Families of double symmetric “Schubart-like” periodic orbits

We consider a class of Hamiltonian systems with two degrees of freedom with singularities. This class includes several symmetric subproblems of the $n$ -body problem where the singularities are due to collisions involving two or more bodies. “Schubart-like” periodic orbits having two collisions in one period, are present in most of these subproblems. The purpose of this paper is to study the existence of families of such a periodic orbits in a general setting. The blow up techniques of total collision and infinity are applied to our class of Hamiltonian system. This allows us to derive sufficient conditions to ensure the existence of families of double symmetric “Schubart-like” periodic orbits having many singularities. The orbits in the family can be parametrized by the number of singularities in one period. The results are applied to some subproblems of the gravitational $n$ -body problem.     

Imaging Spectroscopy of a White-Light Solar Flare

We report observations of a white-light solar flare (SOL2010-06-12T00:57, M2.0) observed by the Helioseismic Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The HMI data give us the first space-based high-resolution imaging spectroscopy of a white-light flare, including continuum, Doppler, and magnetic signatures for the photospheric Fe i line at 6173.34 Å and its neighboring continuum. In the impulsive phase of the flare, a bright white-light kernel appears in each of the two magnetic footpoints. When the flare occurred, the spectral coverage of the HMI filtergrams (six equidistant samples spanning ±172 mÅ around nominal line center) encompassed the line core and the blue continuum sufficiently far from the core to eliminate significant Doppler crosstalk in the latter, which is otherwise a possibility for the extreme conditions in a white-light flare. RHESSI obtained complete hard X-ray and γ-ray spectra (this was the first γ-ray flare of Cycle 24). The Fe i line appears to be shifted to the blue during the flare but does not go into emission; the contrast is nearly constant across the line profile. We did not detect a seismic wave from this event. The HMI data suggest stepwise changes of the line-of-sight magnetic field in the white-light footpoints.     

Geochemical characteristics of the high- and low-Ti basaltic rocks from the uplifted shoulder of the Ohře (Eger) Rift,Western Bohemia

High-Ti melanephelinite (3.8–5.9 wt% TiO₂), medium-Ti (phono)tephrite (2.7–3.1 wt% TiO₂), and low-Ti olivine melanephelinite/basanite (1.9–2.3 wt.% TiO₂) are subordinate rock types in the central European Cenozoic Volcanic Province. A contrasting melanephelinite to (phono)tephrite series occurs in the Lou?ná–Oberwiesenthal Volcanic Centre (37–28 Ma) and also as satellite volcanic bodies (26–12 Ma) together with olivine melanephelinite/basanite (17–20 Ma) on the southwestern periphery of the Kru?né hory mountains (Erzgebirge). The volcanic rocks intrude the Variscan basement of the uplifted shoulder of the Oh?e/Eger Rift in the Kru?né hory mountains of the Bohemian Massif. Low Mg# (44–59) and Cr, Ni contents and enrichment of LILE, Zr, Hf, Nb, Ta, U, Th and LREE in the high-Ti melanephelinites contrast with the composition of primitive low-Ti olivine melanephelinites/basanites displaying high Mg# (63–74) and high contents of compatible elements. The high-Ti melanephelinites reveal a wide range in initial ⁸⁷Sr/⁸⁶Sr of ca. 0.7034–0.7038 and ε_Nd of 2.4–4.9. The low-Ti melanephelinites show an overlapping range of initial ⁸⁷Sr/⁸⁶Sr of ca. 0.7035–0.7036 and ε_Nd of 4.3–5.5. The large variation in initial ⁸⁷Sr/⁸⁶Sr ratios at similar ε_Nd values in those rock types is interpreted as evidence for melting of metasomatized lithospheric mantle sources comprising K-bearing phases with radiogenic Sr. Modification of the olivine-free alkali basaltic magmas by differentiation or crustal contamination could give rise to the medium-Ti (phono) tephrites. The initial isotope ratios of all samples are consistent with HIMU-mantle sources and contributions from lithospheric mantle. The olivine-free melanephelinitic rocks often contain alkali pyroxenite–ijolite xenoliths with initial ⁸⁷Sr/⁸⁶Sr ratios of ca. 0.7036 and ε_Nd of 3.0. We interpret these xenoliths as samples of an intra-crustal alkali complex derived from similar mantle sources as those for the basaltic volcanic rocks.     

Magmatic erosion of the solidification front during reintrusion: the eastern margin of the Tuolumne batholith, Sierra Nevada, California

The Tuolumne batholith, Sierra Nevada, California, consists of several nested granitoid units and is an example of upper-crustal normally zoned intrusions. The two outermost units of the batholith are separated by a wide gradational contact in what is interpreted to represent a large magma chamber. In the Potter Point area near the eastern margin of the batholith, the gradational contact is cross-cut by a network of interconnected mafic–felsic sheets, which grade into zones of magmatic erosion by stoping where the host granodiorite between the sheets was entirely removed and replaced by younger enclave-rich quartz diorite. We interpret these features to record disruption of a steep solidification front, which migrated inwards from the eastern batholith margin and separated the mushy to solidified margin from the remaining active magma chamber. When intersecting the gradational contact, the solidification front started to break up via a network of tectonically driven fractures accompanied by simultaneous injection of localized magma pulses. The solidification front break-up is interpreted here as an initial stage of a “recycling” process, whereby older magma mush is disrupted and incorporated into younger magma batches, a process we propose to have been widespread along internal contacts in the Tuolumne magma chamber.     

Hydrogeochemistry of abandoned Pb sulphide mines: the mining district of La Carolina (southern Spain)

The impact of past mining activities on the quality of groundwater and surface water has been investigated in the mining district of La Carolina (southern Spain, province of Jaén), a region characterised by the presence of mineralisations of Pb–Ag, Cu and Fe sulphides and Ba sulphates. The chemistry of waters from flooded galleries, shafts and drainage adits has been compared with that of surface waters in the same area. Generally, waters present neutral pH, since carbonates neutralise the acidity produced by the oxidation of Fe-bearing sulphide minerals in the mine impacted water. Despite of this natural attenuation process, in most of the cases, the mine groundwater is of low quality and shows high dissolved SO₄ (up to 3.7 g/l), Fe and Mn contents (tens to hundreds mg/l), exceeding the limit established by the guidelines of the World Health Organization for drinking water. Generally, the surface waters are of the sulphate calcium–magnesium to magnesium types, with moderate mineralisation. Post-rebound mine waters caused degradation of receiving watercourses in which the Fe contents are usually high, with values close to 3 g/l, and the mineralisation is greater as the channels run down in the mining zone. During dry seasons a considerable increase of salts and metals dissolved in stream waters was found, due to the decreasing contributions by run-off in this semiarid region, whereas the abandoned mine discharges remained practically constant.     

Paleoshoreline reconstruction: A proposed method to approach submerged prehistoric landscapes of Espiritu Santo Island,Baja California Sur,Mexico

When the first Americans inhabited the area now known as Isla Espiritu Santo, around 12.5 and 6 ka, the sea level continuously rose. This resulted in the loss of the coastal territory and the retreat of the human population further inland. Part of the archaeological evidence of this period currently lies over the seafloor and under the seabed. Therefore, reconstructing paleoshorelines is a necessary first step toward submerged precontact archaeology and a broad understanding of the spatial context in which those human populations interacted and how the landscapes changed. Isla Espiritu Santo is of prehistoric importance as it contains numerous Paleocoastal tradition sites as early as ~12,400 Cal B.P. This research aims to reconstruct the changing shoreline positions as sea levels rose around Isla Espiritu Santo between 12.5 and 6.5 ka. We apply numerical modeling to map digital elevation models at 1 ka intervals by estimating the changes in the morphology of the seafloor according to the deposition rates and global sea-level curve. The results show the evolution of coastal morphology and paleoshoreline's position. Three primary geoforms are proposed: (1) coastal plains, (2) tombolo, and (3) a coastal lagoon–island barrier system. This also offers insights into the physical aspect of submerged prehistoric landscapes and the possible resource exploitation options of early societies. In this research, the reconstruction of submerged landscapes seeks to contribute to the long-term goal of locating submerged precontact sites.