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71.
Otto Wilckens 《International Journal of Earth Sciences》1924,15(4):315-317
Ohne Zusammenfassung 相似文献
72.
73.
Otto Jaekel 《International Journal of Earth Sciences》1920,10(4-8):97-111
Ohne Zusammenfassung 相似文献
74.
Ohne Zusammenfassung 相似文献
75.
76.
Otto Ludwig 《International Journal of Earth Sciences》1929,20(1):36-65
Ohne Zusammenfassung 相似文献
77.
Ohne ZusammenfassungMit 1 Textabbildungen 相似文献
78.
Brandon G. Watts Marvin E. Bennett Otto C. Kopp Gerald L. Mattingly 《Geoarchaeology》2004,19(1):47-69
Seventeen basalt grindstone fragments from central Jordan's Karak Plateau were studied. Most of these artifacts are vesicular or amygdaloidal with calcite as the dominant mineral filling the voids. The major minerals are olivine (with iddingsite rims), plagioclase, clinopyroxene, magnetite, and apatite. Glass is present in some samples. One basalt fragment is quite different in appearance and composition and may have come from flows closer to the Dead Sea. Grindstone fragment compositions plot in the tephrite‐basanite and basalt fields. A plot of the concentrations of niobium, zirconium, and yttrium reveal that the sample compositions plot in the “within‐plate alkali basalt” and “within‐plate tholeiite” fields. The acquisition of basalts for preparing such implements appears to have been random. Some may have been introduced through trade and migration. Archaeological and environmental studies on the Karak Plateau are urgently needed because Jordan's population growth and economic development are destroying many sites and their environmental contexts. © 2004 Wiley Periodicals, Inc. 相似文献
79.
Contributions of groundwater conditions to soil and water salinization 总被引:23,自引:2,他引:21
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or
human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration,
hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction
of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition.
These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden
in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In
all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a
small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater
flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges
in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region,
Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction
with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas
or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path
and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed
trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate
precipitation and dissolution of capillary salts.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
80.
Interaction between crustal-derived felsic and mantle-derived mafic magmas in the Oberkirch Pluton (European Variscides, Schwarzwald, Germany) 总被引:5,自引:1,他引:4
R. Altherr F. Henjes-Kunst C. Langer J. Otto 《Contributions to Mineralogy and Petrology》1999,137(4):304-322
The composite Oberkirch pluton consists of three compositionally different units of peraluminous biotite granite. The northern
unit is relatively mafic (SiO2∼64%) and lacks cordierite. The more felsic central and southern units (SiO2=67.8 to 70.4%) can only be distinguished from each other by the occurrence of cordierite in the former. Mafic microgranular
enclaves of variable composition, texture and size occur in each of these units and are concentrated in their central domains.
Most abundant are large (dm to m) hornblende-bearing enclaves with dioritic to tonalitic compositions (SiO2=50.8 to 56.3 wt%; Mg#=63 to 41) and fine grained doleritic textures that suggest chilling against the host granite magma.
Some of these enclaves are mantled by hybrid zones. Less common are microtonalitic enclaves containing biotite as the only
primary mafic phase (SiO2=53.7 to 64.4%) and small hybrid tonalitic to granodioritic enclaves and schlieren. Synplutonic dioritic dikes (up to 6 m
thick) with hybrid transition zones to the host granite occur in the southern unit of the pluton. In chemical variation diagrams,
samples from unmodified hornblende-bearing mafic enclaves and dikes form continuous trends that are compatible with an origin
by fractionation of olivine, clinopyroxene, hornblende and plagioclase. Chemical and initial isotopic signatures (e.g. high
Mg#, low Na2O, ɛNd=−1.2 to −5.1, 87Sr/86Sr=0.7055 to 0.7080, δ18O=8.0 to 8.8‰) exclude an origin by partial melting from a mafic meta-igneous source but favour derivation from a heterogeneous
enriched lithospheric mantle. Samples from the granitic host rocks do not follow the chemical variation trends defined by
the diorites but display large scatter. In addition, their initial isotopic characteristics (ɛNd=−4.5 to −6.8, 87Sr/86Sr=0.7071 to 0.7115, δ18O=9.9 to 11.9‰) show little overlap with those of the diorites. Most probably, the granitic magmas were derived from metapelitic
sources characterized by variable amounts of garnet and plagioclase. This is suggested by relatively high molar ratios of
Al2O3/(MgO+FeOtot) and K2O/Na2O, in combination with low ratios of CaO/(MgO+FeOtot), variable values of Sr/Nd, Eu/Eu*[=Eucn/(Smcn × Gdcn)0.5] and (Tb/Yb)cn (cn=chondrite-normalized) as well as variable abundances of Sc and Y. Whole-rock initial isotopic signatures of mafic microtonalitic
enclaves (ɛNd=−4.6 to −5.2; 87Sr/86Sr=0.7060 to 0.7073; δ18O ∼8.1‰) are similar to those of the low ɛNd diorites. Plagioclase concentrates from a granite sample and a mafic microtonalitic enclave are characterized by initial
87Sr/86Sr ratios that are significantly higher than those of their bulk rock systems suggesting incorporation of high 87Sr/86Sr crustal material into the magmas. Field relationships and petrographic evidence suggest that the Oberkirch pluton originated
by at least three pulses of granitic magma containing mafic magma globules. In-situ hybridization between the different magmas
was limited. Late injection of dioritic magma into the almost solidified granitic southern unit resulted in the formation
of more or less continuous synplutonic dikes surrounded by relatively thin hybrid zones.
Received: 30 April 1999 / Accepted: 6 August 1999 相似文献