5,978 research outputs found
Contour spectrograms for POGO analysis
Contour spectrograms for POGO analysis in Saturn S-2 and S-4b stage
Revision of Scheumann’s classification of melilitic lamprophyres and related melilitic rocks in light of new analytical data
Dykes of the Late Cretaceous to Early Tertiary (79.5 ± 3.5 to 60.7 ± 2.4 Ma) melilitic rock series of the Osečná Com-
plex and the Devil’s Walls dyke swarm, including ultramafic lamprophyres – polzenites – of Scheumann (1913) occur
dispersed in the entire Upper Ploučnice River basin in northern Bohemia.
Polzenites and associated melilitic rocks are characterized by the mineral association of olivine + melilite ± nephe-
line, haüyne, monticellite, phlogopite, calcite, perovskite, spinels and apatite. New data on their mineral and chemical
compositions from original Scheumann’s localities (the Vesec, Modlibohov, Luhov types) argue against the abolition
of the group of ultramafic lamprophyres and the terms ‘polzenite’ and ‘alnöite’ by the Le Maitre (2002) classification.
Marginal facies and numerous flat apophyses of the lopolith-like body known as the Osečná Complex show an olivine
micro-melilitolite composition (lamprophyric facies). The porphyritic texture, chemical composition and the presence of
characteristic minerals such as monticellite and phlogopite point to their affinity with ultramafic lamprophyres – polze-
nites of the Vesec type. Melilite-bearing olivine nephelinites to olivine melilitites (olivine + clinopyroxene + nepheline
+ melilite ± haüyne and spinels with apatite) form a swarm of subparallel dykes known as the Devil’s Walls.
The Scheumann’s non-melilite dyke rock “wesselite”, spatially associated with polzenites and often erroneously attributed
to the polzenite group, is an alkaline lamprophyre of monchiquite to camptonite composition (kaersutite + phlogopite
+ diopside + olivine phenocrysts in groundmass containing clinopyroxene, phlogopite, haüyne, analcime, titanian mag-
netite, apatite ± glass/plagioclase). First K–Ar data show Oligocene ages (30.9 ± 1.2 to 27.8 ± 1.1 Ma) and an affinity to
the common tephrite–basanite rock series
Dark Matter and Dark Radiation
We explore the feasibility and astrophysical consequences of a new long-range
U(1) gauge field ("dark electromagnetism") that couples only to dark matter,
not to the Standard Model. The dark matter consists of an equal number of
positive and negative charges under the new force, but annihilations are
suppressed if the dark matter mass is sufficiently high and the dark
fine-structure constant is sufficiently small. The correct relic
abundance can be obtained if the dark matter also couples to the conventional
weak interactions, and we verify that this is consistent with particle-physics
constraints. The primary limit on comes from the demand that the
dark matter be effectively collisionless in galactic dynamics, which implies
for TeV-scale dark matter. These values are
easily compatible with constraints from structure formation and primordial
nucleosynthesis. We raise the prospect of interesting new plasma effects in
dark matter dynamics, which remain to be explored.Comment: 14 pages, 6 figures Updated equations and figure
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