The Australian-Antarctic segment of Gondwana

Australia is one of the major continental terranes in Gondwana’s structure. At the same time, the precise position of Australia in this structure has not yet been clearly identified. According to different works, Australia is connected to Antarctica in a number of areas near Wilkes Land, Adelie Land, and Victoria Land. The comprehensive analysis of the geological and geophysical data allows us to reconstruct the optimal relative position of the continents and to reach a conclusion about the propagation of the tectonic structures of Australia towards Antarctica.     

Kinematic Model of Development of Eastern Areas of the Gakkel Mid-Ocean Ridge in the Eurasian Basin of the Arctic Ocean

Oceanology - A new map of the axes of linear magnetic anomalies for eastern regions of the Eurasian Basin has been compiled. Based on the results of Russian geomagnetic surveys, paleoanomaly C25...     

Studies and characterizations of the Al Zarnkh meteorite

Abstract— A newly fallen Sudanese meteorite named Al Zarnkh was investigated using room and liquid nitrogen temperature Mössbauer measurements, X‐ray diffraction (XRD), and electron probe microanalysis (EPMA) in conjunction with energy dispersive X‐ray microscopy. The Mössbauer spectra exhibited strong paramagnetic doublets with magnetic sextets. The doublets are assigned to olivine and pyroxene, while the magnetic sextets are assigned to troilite and kamacite. Based on microprobe analyses and textural studies, olivine is the most abundant phase and occurs as fine to medium grained laths both in the groundmass and in barred olivine chondrules. Both orthopyroxenes and clinopyroxenes are present and these tend to be granular. Plagioclase is an abundant interstitial groundmass phase. Chromites were detected in some groundmass olivine and are highly chromiumand iron‐rich with no Fe³⁺ detected. The kamacite contains small amounts of Co. The mole fraction of the Fe end‐member of olivine (fayalite) and orthopyroxene (ferrosilite) are found to be about 28% and 23%, respectively. These values are compared with that obtained from two chondritic meteorites. Based on these results, the studied meteorite is classified as an ordinary LL5 chondrite.     

Découverte de niveaux phosphatés associés à des restes de vertébrés dans les dépôts carbonatés du Coniacien–Santonien du Jabal Abtar : épisode précoce de la phosphatogenèse sénonienne des Palmyrides (Syrie centrale)

Sedimentologic study of carbonated sediments of the Rmah-I member (Coniacian–Santonian) of Jabal Abtar, central southern Palmyrides (Central Syria), uncovers phosphatic levels, associated with marine vertebrate remains, that give evidence of an early episode of the Senonian phosphatogenesis in the Palmyrides. Sedimentary sequence analysis reveals a gradual marine transgression during the Senonian. Phosphatic sedimentation occurred in a shallow neritic marine environment almost connected with the open sea. Condensed sedimentation could have contributed to the phosphatogenesis. To cite this article: A.K. Al Maleh, N. Bardet, C. R. Geoscience 335 (2003).     

Model atmosphere parameters of the binary systems COU1289 and COU1291

The spectral energy distributions between λ 3700 Å and λ 8100 Å of the binary systems COU1289 and COU1291 have been measured with the Carl‐Zeiss‐Jena 1 m telescope of the Special Astrophysical Observatory. Their B, V, R magnitudes and B – V colour indices were computed and compared with earlier investigations. Model atmospheres of both systems were constructed using a grid of Kurucz blanketed models, their spectral energy distributions in the continuous spectrum were computed and compared with the observational ones. The model atmosphere parameters for the components of COU1289 were derived as: T ^a_eff = 7100 K, T ^b_eff = 6300 K, log g _a = 4.22, log g _b = 4.22, R _a = 1.50 R_⊙, R _b = 1.40 R_⊙, and for the components of COU1291 as: T ^a_eff = 6400 K, T ^b_eff = 6100 K, log g _a = 4.20, log g _b = 4.35, R _a = 1.47 R_⊙, R _b = 1.12 R_⊙. The spectral types of both components of the system COU1289 were concluded as F1 and F7, and of the system COU1291 as F6 and F9. Finally the formation and evolution of the systems were discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Long-term fluid circulation in extensional faults in the central Catalan Coastal Ranges: P–T constraints from neoformed chlorite and K-white mica

The neoformation of chlorite and K-white mica in fault rocks from two main faults of the central Catalan Coastal Ranges, the Vallès and the Hospital faults, has allowed us to constrain the P–T conditions during fault evolution using thermodynamic modeling. Crystallization of M1 and M2 muscovite and microcline occured as result of deuteric alteration during the exhumation of the pluton (290 °C > T > 370 °C) in the Permian. After that, three tectonic events have been distinguished. The first tectonic event, attributed to the Mesozoic rifting, is characterized by precipitation of M3 and M4 phengite together with chlorite and calcite C1 at temperatures between 190 and 310 °C. The second tectonic event attributed to the Paleogene compression has only been identified in the Hospital fault with precipitation of low-temperature calcite C2. The shortcut produced during inversion of the Vallès fault was probably the responsible for the lack of neoformed minerals within this fault. Finally, the third tectonic event, which is related to the Neogene extension, is characterized in the Vallès fault by a new generation of chlorite, associated with calcite C4 and laumontite, formed at temperatures between 125 and 190 °C in the absence of K-white mica. Differently, the Hospital fault is characterized by the precipitation of calcite C3 during the syn-rift stage at temperatures around 150 °C and by low-temperature fluids precipitating calcites C5, C6 and PC1 during the post-rift stage. During the two extensional events (Mesozoic and Neogene), faults acted as conduits for hot fluids producing anomalous high geothermal gradients (50 °C/km minimum).     

New system for the assessment of annual groundwater recharge from rainfall in the United Arab Emirates

In this study, the first groundwater recharge map for United Arab Emirates (UAE) was developed using the recharge potential and water table fluctuation methods. Recharge potential estimates were made using information about infiltration rate, soil type, ground slope, geological and hydrogeological factors, and the availability of rainfall harvesting infrastructure and were validated by measurements of water table rise in alluvial aquifers in wadis. Based on this information, the total recharge in the UAE is estimated to be about 133 million cubic meters per year (MCM/year). Annual recharge rates are calculated to vary between 1 and 28% of precipitation in the different regions of UAE depending on several natural and manmade parameters including, among others, recharge enhancing infrastructure. Estimates from the two methods are 98% in agreement; which suggests that the recharge potential method is suitable for estimating aquifer’s recharge in UAE and arid regions. The water table fluctuation method was found to be more suitable for assessing recharge through gravel plains and wadis in mountainous areas.