Jean-Marc Baele

Iron microbial mats in modern and phanerozoic environments

The recognition of iron microbial mats in terrestrial environments is of great relevance for the search for extraterrestrial life, especially on mars where significant iron minerals were identified in the subsurface. Most researches focused on very ancient microbial mats (e.g. BIFs) since they formed on Earth at a time where similar conditions are supposed to have prevailed on Mars too. However, environmental proxies are often difficult to use for these deposits on Earth which, in addition, may be heavily transformed due to diagenesis or even metamorphism. Here we present modern and phanerozoic iron microbial mats occurrences illustrating the wide variety of environments in which they form, including many marine settings, ponds, creeks, caves, volcanoes, etc. Contrarily to their Precambrian counterparts, Modern and Phanerozoic deposits are usually less affected by diagenesis and the environmental conditions likely to be better constrained. Therefore, their investigation may help for the search for morphological and geochemical biosignatures (e.g. iron isotopes) in ancient iron microbial occurrences on Earth but also on other Planets. In particular, many of the case studies presented here show that microstromatolithe-like morphologies may be valuable targets for screening potential biosignatures in various rock types.

Systematic REE Partitioning in Cubo-Dodecahedral Fluorite from Belgium Revealed by Cathodoluminescence Spectral Imaging and Laser Ablation-ICP-MS

Geochemistry of the rare earth elements (REE) in fluorite is widely used in ore geology. However, bulk analysis may be biased by compositional heterogeneity in crystals. Here we report a systematic REE partitioning in cubo-dodecahedral fluorite crystals from Belgium using cathodoluminescence (CL) spectral imaging and laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) analysis. The light REE (LREE) are markedly enriched, and heavy REE (HREE) depleted in the |110| sector relative to the |100| sector. The partition coefficient K |110|/|100| is >10 for LREE and <1 for HREE. Very contrasting REE patterns and ratios are thus recorded from the same crystal. CL can be used for imaging compositional heterogeneities since REE are known CL activators in fluorite. However, CL imaging is found of limited application when the REE lines are masked by the strong Eu2+ emission. Spectral imaging of other REE lines solved this problem by producing sharp and contrasted compositional images.

New Integrated High-Resolution Dinoflagellate Cyst Stratigraphy and Litho- and Chemostratigraphy from the Paris and Dieppe-Hampshire Basins for the ''Sparnacian''

The Paris Basin represents an historical cradle of Palaeogene stratigraphy, where during the nineteenth century the Palaeocene Series and the “Sparnacian Stage” were established. As highlighted by Aubry et al. (2005), whereas the chronostratigraphic connotation of the “Sparnacian Stage” has been controversial since its definition, modern studies of the late Palaeocene–early Eocene interval have revealed that the so-called “Sparnacian” deposits encompass a remarkable and short (~170 kyr) episode of the Cenozoic, the Palaeocene–Eocene Thermal Maximum (PETM, ~55.8–55.6 Ma). Dinoflagellate assemblages from the “Sparnacian” of the Dieppe–Hampshire and Paris basins do not contain the key species Apectodinium augustum, whereas it is present in the northern Belgian Basin Tienen Formation and is coeval there with the CIE and the Apectodinium acme interval. However, our calibration of the Apectodinium acme to the CIE in the Dieppe–Hampshire and Paris basins suggests its attribution to the A. augustum zone. The absence of species A. augustum in the Anglo–Paris Basin may be explained by its restriction to more offshore conditions.

Siderite globules associated with fossil microbiota from cretaceous cavity and fracture fillings in Southern Belgium: second known terrestrial analog for the carbonate in Martian meteorite ALH84001?

Recently discovered siderite globules from Upper Cretaceous cavity and fracture fillings in southern Belgium are described and interpreted with emphasis on the still unsolved problem of the carbonates in meteorite ALH84001, which enclose controversal evidence for ancient Martian life. The most interesting aspects of the carbonates described here are 1) their close association with fossil microbiota, 2) their environment, which is 100% sedimentary, subaerial and not hydrothermal and 3) their morphologies, some of which being similar to those in ALH84001. Although the question of the direct biological influence is not critical in this case, the biogenicity for the minerals will be discussed as a strong possibility and is not only inferred from the simple spatial (and temporal) association of the carbonates and the fossil microbiota. Morphological, textural and chemical data will be presented and interpreted as variations in fluid chemistry related to environmental changes. Although they may appear different from those in Martian meteorite and Spitzbergen xenoliths, the Cretaceous globules originated in subsurface environment which left evident traces of life in the form of fossil microbial/fungal mats. They are thus considered as an opportunity to investigate biosignatures in future research using the wide range of available techniques.

Compatibility Assessment for Repair Mortars: An Optimized Cement-Based Mix for Tuffeau de Lincent

Mortars developed for the reconstitution and ‘plastic repair’ of natural stones have become increasingly popular. They are an alternative for the replacement of deteriorated stones, since they are capable of preserving the (memory of) diversity in building materials. This article addresses some key elements for the compatibility between repair mortars and stones. This research accordingly studies the compatibility of a repointing mortar designed for the Tuffeau de Lincent (Belgium), a friable stone in need for restoration and replacement, which was developed using an auto-formulation tool, based on strength and colour compatibility. The selected repointing mortar was further tested in order to assess its use as plastic repair mortar for the Tuffeau de Lincent stone. The developed mortar was considered compatible in colour with the stone and had a strength of 14 MPa, which falls within the strength range of the stone (8–18 MPa). However, porosity and pore size distribution measurements indicated that the stone and the mortar were different. This study compares the first product of the prototype formulation tool and lays the foundations for a more expanded and larger auto-formulation tool for the repair of natural stone.

Advances in the Assessment of the Deep Geothermal Reservoirs of Hainaut, Belgium

In the urbanised area of Mons-Borinage (Hainaut, SW Belgium), deep geothermal potential is known since the late seventies. Since 1986, the resource is exploited by two wells. Current projects aim at developing this resource near Mons city for heat production, but also using a suspected deeper reservoir for electricity production. The development of deep geothermal projects in Hainaut requires a better knowledge of the structure of the reservoirs. For this purpose, a new geophysical survey (2D reflection seismic lines) was conducted in 2012, and data from old surveys were reprocessed. Distinctive discontinuities were expected, according with the regional tectonic framework. Based on our interpretation of the final seismic sections, main geological horizons were picked (in TWT) and integrated in a 3D geological model.