Organic Compounds and Conditioning Films Within Deep Rock Fractures of the Äspö Hard Rock Laboratory, Sweden

Abstract

Palaeoproterozoic grano-dioritic rocks of the island of Äspö exhibit several mineralized fracture generations mainly filled by quartz, calcite, fluorite and/or epidote. Manganese-rich calcite fractures of probably Palaeozoic age are related to younger, possibly Pleistocene/Holocene cracks formed during the last ice age and successive crustal uplift, in contact to the host rock, which are sometimes associated with organic matter. Signals of organic molecules could be gained on the corresponding phase boundaries with Raman spectroscopy, likewise HPLC and HPAE-PAD reveal the presence of carbohydrates and amino acids in bulk rock samples. It is supposed that most of the preserved organic matter is related with thin conditioning films. Extracted bacterial and fungal DNA from the grano-dioritic rocks indicates still active microbial activity in fracture micro-niches.

Keywords:

• amino acids
• Äspö, biofilms
• Biosignatures
• conditioning films
• DNA
• granodiorite
• microbe-mineral interface
• Raman spectroscopy
• Subterranean environment

Acknowledgments

We are grateful to the staff of the Äspö HRL as well as the SKL Nova FoU for technical and logistic support. We greatly acknowledge Dr. Christine Heim, Prof. Volker Thiel, Dr. Andreas Reimer (all Geobiology, Göttingen), Dr. Klaus Simon (Geochemistry, Göttingen) and Dr. Martin Blumenberg (Federal Institute for Geosciences and Natural Resources-BGR, Hannover) for valuable critical comments and technical support.

Funding

This study received financial support from the German Research Foundation (DFG – FOR 571; publication #48, Re 665/27-3).