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51.
Mineralogical and chemical variations in hypogene and supergene kaolin deposits in a mobile fold belt the Central Andes of northwestern Peru 总被引:1,自引:0,他引:1
In western Peru kaolin-alunite deposits occur in Lower Cretaceous and Tertiary clastic, volcaniclastic and volcanic, mostly
rhyolitic, rocks. Alunites from␣hypogene kaolin deposits yield K /Ar ages of 11.5 ±␣0.7␣Ma and 13.3 ± 0.4 Ma. In addition
to kaolin and alunite, the following minerals are present: white mica, smectite, barite, pyrophyllite, tridymite, cristobalite,
α- and β-quartz, chamosite, gibbsite, and aluminum-phosphate-sulphate minerals (APS). APS mineralizations with REE-bearing
svanbergite and florencite originate from supergene alteration. Woodhouseite, goyazite, crandallite and pure svanbergite develop
in hypogene and supergene kaolin deposits. The distinction between hypogene and supergene kaolinization can be made using
various element ratios in kaolin (P vs. S, Zr vs. Ti, Cr + Nb vs. Ti + Fe, and Ce + Y + La vs. Ba + Sr). S,␣Ba, and Sr are
considerably enriched in kaolin during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated
mainly during weathering. Au and Ag become enriched during hypogene kaolinization (advanced argillitization). Kaolinization
is associated with the evolution of the Central Andes as follows: (1) during the Lower Cretaceous kaolinization characterizes
phases of relative tectonic quiescence during mountain building and took place in a miogeosynclinal back-arc basin. The kaolin-bearing
sediments were laid down in flood plain to delta plain environments; (2) in the magmatic arc/back-arc basin (eugeosyncline)
kaolinization was mainly associated with uplift and peneplanation; (3) in the magmatic arc proper, late Miocene kaolinization
of volcanic and volcaniclastic rocks has many features in common with the high sulphidation epithermal Au deposits.
Received: 11 August 1995 / Accepted: 8 May 1996 相似文献
52.
H. Krüger U. Fritze-V. Alvensleben K. J. Fricke H. -H. Loose 《Astrophysics and Space Science》1993,205(1):57-63
We present spectroscopic evolutionary synthesis calculations for starburst galaxies of various metallicities in order to model the broad emission lines HeII 4686 and CIII 4650 produced by Wolf-Rayet (WR) stars in the spectra of WR galaxies. The strengths of both lines strongly decrease with decreasing metallicity. The presence of WR emission features is a clear indicator of very recent star formation less than 4 to 7 × 106 yr ago. Bursts of duration 1 to 5 × 106 yr which lead to an increase in the total stellar mass in the galaxy by 0.1 to 10 % are compatible with the equivalent width of Hell »4686 observed in WR galaxies. 相似文献
53.
Observation of oiled sandy beaches showed the fate of oil released by a tanker collision. The amount of oil extracted depended on timing in the beach erosion and depositing cycle. The recovery of the beaches took about 8 months, but deteriorated again after the arrival of unaccounted oil batches. It is this unaccountable oil which is responsible for chronic oil pollution on the South African coast and possibly other beaches around the world. 相似文献
54.
The Depth Limits of Red Sea Stony Corals: An Ecophysiological Problem (A Deep Diving Survey by Submersible) 总被引:2,自引:0,他引:2
Abstract. Along the Sinai coast of the Red Sea a deep diving survey with the research submersible GEO investigated the depth distribution of stony corals. 47 hermatypic species were identified below 50 m; 9 species extended below 100 m. Their depth distributions are related to light penetration. Observed changes in hermatype growth forms with depth were investigated and interpreted as photo-adaptations. 10 species of ahermatypic corals were found between 100–205 m. Ahermatype growth forms are adaptations to plankton feeding and do not change with depth. 相似文献
55.
C.S. Möller U. Fritze–V. Alvensleben K.J. Fricke D. Calzetti 《Astrophysics and Space Science》2001,276(2-4):799-806
As a tool for interpreting nearby and high-redshift galaxy data from the optical to K-band we present our chemically consistent spectrophotometric evolutionary synthesis models. These models take into account
the increasing initial metallicity of successive stellar generations using recently published metallicity-dependent stellar
evolutionary tracks, stellar yields and model atmosphere spectra. The influence of the metallicity is analysed. Dust absorption
is included on the basis of gas content and abundance as it varies with time and galaxy type. We compare our models with IUE
template spectra and are able to predict UV fluxes for different spectral types. Combining our models with a cosmological
model we obtain evolutionary and k corrections for various galaxy types and show the differences from models using only solar metallicity input physics as a
function of redshift, wavelength band and galaxy type.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
56.
U. Fritze-V. Alvensleben U. Lindner C.S. Möller K.J. Fricke 《Astrophysics and Space Science》2001,276(2-4):1007-1014
We extend our spiral galaxy models, which successfully describe nearby template spectra as well as the redshift evolution
of CFRS and HDF spirals, to include – in a chemically consistent way – the redshift evolution of a series of individual elements.
Comparison with observed DLA abundances shows that DLAs might well be the progenitors of present-day spiral types Sa through
Sd. Our models bridge the gap between high redshift DLA and nearby spiral HII region abundances. The slow redshift evolution
of DLA abundances is a natural consequence of the long SF timescales for discs, the scatter at any redshift reflects the range
of SF timescales from early to late spiral types. We claim that, while at high redshift all spiral progenitor types seem to
give rise to DLA absorption, towards low redshifts, the early-type spirals seem to drop out of DLA samples due to low gas
and/or high metal and dust content. Model implications for the spectrophotometric properties of the DLA galaxy population
are discussed in the context of campaigns for the optical identifications of DLA galaxies both at low and high redshift.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
57.
58.
W. Fricke 《Celestial Mechanics and Dynamical Astronomy》1985,36(3):207-239
Presented is a review of the main achievements of fundamental astrometry from earliest times through the present century. At all times the construction of a celestial reference coordinate system has tormed an important task for describing motions in the sky. The positions of fundamental stars and their centennial variations have been laid down in fundamental catalogues which-beginning with the 18th century-have facilitated famous discoveries and have given rise to the improvement of the techniques of observation. This review culminates in the documentation of the observational achievements of the latest 25 years where in a world-wide campaign of about 50 observatories considerable contributions have been made to the improvement of the current conventional reference coordinate system given in the Fourth Fundamental Catalogue (FK4). The observations analysed in an ambitious program at Heidelberg will yield the FK5 which also will introduce the System of Astronomical Constants adopted by the IAU in 1976. This report ends with an outlook on contributions of space techniques and of radioastrometry of extragalactic sources to progress in fundamental astrometry.Dedication: This review is an extended version of the Dirk Brouwer Lecture 1983 of the Division on Dynamical Astronomy of the American Astronomical Society. With the topics of this lecture the author honors Dirk Brouwer's contributions to astrometry and gratefully acknowledges the support given to astronomy by Ministerialdirigent Karl Otto Schlau in the Government of Baden-Württemberg, Stuttgart, Federal Republic of Germany. 相似文献