# Provenance and Paleo-Environment of the Late Carboniferous Bauxite Formations in Southern Shanxi
## 3 Sample Collection and Test  
The Pinglu bauxite rock strata can be vertically divided into three parts, namely, from bottom to top, iron-aluminum rock, bauxite, and clay rock (locally transformed into coal seams). In order to further study its sedimentary paleoenvironment and provenance characteristics, two representative profiles were selected. A total of 20 samples (Figure 3c) were selected from the typical profiles (Jinyu and Jinshi profile) of Pinglu mine area. The samples comprised claystone, bauxite, and coal and sandstone. From top to bottom, eleven samples were obtained from the Jinyu profile (Y1-Y11, Figure 3a), and nine from the Jinshi profile (S1-S9, Figure 3b).  
Figure 3: Field photographs (**a**,**b**) and section map (**c**) of the Pinglu aluminiferous rock series.  
Microscopic optical, X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) analyses were conducted to determine the mineralogical and geochemical characteristics of the samples accurately. Microscopic optical observations were conducted at the Geological Experimental Center of Taiyuan University of Technology using a Leica 2700P microscope. Whole-rock XRD was performed at the Analytical Testing Center of Taiyuan University of Technology, using a PANalytical Aeris instrument Netherlands, Cu-Ka radiation, a graphite monochromator, and continuous scanning applying the following settings: 40 kV voltage, 80 mA beam current, 6.5\({}^{\circ}\)/min scanning speed, and a scanning range of 5\({}^{\circ}\)-70\({}^{\circ}\) under an ambient temperature of 18 \({}^{\circ}\)C and 30% humidity. The software Jade 6.5 was used to match the main diffraction peaks (d-value and intensity) with standard cards to determine the main mineral phase composition.  
Elemental geochemical analysis was performed at the Analytical Testing Research Center of the Beijing Research Institute of Uranium Geology. Major element analysis was carried out at 24 \({}^{\circ}\)C and 24% humidity, adhering to the standards GB/T 14506.14-2010 [28] (Suitable for the determination of ferrous oxide content in silicate rocks, and also applicable for the determination of ferrous oxide content in soil and fluvial sediments.) \"Methods for Chemical Analysis of Silicate Rocks Part 14: Determination of Ferrous Oxide Content\", GB/T14506.34-2019 [29] (Suitable for the gravimetric determination of loss on ignition in soil and sediment samples.) \"Methods for Chemical Analysis of Silicate Rocks Part 34: Determination of Loss on Ignition by Gravimetric Method\", and YS/T 575.23-2021 [30] (Suitable for the determination of Al\({}_{2}\)O\({}_{3}\) SiO\({}_{2}\), Fe\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), K\({}_{2}\)O, MgO, CaO, MnO and P\({}_{2}\)O\({}_{5}\) content in bauxite.) \"Chemical Analysis Methods of Bauxite Part 23: Determination of Element Content by X-ray Fluorescence Spectroscopy\". The XRF fusion method was used, employing the wavelength-dispersive X-ray fluorescence spectrometers AB104L and AXIOS-MAX.  
Trace and rare earth element (REE) analyses were performed at 24.5 \({}^{\circ}\)C and 45% humidity, following the standard GB/T14506.30-2010 [31] (Suitable for silicate rock, like Li, Be, Sc and other 41 elements determination, also suitable for the determination of the above elements in soil, sediment samples.) \"Methods for Chemical Analysis of Silicate Rocks Part 30: Determination of 44 Elements,\" using a mixed acid digestion ICP-MS method and an ELEMENT XR plasma mass spectrometer.