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991.
J. Nuzzo M. Hyman M. W. Rowe M. N. Rao R. L. Palma J. Westrich 《Journal of Earth System Science》2000,109(1):89-94
We have measured the abundance and isotopic composition of xenon in petroleum samples from the Shell Bullwinkle Field off
the coast of Louisiana. We used an oxidation and purification procedure designed to insure complete extraction and clean up
of xenon from the petroleum.
The xenon isotopic composition was found to be similar to the atmospheric value for one petroleum sample. While the results
of the second sample suggest possible enrichment of the heavier isotopes, the errors associated with these excesses preclude
a definitive statement to that effect. No monoisotopic enrichment in129Xe was detected in either sample, the presence of which might have allowed us to deduce the petroleum age. Our results represent
only the second xenon measurement from petroleum, and the concentrations are within the range of values published in the earlier
report. 相似文献
992.
O. L. Morozov 《Lithology and Mineral Resources》2000,35(2):163-182
Based on the study of various facies of ancient and modern oceanic sediments, the Ce/La versus Zr/Y criterion is proposed
to discriminate the principal genetic groups of sedimentary rocks in foldbelts and to determine their geodynamic formation
conditions. The structure and composition of siliceous, clayey and fineclastic tuffaceous rocks from various complexes of
paleoaccretionary wedge in the Pekul’nei Range (Chukotka) are discussed. Lithological and geochemical studies of sedimentary
rocks in the Pekul’nei Range allowed us to trace the regular variations in rock sections depending on (1) propagation of oceanic
plate from the spreading center toward the convergent boundary for paleooceanic rock complexes and (2) sedimentation regime
and provenances for rocks deposited above the convergent plate boundary. 相似文献
993.
Olivine-liquid equilibrium 总被引:6,自引:5,他引:6
A number of experiments have been conducted in order to study the equilibria between olivine and basaltic liquids and to try and understand the conditions under which olivine will crystallize. These experiments were conducted with several basaltic compositions over a range of temperature (1150–1300° C) and oxygen fugacity (10?0.68–10?12 atm.) at one atmosphere total pressure. The phases in these experimental runs were analyzed with the electron microprobe and a number of empirical equations relating the composition of olivine and liquid were determined. The distribution coefficient 1 $$K_D = \frac{{(X_{{\text{FeO}}}^{{\text{Ol}}} )}}{{(X_{{\text{FeO}}}^{{\text{Liq}}} )}}\frac{{(X_{{\text{MgO}}}^{{\text{Liq}}} )}}{{(X_{{\text{MgO}}}^{{\text{Ol}}} )}}$$ relating the partioning of iron and magnesium between olivine and liquid is equal to 0.30 and is independent of temperature. This means that the composition of olivine can be used to determine the magnesium to ferrous iron ratio of the liquid from which it crystallized and conversely to predict the olivine composition which would crystallize from a liquid having a particular magnesium to ferrous iron ratio. A model (saturation surface) is presented which can be used to estimate the effective solubility of olivine in basaltic melts as a function of temperature. This model is useful in predicting the temperature at which olivine and a liquid of a particular composition can coexist at equilibrium. 相似文献
994.
The origin of scapolite in the regionally metamorphosed rocks of Mary Kathleen,Queensland, Australia
Scapolite at Mary Kathleen (North-Western Queensland) occurs in calcareous and non-calcareous metapelites, acid and basic metavolcanics and metadolerites. Graphical treatment of the relationship between scapolite composition (Me%) and the host rock oxide ratios CaO/Na2O and Al2O3/(CaO + Na2O) reveals the following points:
- The calcareous metapelites are also very sodic.
- Scapolite in calcareous metapelites is more marialitic than that in low-calcium equivalents.
- In graphs of Me% against CaO/Na2O and Al2O3/(CaO + Na2O) the metasediments and the metaigneous rocks show markedly different trends.
995.
996.
The presence of Dicynodontia in Sinkiang was first made manifest by the beautiful skull described in the same number of the Bulletin, (see above 563) as Dicynodon sinkianensis sp. nov. Recently, a second skull also collected by 相似文献
997.
998.
Duobaoshan porphyry copper deposit,situated in Nen-jiang County of Heilongjiang Province,Northeast China,liestectonically in the Mongolian-Okhotsk geosyncline.Duobaoshan porphyry copper ore field consisting ofDuobaoshan copper deposit and Tongshan copper deposit con-tains rich copper associated with molybdenum,gold,silverand osmium (Os1 87) . In this sense,this porphyry copper orefield will turn into a large industrial base of copper,gold,sil-ver and osmium.At present,in Duobaoshan porphy… 相似文献
999.
Thomas A. Munroe Donald M. Baltz Robert L. Allen Steve W. Ross 《Estuaries and Coasts》2000,23(4):439-448
Two species of tonguefishes,Symphurus plagiusa (Linnaeus 1766) andSymphurus civitatium Ginsburg 1951, occur sympatrically and sometimes syntopically in shallow water habitats in North Carolina and Louisiana estuaries. In North Carolina, approximately 2% of 430 small (<75 mm SL) tonguefishes collected wereS. civitatium, while in Barataria Bay, Louisiana, this species was more abundant and cosmopolitan in distribution than wasS. plagiusa, comprising over 82% of 3,564 tonguefishes collected with a small beam trawl over a 2-yr period. Historical literature has regardedS. plagiusa as the only tonguefish species inhabiting inshore waters in both regions. Presence of a secondSymphurus species in shallow estuaries has been overlooked, most probably due to difficulties in identifying early post-settlement juveniles because both species have similar morphologies and overlapping dorsal-fin and anal-fin ray counts. Juveniles can be readily recognized by differences in number of caudal-fin rays (10 inS. plagiusa versus 12 inS. civitatium), especially when used in combination with pigmentation patterns and posterior extent of the jaws relative to the posterior margin of the lower eye. The most distinctive pigmentation difference between juveniles of these two species (allowing for accurate identifications of over 98% of juveniles) is the absence inS. civitatium (12–61 mm SL) of a series of melanophores overlying pterygiophore regions of the dorsal and anal fins on the blind side. This feature contrasts markedly with that of juvenileS. plagiusa (12–65 mm SL), which are characterized by two interrupted, diagonal series of dark chromatophores converging, but not merging, with posterior tapering of the body. Occurrence of two sympatric species of tonguefishes in estuarine environments in the northcentral Gulf of Mexico and southeastern U.S. potentially compromises results of earlier ecological and distributional studies that assumed presence of only a single tonguefish species in these regions. 相似文献
1000.
Janet M. Fischer Tara Reed-Andersen Jennifer L. Klug Alice G. Chalmers 《Estuaries and Coasts》2000,23(4):565-571
Geomorphology may be an important predictor of vegetation pattern in systems where suceptibility to disturbance is unevenly
distributed across the landscape. Salt marsh communities exhibit spatial pattern in vegetation at a variety of spatial scales.
In coastal Georgia, the low marsh is a virtual monoculture ofSpartina alterniflora interspersed with patches of species that are more typical of the high marsh. These localized disturbances are most likely
created by wrack mats, mats of dead vegetation which can compact and smother underlying vegetation creating bare patches for
colonization by high marsh species. We investigated the spatial pattern of disturbed patches along a 2 km section of Dean
Creek, a tidal creek at the southwestern end of Sapelo Island, Georgia, U.S. We used a discriminant model to explore the relationship
between tidal creek morphology (e.g., the presence of drainage channels and creek bends) and the spatial distribution of disturbed
patches. The model predicted vegetation pattern along the creek with relatively high accuracy (>70%). Areas where water movement
is slowed or multidirectional (e.g., along creek bends and near drainage channels) were most susceptible to disturbance. Our
findings suggest an important functional linkage between geomorphology and vegetation pattern in salt marsh communities. 相似文献