Drops loaded in calcium ions detach from stalactites and impact the underlying stalagmites, thereby allowing these latter to grow through calcite precipitation. Nevertheless, little is known about the influence of the drop free fall and splash dynamics on stalagmite shape and width. Through high-speed imaging of impacting drops on stalagmites from several caves, we observed that the impact point position of the drops is scattered, sometimes over several centimetres. We show that this dispersal has no external cause and must, therefore, be self-induced. Using a Langevin-like equation, we then propose a prediction of the impact point dispersal as a function of the falling height travelled by the drops. We finally show that measured stalagmite widths are correlated to the dispersal in the impact point position of the drop.

This article presents isotopic measurements (δ18O and δD) of precipitation and cave drip water from two sites in southern France in order to investigate the link between rainfall and seepage water, and to characterize regional rainfall isotopic variability. These data, which are among the longest series in France, come from two rainfall stations in south-west France (Le Mas 1996–2012, and Villars 1998–2012; typically under Atlantic influence), and from one station in the south-east (Orgnac 2000–2012; under both Mediterranean and Atlantic influence). Rainfall isotopic composition is compared to drip water collected under stalactites from the same sites: Villars Cave (four drip stations 1999–2012) in the south-west, and Chauvet Cave (two drip stations 2000–2012) in the south-east, near Orgnac. The study of these isotopic data sets allows the following conclusions to be drawn about the rainfall/drip water relationships and about rainfall variability: (1) the cave drip water isotopic composition does not show any significant changes since the beginning of measurements; in order to explain its isotopic signature it is necessary to integrate weighted rainfall δ18O of all months during several years, which demonstrates that, even at shallow depths (10–50 m), cave drip water is a mixture of rain water integrated over relatively long periods, which give an apparent time residence from several months to up to several years. These results have important consequences on the interpretation of proxies like speleothem fluid inclusions and tree-ring cellulose isotopic composition, which are used for paleoclimatic studies; (2) in the Villars Cave, where drip stations at two different depths were studied, lower δ18O values were observed in the lower galleries, which might be due to winter season overflows during infiltration and/or to older rain water with a different isotopic composition that reaches the lower galleries after years; (3) local precipitation is characterized by local meteoric water lines, LMWL, with δ18O/δD slopes close to 7 in both areas, and correlations between air temperature and precipitation δ18O are low at both monthly and annual scales, even with temperature weighted by the amount of precipitation; (4) the mesoscale climate model REMOiso, equipped with a water isotope module, allows the direct comparison of modeled and observed long term water isotope records. The model slightly overestimates rainfall δ18O at the respective sampling stations. However, it simulates very well not only the seasonal rainfall isotopic signal but also some intra-seasonal patterns such as a typical double-peak δ18O pattern in winter time.

In the last 150 years, some prehistoric painted caves suffered irreversible degradations due to misperception of conservation issues and subsequent mismanagement. These sites presented naturally an exceptional stability of their internal climate allowing conservation in situ of outstanding fragile remains, some for nearly 40,000 years. This is for a large part due to exchanges of air, CO2, heat and water with the karstic system in which these caves are included. We introduce the concept of underground confinement, based on the stability of the inner cave climate parameters, especially its temperature. Confined caves present the best conservative properties. It is emphasized that this confined state implies slow exchanges with the surrounding karst and that a stable cave cannot be viewed as a closed system. This is illustrated on four case studies of French caves of various confinement states evidenced by long term continuous monitoring and on strategies to improve their conservation properties. The Chauvet cave presents optimal conservation properties. It is wholly confined as shown by the stability of its internal parameters since its discovery in 1994. In Marsoulas cave, archeological works removed the entrance scree and let a strong opening situation of the decorated zone. Remediation is expected by adding a buffer structure at the entrance. In Pech Merle tourist cave, recurrent painting fading was related to natural seasonal drying of walls. Improvement of the cave closure system restored a confined state insuring optimal visibility of the paintings. In Gargas tourist cave, optimization of closures, lighting system and number of visitors, allowed it to gradually reach a semi-confined state that improved the conservation properties. Conclusions are drawn on the characterization of confinement state of caves and on the ways to improve their conservation properties by restoring their initial regulation mechanisms and to avoid threats to their stability.

The last deglaciation and its climatic events, such as the Bølling–Allerød (BA) and the Younger–Dryas (YD), have been clearly recorded in the δ13C profiles of three stalagmites from caves from Southern France to Northern Tunisia. The three δ13C records, dated by thermal ionization mass spectrometric uranium–thorium method (TIMS), show great synchroneity and similarity in shape with the Chinese cave δ18O records and with the marine tropical records, leading to the hypothesis of an in-phase (between 15.5 and 16 ka ∼±0.5 ka) postglacial warming in the Northern Hemisphere, up to at least 45°N. The BA transition appears more gradual in the speleothem records than in the Greenland records and the Allerød seems warmer than the Bølling, showing here close similarities with other marine and continental archives. A North–South gradient is observed in the BA trend: it cools in Greenland and warms in our speleothem records. Several climatic events are clearly recognizable: a cooler period at about 14 ka (Older Dryas (OD)); the Intra-Allerød Cold Period at about ∼13.3 ka; the YD cooling onset between 12.7 and 12.9±0.3 ka. Similar to the BA, the YD displays a gradual climate amelioration just after its onset at 12.75±0.25 ka, up to the Preboreal, and is punctuated by a short climatic event at 12.15 ka. Even though the Southern Hemisphere stalagmite records seem to indicate that the postglacial warming started about ∼3 ka±1.8 ka earlier in New Zealand (∼41 °S), and about ∼1 to ∼2 ka earlier in South Africa (24.1 °S), large age uncertainties, essentially due to slow growth rates, make the comparison still perilous. The overall δ13C speleothem record seems to follow a baseline temperature increase controlled by the increase in insolation and punctuated by cold events possibly due to the N-America freshwater lake discharges.

We assess the aerodynamics of the atmosphere in some limestone caves using a 5‐year monitoring of the Aven d'Orgnac system, shorter thermal vertical profiling experiments, and comparison with the time series from other French caves. In the first rooms, located under the Aven opening, our records indicate, for each year, a succession of a summer regime characterized by stable parameters (except for the perturbations introduced by tourist visits) and a winter regime, in which the inner air temperature drops and is highly correlated with that outside. Atmospheric composition suggests that during the winter regime the cave is ventilated by the outside air. We show that the onset of the winter regime is governed by a thermo‐convective instability involving the inflow of the outside cold and dense air. Atmospheric temperature and composition allow us to follow the stepwise progression of the winter regime toward the adjacent rooms.

We present temperature measurements recorded at a 15 min time step between October 2002 and April 2003 inside the La Peyrere cave (Baget karstic system, Central Pyrenees) on six 0.01 degrees C sensitivity sensors distributed on the whole recognized cave, down to a depth of 57 m. Rainy events are associated to a steep signal of a few hundredth to a few tenth of degrees in amplitude starting 1 h to one day after rain, and with a sign depending mostly of the outside temperature. The temperature signal does not correlate well with the rainfall, while the water level does with a maximum water rising rate 2.5 h after rain. The spectral density of the temperature signal displays one peak at a period of 3 days, which is also present in the rain signal and which is likely to be related to climatic parameters, and a broad smooth zone of spectral energy close to a I day period.By comparing a 'superficial' and a 'deepest' group of sensors, we note that the flood signal is more pronounced on the deepest sensor group whatever the outside temperature, and that the annual temperature variation is also larger on this sensor group. This could indicate that rain water flows in the cave through its base and explain the development in depth of the cave. Due to the arrival of water with different temperatures and mineralizations at different levels, double diffusive convection is likely to be triggered in the cave. We suggest that the onset of convection could be associated to the oscillations observed on the temperature signal at the onset of the flood. (c) 2005 Elsevier B.V. All rights reserved.

Progressive metamorphic zones developed in pelites around the Aribinda granite, Burkina Faso, indicate contact metamorphism at 5–6kbar. Biotite, chloritoid, staurolite–kyanite zones are distributed concentrically around the Aribinda pluton on its northern margin but are displaced by later thrust faults in the south of the Aribinda area and in the nearly Tampelga area. These metamorphic and structural characteristics provide new constraints for the geodynamical evolution of the Eburnean orogeny in the North part of the Baoulé-Mossi domain. They show the leading part of the granitoid emplacement in the thermic structuration of the greenstone belts and the post-metamorphic character of the tangential tectonic. In Burkina Faso, the Eburnean orogeny underwent: (1) initial greenschist-facies metamorphism; (2) emplacement of granitoids at mid- deep-crustal levels leading to unusual medium pressure metamorphism; (3) later thrusting.

A survey of CO2 concentrations in the atmosphere of the Aven d'Orgnac shows that aerodynamic transfer can be a major process in karst system dynamics. The local meteorological conditions and the geometry of the cavity govern exchanges between the cave atmosphere and the exterior. Air enriched with biogenic CO2 is transferred through the microfissural network by diphasic infiltration from soil to caves where it is continuously produced from rock walls. Analysis of the aerodynamic emptying of confined zones and direct flow measurement give a mean CO2 production per surface unit of the cave rock wall. (C) 2001 Academie des sciences / Editions scientifiques et medicates Elsevier SAS.

Painted caves are karstic cavities here considered as stable physical systems in a state of dynamic equilibrium. From the example of the Gargas cave, we show that introduction of excess energy (visitors, lighting) causes a loss of stability and introduces a risk of degradation in the cavity. From different approaches, we identify the periods and the causes of instability and we determine the maximum level of introduced energy which would preserve the conservative properties of the cavity. These results allow cave equipment and visitor capacity compatible with satisfactory conservation conditions to be defined. ((C) Academie des sciences / Elsevier, Paris.).

The Guibare and Fete Kole deposits in Burkina Faso consist of Birimian gold-bearing quarts and tourmaline veins in metamorphosed volcano-sedimentary formations of an Early Proterozoic greenstone belt, Tourmaline compositions for the two prospects vary according to occurrence: dravite in the Guibare deposit. hosted by metabasic to meta-ultrabasic rocks, in contrast to schorl in the Fete Role deposit. hosted by metasedimentary and metavolcanic rocks. The major control on tourmaline composition thus seems to be the Mg/(Mg + Fe) value of the host rock rather than the composition of the hydrothermal fluid. In both deposits, the gold is not associated with sulfides, bur rather is concentrated within tourmaline layers, typically at the tips of the tourmaline crystals and as small grains filling fractures in tourmaline. Mossbauer and infrared spectroscopic data show the presence of ferric iron coupled with evidence of deprotonation in these tourmalines, indicating a relatively oxidizing environment for the Au deposits. A drop of fluid pressure and deprotonation could have induced physicochemical changes that caused deposition of the gold.

The Loraboue prospect is located in the northern part of the Poura district, in the Boromo greenstone belt (Burkina Faso). Gold mineralization occurs in albitized rock (albitite) and carbonatized ultrabasic rock (listvenite), which represents a new type of ore deposit in Burkina Faso. The precipitation of gold can be achieved during the late stage of alteration inducing the crystallization of ankerite, quartz and muscovite in albitite, and ferroan-magnesite, fuchsite and quartz in serpentinized uitramafic rocks. Gold deposition Is linked to the formation of sulfides (mainly pyrite associated with quartz), itself controlled by the Fe/(Fe + Mg) ratio of the initial host-rock. This could explain the higher Au contents of albitite (0.5 <Fe/(Fe + Mg) < 0.9 ; 5 to 1250 ppb Au) than hydrothermalized ultrabasic rock (0.1 < Fe/(Fe + Mg) < 0.2; 10 to 200 ppb An). These unusual rocks could represent an attractive target for Au prospecting in the Burkina Faso.

The Taparko gold deposit, located in the eastern branch of the Proterozoic Birimian Bouroum-Yalogo greenstone belt (Burkina Faso) consists of a network of quartz veins developed in a N 170° trending shear zone (250 m wide, 4 km long) superimposed on the regional Birimian structural pattern. The quartz vein network is composed of: (a) a dominant array of quartz veins (type 1), parallel to the shear zone and comprising strongly deformed dark quartz exhibiting foliation, layering, ribbon, tension gashes, etc.; (b) oblique and subparallel related veins (type 2) of gray to white weakly deformed quartz crosscutting the dominant quartz veins resulting in breccia structures; and (c) shallow dipping veins (type 3), cross-cutting veins types 1 and 2 and filled by undeformed white buck structure quartz. Cross-cutting relationships and different quartz types in different veins and within individual veins imply a concomitant filling of the veins during the progressive deformation. Initial sinistral transcurrent shearing evolved with time to sinistral reverse shearing. Metallic minerals occur only in type 1 and 2 veins and were deposited in two stages, with native gold being related to second stage sulfides. Gold (and chalcopyrite) precipitated preferentially upon the surfaces of fractured pyrite grains in low-pressure sites (pressure shadow zones) around and/or within the sulfide grains (along subsequently annealed fractures). The formation of the South Taparko deposit can be divided into a succession of events: (a) during the first event, N 170°-directed sinistral transcurrent shearing resulted in a N 20° mylonitic foliation and fractured rock which allowed H2O-, CO2- and SiO2-rich fluids to circulate and deposit quartz with buck texture; (b) during the second event, type 1 quartz was strongly deformed and type 2 veins formed with sigmoidal shapes as viewed on a horizontal plane; and (c) during the third event, the sinistral transcurrent shearing evolved to sinistral reverse shearing and the deformation style evolved correspondingly from ductile to brittle-ductile. During the last phase of deformation gold nucleated and deposited in low-pressure zones.

A new occurrence of a Au ore deposit (Larafella prospect, Poura district) is defined within lenses of albitites (5-8 m thick) interbedded with metasediments and metavolcanites of the Birimian greenstone belts of Burkina Faso (West Africa). Albitites have an homogeneous chemical composition close to albite and a well-developed microgranular texture. In contrast to the highly strained enclosing host metavolcanic formations, which possess a strong penetrative cleavage, the unfoliated albitite lenses exhibit only brittle structures, which are essentially tensional gashes filled by quartz and calcite fibres, unorientated euhedral albite crystals, quartz and calcite crystals and geared quartz crystals.The strict delineation of the Au anomaly within the albitic lenses, together with the temporal relationships between Au precipitation and tensional gashes, suggest that albitites - due to their high viscosity and their brittle behaviour - constitute a potential reservoir for the concentration of CO2, S, H2O, As and Au fluids. (C) 1997 Elsevier Science Limited.

Field observations, structural measurements and anisotropy of magnetic susceptibility measurements have contributed to define the main features of a granite massif which was emplaced late within the Eburnean magmatic complex of the Lower Proterozoic of West Africa. It is concluded that the magma infilled a gash in the brittle crust. This opening in the crust possibly formed as a jog along a sinistrally offset NE-SW fracture, one of many that affect the Birimian basement of eastern Burkina Faso.

A lateritic profile, developed in the area of the Gangaol gold mineralization, underwent intensive weathering episodes resulting in significant dissolution of the most resistant heavy minerals including gold and zircon. In the upper horizon of the ironcrust, those weathered minerals coexist with unweathered gold particles characterized by primary shapes and fresh sulfides. Within this horizon, the matrix is richer in gold particles than in indurated ferruginous nodules. These observations suggest this part of the ironcrust is constituted by elements of varing compositions with varing degrees of weathering. The lack of gold particles in the medium part of the profile confirms the allochthonous character of the parent material of the upper part of the ironcrust.

In the quartz veins emplaced within the Birimian series, native gold (10 to 14% Ag) was deposited during gradual deformation in the low pressure zones (tension gashes cross-cutting the quartz foliation, pressure shadow zones and tension gashes of the pyrite). Later, partially remobilized by supergene fluids, the gold recrystallizes with a dendritic habitus. Dendrites are supported by crystallized euhedral after-quartz.

The transcurrent tectonics in the Djibo area is characterized by sub-meridian sinistral ductile shear zones. The characteristics of the deformation affecting the shear zones in low-grade metamorphic conditions are defined This major tectonic event is known in throughout West Africa and corresponds to the Eburnean orogeny.

The influence of electron beam irradiation on migrational behaviour of additives present in food packaging material was studied. The migration experiments were carried out on irradiated and non-irradiated polypropylene pouches containing aqueous food simulating liquids (FSL) for 10 days at 40-degrees-C. The controls were irradiated and non-irradiated pouches without FSL contact. After the contact period, the polypropylene and the FSL were analysed. A comparison between the results obtained by the two analyses showed the migration of three products of antioxidant degradation from the polypropylene into the FSL, and a partial decomposition of these migrants in the FSL.

The long-term influence of electron beam irradiation on food packaging materials (OPP) was studied. After irradiating the material at dose levels of 2, 5 and 10 kGy, we have shown a partial or complete disappearance of the antioxidant (Irganox 1010 and Irgafos 168) over time and a release of five new compounds resulting from antioxidant degradation. All of these degradation compounds have been identified and quantitatively analysed in relation to post-irradiation time and absorbed dose. These results allow an explanation of the antioxidants' behaviour during storage of the irradiated polypropylene at room temperature.