1. Department of Earth Sciences; Uppsala University; Villavägen 16 Uppsala 75236 Sweden
2. CNOOC Research Institute; Taiyanggong South Street 6 Beijing 100028 China
3. GFZ German Research Centre for Geosciences; Telegrafenberg 14473 Potsdam Germany
4. Department of Geological Sciences; University of Saskatchewan; Saskatoon S7N 5E2 Canada