Tracing fossil bio-signals in young to ancient ophiolites

The purpose of this project is to trace signals that may indicate former biomediated alteration of originally glassy volcanic rocks (pillow lavas and hyaloclastites) of former oceanic crust, i.e. ophiolites. We intend to utilize bio-signals worked out for in-situ oceanic crust to fossil oceanic crust, in a complimentary way, and address questions on the relationship between various geological aspects and biological influence. We particularly focus on the earliest traces of bioalteration in volcanic rocks, and at which stage bio-traces may get destroyed or may survive metamorphic and tectonic processes. The bio-traces in former glassy volcanic rocks are: stable isotopes (carbon) signatures, occurence of typical bio-elements (carbon, nitrogen, phosphorus, sulphur) and certain trace elements, as well as typical bio-generated textures. For this purpose eigh t ophiolite terranes have been chosen for investigation and sample collection. These ophiolites are of the widest possible age range (from 90 Ma to 3.5 Ga), they formed during different spreading conditions (slow, intermediate to fast), and they have undergone different metamorphis grades ranging from unmetamorphosed through greensc hist-, blueschist-, into eclogite-facies. In addition to the field-based investigation, experimental work will be conducted to through light on the behaviour of organic matter during metamorphism.