Albert Gilg

Technical University of Munich

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Marina Rosas‐Carbajal

Institut de physique du globe de Paris

Léon Dejonghe

Institute of Natural Sciences

Thierry Reuschlé

Centre National de la Recherche Scientifique

Patrick Baud

Université de Strasbourg

Michael J. Heap

Université de Strasbourg

Claire E. Harnett

University College Dublin

V. Coppola

University of Naples Federico II

Jean‐Christophe Komorowski

Institut de physique du globe de Paris

Maria Boni

University of Naples Federico II

Bernhard Schulz

TU Bergakademie Freiberg

Cooperative Institutions

Centre National de la Recherche Scientifique

Institut de physique du globe de Paris

Université Paris Cité

Université de Strasbourg

University of Edinburgh

Institut Terre & Environnement de Strasbourg

Institut de Physique

École Polytechnique Fédérale de Lausanne

University of Naples Federico II

Terre des Hommes

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Intensive Chemical Weathering in the Arctic During the Miocene Climatic Optimum

Adrian M. Hall Dan N. Barfod Albert Gilg Finlay M. Stuart Pertti Sarala

The Arctic today has shallow, chemically immature, and frost-dominated weathering regimes. At Sokli, Finland (68˚N), a 70 m deep palaeo-weathering profile is developed in a Devonian carbonatite pipe that represents fundamentally different past weathering environments. Formation of the apatite-francolite P-ore likely began under Palaeogene warm, humid climates. Later, cryptomelane (K-Mn oxide) crusts developed within the ore that have yielded peak 40Ar/39Ar ages of 16.20 ± 0.13 Ma (2s)., The crusts formed at the redox front during the Miocene Climatic Optimum (~16.9–14.7 Ma) under mean annual temperatures ~12-14˚C warmer than today. The presence of the crust at shallow depth (15 m) indicates very low erosion rates since formation, consistent with its position on a tectonically stable Archaean craton and in the cold-based ice divide zone of successive Fennoscandian ice sheets. The Miocene Climatic Optimum triggered a pulse of intensive weathering in mid- and low latitudes; the Sokli cryptomelane ages demonstrate that intensive chemical weathering extended into the Arctic.

10.2139/ssrn.4572481

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The influence of water-saturation on the strength of volcanic rocks and the stability of lava domes

Michael J. Heap Claire E. Harnett Jamie Farquharson Patrick Baud Marina Rosas‐Carbajal

The rocks forming a volcano are typically saturated or partially-saturated with liquid. However, most experiments aimed at better understanding the mechanical behaviour of volcanic rocks have been performed on dry samples, and therefore most large-scale models designed to explore volcanic stability have used parameters representative for dry rock. We present a combined laboratory and modelling study in which we (1) quantify the influence of water on the mechanical behaviour of variably altered dome rocks from La Soufrière de Guadeloupe (Eastern Caribbean) and (2) use these new laboratory data to investigate the influence of water on dome stability. Our laboratory data show that the ratio of wet to dry uniaxial compressive strength (UCS) and Young's modulus are ~0.95–0.30 and ~1.00–0.10, respectively. In other words, the rocks were all weaker when saturated with water. We also find that the ratio of wet to dry UCS decreases with increasing alteration (the wt% of secondary minerals). Micromechanical modelling suggests that the observed water-weakening is the result of a decrease in fracture toughness (KIC) in the presence of water. We also find that the ratio of wet to dry KIC decreases with increasing alteration, explaining why water-weakening increases with alteration. To explore the influence of water saturation on dome stability, we numerically generated lava domes using the experimental data corresponding to dry unaltered and altered rock, in Particle Flow Code. The strength of the dome-forming rocks was then reduced to values corresponding to wet conditions. Our modelling showed that, although the stability of the unaltered dome was not influenced by water saturation, large displacements were observed for the altered dome. Additional modelling in which we modelled a buried alteration zone within an unaltered dome showed that higher displacements were observed when the dome was water saturated. We conclude that (1) the presence of water reduces the UCS and Young's modulus of volcanic rock, (2) larger decreases in UCS in the presence of water are observed for altered rocks, and (3) large-scale dome stability modelling suggests that the stability of a dome can be compromised by the presence of water if the dome is altered or contains an altered zone. These conclusions highlight that the degree of alteration and water saturation should be monitored at active volcanoes worldwide, and that large-scale models should use values for water-saturated rocks when appropriate.

Dome (geology)

Saturation (graph theory)

Lava dome

10.5194/egusphere-egu23-1248

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Two-stage prograde and retrograde Variscan metamorphism of glaucophane-eclogites, blueschists and greenschists from Ile de Groix (Brittany, France)

International Journal of Earth Sciences (2001)

Bernhard Schulz Claude Triboulet Claude Audren Hans‐Rudolf Pfeifer Albert Gilg

Glaucophane

Blueschist

Amphibole

10.1007/s005310000156

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STATE OF THE ART ON THE "CALAMINE"-TYPE ZINC DEPOSITS OF BELGIUM

Geologica Belgica (2007)

Maria Boni Léon Dejonghe C. Ballasone V. Coppola Albert Gilg

The Belgian “Calamine”-type nonsulphide Zn deposits, mainly located in the Verviers Synclinorium in the northeastern part of the country, represent the historical basis for zinc mining and smelting industry in Europe. The most important was the La Calamine orebody (more than 600,000 tons of Zn metal) that was continuously exploited for several centuries. Nonsulphide ores associated to sulphides, were also exploited at Schmalgraf, Engis, Dickenbusch, Fossey, Rocheux-Oneux, Welkenraedt and other smaller deposits (Dejonghe, 1998). Across the border to Germany, in the north Eifel, similar Zn-Pb deposits as the Belgian ones (also consisting of both primary sulphides and calamines) were exploited in the past in the Aachen-Stolberg district, but their economic potential was much lower than in Belgium. The primary Zn-Pb sulphide mineralization consists of post-Variscan hydrothermal veins and replacementand breccia bodies (Fig. 1A), mostly occurring at the top of

Syncline

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Data for Heap et al. (JGR: Solid Earth)

Figshare (2021)

Michael J. Heap Tobias Baumann Marina Rosas‐Carbajal Jean‐Christophe Komorowski Albert Gilg

Mechanical data accompanying Heap et al. (JGR: Solid Earth). In the file name, "uni" and "trx" stand for uniaxial and triaxial, respectively. The first number in the file name is the block number (e.g., H2A), and the second number is the sample number (e.g., 2). Finally, "d" and "w" stand for dry and wet, respectively.
In the uniaxial files:Temps(s) - time in secondssigV(MPa) - axial stress in MPaDefcapt - axial strain from LVDTDefax - axial strain from strain gage (not used here)Defrad - radial strain from strain gage (not used here)Defvol - volumetric strain from strain gage (not used here)
Deplctcapt(um) - axial displacement in microns
In the triaxial files:
Temps(s) - time in seconds
Pc(MPa) - confining pressure in MPaPax(MPa) - axial stress in MPaPpam(MPa) - pore fluid pressure in MPaQ(MPa) - differential stress in MPaPmoy(MPa) - effective mean stress in MPaDefaxcapt - axial strain from LVDTDefvolfluide - sample porosity changeDefvolconf - change in confining fluid volume in cm2Deplct(um) - axial displacement in microns

Heap (data structure)

Solid earth

10.6084/m9.figshare.14701137

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Characterization of the nonsulfide deposits ("Calamine") of Belgium

V. Coppola Maria Boni Albert Gilg G. Ballassone Léon Dejonghe

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Mineralogy and Geochemistry of the Sedimentary Kaolin Deposits From Sinai, Egypt: Implications for Control by the Source Rocks

Clays and Clay Minerals (2012)

Hassan Baioumy Albert Gilg Heinrich Taubald

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10.1346/ccmn.2012.0600608

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Citations (22)