... 29 3.2. Laboratory methodology ....................................................................................................... 29 3.2.1. Rock sample preparation............................................................................................... 29 3.2.2. Sediment sample preparation ....................................................................................... 32 3.2.3. Preparation of water samples ....................................................................................... 32 3.3. Geochemical analysis ............................................................................................................ 33 3.3.1. X-ray fluorescence spectroscopy ................................................................................... 33 3.3.2. ICP-MS ........................................................................................................................... 33 3.3.3. ICP-OES .......................................................................................................................... 36 3.3.4. Polarized light microscopy ............................................................................................. 38 3.3.5. SEM-scanning electron microscope .............................................................................. 38 3.4. Evaluation of measurement precision .................................................................................. 39 3.5. Potential Uncertainties for fieldwork and laboratory methods ...........................................