Numerical simulation of the origin of red sandstone and Cu accumulation in pore solutions

Interaction of igneous rocks with river (rain) water in the systems granite-water, basalt-water, and dunite-water open with respect to carbon dioxide (PCO₂ = 10^?4, 10^?3, and 10^?2 bar) and oxygen (PO₂ from 10^?81 to 10^?1 bar) is numerically simulated at 25 and 50°C and a mass ratio of water and rock R/W ≤ 10. Equilibrium simulations indicate that, first, the differences in the mineralogical composition of the transformation products of the igneous rocks are insignificant, and second, Cu extraction from minerals of the rocks is optimal at Eh from +200 to ?100 mV. Simulations of the systems with regard for the dissolution rates of minerals indicate that the chemical weathering time of the rocks is few hundred thousands years.     

Application of Spectroscopic Diagnostics to Early Observations with the SOHO Coronal Diagnostic Spectrometer

The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal the determination of the physical parameters of the solar plasma using spectroscopic diagnostic techniques. Absolute intensities and intensity ratios of the EUV spectral emission lines can be used to obtain information on the electron density and temperature structure, element abundances, and dynamic nature of different features in the solar atmosphere. To ensure that these techniques are accurate it is necessary to interface solar analysis programs with the best available atomic data calculations. Progress is reported on this work in relation to CDS observations.     

Reply to ‘Comment on “The beginnings of hydrous mantle wedge melting” by Till et al.’ by Green, Rosenthal and Kovacs

The comment of Green et al. debates the interpretation of the temperature of the H₂O-saturated peridotite solidus and presence of silicate melt in the experiments of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) at <1,000?°C. The criticisms presented in their comment do not invalidate any of the most compelling observations of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) as discussed in the following response, including the changing minor element and Mg# composition of the solid phases with increasing temperature in our experiments with 14.5?wt% H₂O at 3.2?GPa, as well as the results of our chlorite peridotite melting experiments with 0.7?wt% H₂O. The point remains that Till et al. (Contrib Mineral Petrol 163:669–688, 2012) present data that call into question the H₂O-saturated peridotite solidus temperature preferred by Green (Tectonophysics 13(1–4):47–71, 1972; Earth Planet Sci Lett 19(1):37–53, 1973; Can Miner 14:255–268, 1976); Millhollen et al. (J Geol 82(5):575–587, 1974); Mengel and Green (Stability of amphibole and phlogopite in metasomatized peridotite under water-saturated and water-undersaturated conditions, Geological Society of Australia Special Publication, Blackwell, pp 571-581, 1989); Wallace and Green (Mineral Petrol 44:1–19, 1991) and Green et al. (Nature 467(7314):448–451, 2010).     

New insights into the size and timing of the Lawn Hill impact structure: relationship to the Century Zn – Pb deposit

The Lawn Hill circular structure in northwest Queensland contains unambiguous evidence of an extraterrestrial impact, including planar deformation features in quartz, impact diamonds, widespread shatter cone formation and impact melt breccia in the Mesoproterozoic basement. The question of its relevance to ore genesis is investigated because the world-class Century Zn – Pb deposit is situated at the conjunction of the 100+ km Termite Range Fault and the previously defined margin of the impact structure. The impact structure is considered to be a 19.5 km wide feature, this constrained in part by the outer margin of an annulus of brecciated and highly contorted limestone. New evidence is presented indicating impact into this Cambrian limestone, including: (i) ‘dykes’ of brecciated Cambrian limestone extending hundreds of metres into the Mesoproterozoic basement; (ii) highly contorted bedding in the limestone annulus compared with essentially undeformed limestone away from the impact site; as well as (iii) a 1 Mt megaclast of Mesoproterozoic Century-like ore suspended in the limestone. Through aerial photograph analysis, large-scale convoluted flow structures within the limestone are identified, and these are interpreted to indicate that parts of the Cambrian sequence may have been soft or only semi-consolidated at the time of impact. This highly contorted limestone bedding is suggested to represent slump-filling of an annular trough in response to impact-induced partial liquefaction of a sediment veneer. The age of impact is therefore considered to be concurrent with limestone formation during the Ordian to early Templetonian, at 520 – 510 Ma. Formation of the Century deposit is found to be unrelated to impact-generated hydrothermal activity, although some minor hydrothermal remobilisation of metals occurred. However, there was macro-scale remobilisation of gigantic ore fragments driven by impact-induced lateral and vertical injection of limestone into the Proterozoic sediments. The limestone-filled annular trough surrounds a 7.8 km diameter central uplift, consistent with formation of a complex crater morphology.     

Regional distribution of white K-mica polymorphs and their phengite content in the Central Alps

Some 150 white K-micas from the Central Alps were analysed for their polymorph and phengite content. Pre-Alpine white K-micas and those belonging to the Meso-Alpine Lepontine Metamorphic “High” show exclusively the 2M₁ polymorph. The 3T structural form, on the other hand, has been found in one third of the white K-micas formed during the Alpine regional metamorphism. In most cases this trigonal structure coexists with varying amounts of the 2M₁ form. The 3T distribution pattern suggests that this polymorph originated during the Eo-Alpine high-pressure/“low temperature” metamorphism. Provided this interpretation is correct, the sporadic occurrence of this polymorph within the Meso-Alpine staurolite zone may be used as a tracer for the Eo-Alpine metamorphism. The following improved correlation between the (060, 331) reflections of 2M₁ white K-micas and the RM-content (= 2Fe₂O₃+FeO+MgO in molar proportions), based on 24 micas from granitoid rocks, is presented: d(060, 331)= 1.498+0.082 RM. The phengite content of Alpine white K-micas belonging to the assemblage muscovite-biotite-K-feldspar-quartz was estimated from RM values or derived from chemical analyses and was found to be clearly related to metamorphic grade. Phengite-rich micas were formed during the Eo-Alpine high-P/“ low-T” metamorphism while aluminous muscovite was found within the Meso-Alpine thermal high of the Lepontine gneiss area. White K-micas from areas which underwent both the Eo-Alpine and the Meso-Alpine metamorphism display variable phengite contents. Although these micas show Tertiary Rb-Sr and K-Ar ages, the variable phengite content presumably reflects conditions during the Eo-Alpine high-P/“low-T” metamorphism. This interpretation implies that the cations occupying the interlayer positions are more easily equilibrated than those in octahedral and tetrahedral structural sites. A compilation of 3T white K-mica occurrences described in the literature is given in the appendix.     

Gas exchange between Baikal and the atmosphere during under-ice period

In the under-ice period, gas exchange between Baikal and the atmosphere is taking place through a system of coastal and perennial fractures and airholes in the ice, as well as through the surface of the ice-free part of the lake at the Angara source [24]. The total area of the open water never exceeds 0.03% of lake water area. The emission of CO₂ in the course of ice sublimation over the entire period is ≤0.02 g CO₂ from 1 m². The transport of dissolved gases from under-ice water into the atmosphere is limited by molecular diffusion in microfractions of ice cover. The narrow daily variations of CO₂ in the air in lake coastal zone is due to the effect of populated localities on its coast and large coniferous forests, which serve as diffuse sources of CO₂, as well as diurnal variations of the direction and velocity of air mass transport by local winds.     

Characteristics of the Energetic Electron Precipitation and Magnetospheric Conditions in 1994

The problem of the rapid depletion and saturation of the Earth’s outer radiation belt with energetic electrons is one of the central problems in the physics of the magnetosphere. The precipitation into the atmosphere and the escape of electrons from the magnetosphere are competing reasons for the depletion of the radiation belt. Long-term measurements of energetic electron precipitation (EEP) in the atmosphere in the experiment of the Lebedev Physical Institute (LPI) can be used to study the relative role of these phenomena. High fluence values of relativistic electrons in the outer belt is a necessary condition for EEP observation; however, the relation of the EEP rate to the condition of the belt is ambiguous, which is shown by the example of observations in 1994.     

CU Eridani — A suspected variable

Photometric observations of CU Eridani, recently classified as non-variable, indicate it to be a variable star.