DOI: 10.5880/fidgeo.2022.035
title: Mineralogical and geochemical data of two weathering profiles in a Mediterranean and a humid climate region of the Chilean Coastal Cordillera

description: This publication provides mineralogical and geochemical data of two 6-m-deep weathering profiles formed from granitic rock. They are located in different climate zones (Mediterranean and humid) and are close to the national parks of La Campana and Nahuelbuta in the Chilean Coastal Cordillera. Additional rock samples from adjacent boreholes were used to relate the regolith to the bedrock. The profiles were sampled in February and March 2020 as part of the German Science Foundation (DFG) priority research program SPP-1803 “EarthShape: Earth Surface Shaping by Biota”. The goal of this project is to obtain a holistic view on the interplay of the geosphere and the biosphere under different climatic conditions and to investigate weathering mechanisms. The aim of this publication is to provide the data basis for understanding the weathering processes that control the development of the profiles in relation to different climatic conditions. To this end, we measured the geochemistry with X-ray fluorescence, extracted Fe, Al and Si with oxalate/dithionite, determined the grain sizes by wet sieving and pipetting, measured the magnetic susceptibility, and analysed the mineral content of bulk samples and clay fractions with X-ray diffraction. The data are compiled in one Excel file and all results of the X-ray diffraction measurements are available as RAW- and TXT files.
description: Two 6-m-deep soil pits were manually dug next to boreholes. These boreholes reached the bedrock of the weathering profiles. Each soil pit was sampled by 20 bulk samples (approx. 3 kg/sample) to cover the entire soil pit profile. These samples were separated with a rotary splitter and sample aliquots were used for 1) grain size determination (sieving and pipetting) and clay separation at the Department of Applied Geochemistry and the Chair of Ecohydrology and Landscape Evaluation (Technische Universität Berlin, Germany), 2) oxalate and dithionite extraction (Fe, Al and Si) at the Chair of Soil Science (Technische Universität Berlin, Germany), 3) X-ray diffraction analysis (XRD) at the Department of Applied Geochemistry (Technische Universität Berlin, Germany), magnetic susceptibility measurements at the Department of Geosciences (University of Tübingen, Germany), and 4) X-ray fluorescence analysis (XRF) by Fluxana® (Bedburg-Hau, Germany). In addition to the soil pits, wireline rotary drilling (PQ3-sized crown; core diameter ~80 mm) with potable water was used to recover core runs of up to 1.5 m length and to reach the bedrock of the weathering profiles. Representative bedrock and weathered rock samples were separated from the core. Bedrock samples were processed like soil pit samples to analyse the bulk geochemistry and mineralogy, and polished sample slabs were geochemically mapped with micro-X-ray fluorescence at the Department of Applied Geochemistry (Technische Universität Berlin, Germany). Additionally, bedrock and weathered rock samples were impregnated with blue-dyed artificial resin and thin-sectioned for light-microscopical and electron microprobe investigations at the Department of Applied Geochemistry (Technische Universität Berlin, Germany) and the German Research Centre for Geosciences (Potsdam, Germany).