Textural and structural evidences for cumulative processes and layering in Svidnya Pluton, Stara Planina Mountain, Bulgaria.

International audienc

Comparative mineralogical study of mafic minerals from Variscan potassic-alkaline rocks in Stara Planina Mountains, Bulgaria

International audienc

Segregation of olivine grains in volcanic sands in Iceland and implications for Mars

International audienceBasaltic sands cover several plains in volcanic regions on Earth and dominate the aeolian sediments on Mars but basaltic sands are not as well characterized as felsic sands. The Lambahraun sandy-lava plain in Iceland was chosen as a martian analog to study the physical sorting of basaltic sands. The strong winds affecting the plain and its young age (<4000 yr) have preserved unaltered sand grains. Sands displayed subtle differences in bulk chemical composition from the basaltic source rocks suggesting that mineral abundances are modified by the aeolian transport. A paired enrichment in Mg and Ni in sands relative to the source rock is observed and results from a higher proportion of olivine grains in sand. This enrichment is variable among sand samples and is correlated with the decrease of the mean grain size of sand; a value related to the degree of aeolian sorting. This enrichment is explained by the presence of well-developed olivine minerals (100 to 500 pm in length) in the source rocks, olivine hardness and density, and the removal of plagioclases. As olivine has been detected by spectral data in several sand dunes on Mars, these results have important implications for martian studies. It shows that olivine abundances deduced from spectral data on martian sand dunes could overestimate that of the source rocks, whereas the presence of a few percents of olivine in the rocks can cause olivine enrichment by aeolian processes. In general, our results show that mineral segregation in basaltic sands should be considered when mineralogical and chemical data of the Mars surface are interpreted. (C) 2011 Elsevier B.V. All rights reserved

Segregation Of Olivine Grains In Volcanic Sands In Iceland - Implications For Mars

Poster n° 200

Lake Burdur and its area from last 2000 years : sedimentary record of climate and environmental evolution

International audienc

Mineralogy of recent volcanic plains in the Tharsis region, Mars, and implications for platy-ridged flow composition.

International audienceVolcanism on Mars occurred until recently, but the mineralogy of recent lava plains is poorly known because few regions display fresh outcrops devoid of dust. Using visible and near infrared data of the Mars Express probe, two new volcanic plains in Noctis Labyrinthus have been identified, and the existence of a volcanic plain on the floor of Echus Chasma has been confirmed. Crater retention ages estimated for these three plains range between 50 and 100 My, corresponding to the Late Amazonian. These plains represent an excellent opportunity to constrain the mineralogy of recent volcanic rocks. Results show that basaltic compositions with plagioclase and high calcium pyroxene are predominant. The low olivine proportion suggests that the apparent fluidity of these flat plains is not related to magmas being ultramafic. In addition, a platy-ridged texture is observed in two of the studied regions. Our study shows, for the first time, that this texture is associated with volcanic rocks, and that these rocks are of typical basaltic mineralogy. Finally, these volcanic plains are located more than 1000 km east of previously known late Amazonian volcanic centers of the Tharsis region, an observation to be taken into account when considering models of recent volcanism on Mars. (C) 2009 Elsevier BM. All rights reserved

Mineralogy of recent volcanic plains in the Tharsis region, Mars, and implications for platy-ridged flow composition.

International audienceVolcanism on Mars occurred until recently, but the mineralogy of recent lava plains is poorly known because few regions display fresh outcrops devoid of dust. Using visible and near infrared data of the Mars Express probe, two new volcanic plains in Noctis Labyrinthus have been identified, and the existence of a volcanic plain on the floor of Echus Chasma has been confirmed. Crater retention ages estimated for these three plains range between 50 and 100 My, corresponding to the Late Amazonian. These plains represent an excellent opportunity to constrain the mineralogy of recent volcanic rocks. Results show that basaltic compositions with plagioclase and high calcium pyroxene are predominant. The low olivine proportion suggests that the apparent fluidity of these flat plains is not related to magmas being ultramafic. In addition, a platy-ridged texture is observed in two of the studied regions. Our study shows, for the first time, that this texture is associated with volcanic rocks, and that these rocks are of typical basaltic mineralogy. Finally, these volcanic plains are located more than 1000 km east of previously known late Amazonian volcanic centers of the Tharsis region, an observation to be taken into account when considering models of recent volcanism on Mars. (C) 2009 Elsevier BM. All rights reserved