1. Geological Institute, Energy and Mineral Resources Group RWTH Aachen University Wüllnerstr. 2 Aachen 52062 Germany
2. Institute of Geosciences Kiel University Ludewig‐Meyn‐Str 10 Kiel 24118 Germany
3. Geotechnology Research Center Indonesian Institute of Sciences Kompleks LIPI Jl. Sangkuriang Bandung 40135 Indonesia
4. Institute of Geology and Geochemistry of Petroleum and Coal RWTH Aachen University Lochnerstr. 4‐20 Aachen 52056 Germany