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151.
152.
Vyacheslav?V.?AkininEmail author Alexander?V.?Sobolev Theodoros?Ntaflos Wolfram.?Richter 《Contributions to Mineralogy and Petrology》2005,150(1):85-101
Clinopyroxene megacrysts from young melanephelinitic lavas were divided into Cr-rich and Cr-poor suites. Sr, Nd, and Pb isotopic
ratios of leached megacrysts and host lava are indistinguishable from each other and indicate a depleted source. Host lavas
do not display chemical evidence for significant fractional crystallization, which is required to explain the compositional
range of the megacrysts. This rules out a simple cognate genetic relationship between the two, and strictly defines megacrysts
as xenocrysts. The well-defined correlations of trace elements with the Mg-numbers in the megacrysts are interpreted as the
result of extensive fractional/equilibrium crystallization of magma over a large temperature range at near isobaric condition
in the upper mantle. Trace element variations in megacrysts are consistent with fractional crystallization of clinopyroxene
alone for the Cr-rich suite, and clinopyroxene + garnet for the Cr-poor suite from at least two bathes of related melts. Megacrysts
parent magma might represent mantle melts, which were never erupted in their initial composition. 相似文献
153.
154.
Summary In Table I the authors give a list of known deep-focus earthquakes in the eastern Mediterranean. Fig. 1 shows that their epicenters
generally lie in the zones of active volcanoes, as in the regions surrounding the Pacific Ocean; however, their coincidence
with positive gravity anomalies is less evident.
Balch Graduate School of the Geological Sciences: Contribution No. 454. 相似文献
Zusammenfassung In Tabelle I geben die Verff. eine Liste der ihnen bekannten Tiefenbeben im ?stlichen Mittelmeer. Fig. 1 zeigt, dass deren IIerde im Allgemeinen in den Zonen der t?tigen Vulkane liegen, ?hnlich wie in der Umgebung des Pazifischen Ozeans. Dagegen ist deren Zusammenfallen mit positiven Schwereanomalien weniger doutlich.
Riassunto Gli AA. hanno raccolto nella Tab. 1 l'elenco dei terremoti profondi a loro noti del bacino mediterraneo orientale. La Fig. 1 mostra che in generale gli epicentri relativi sono distribuiti nelle zone dei vulcani attivi, analogamente a quanto accade ne'le regioni dell'Oceano Pacifico. Per contro, la connessione con le anomalie gravimetriche positive risulta meno evidente.
Balch Graduate School of the Geological Sciences: Contribution No. 454. 相似文献
155.
Planktonic foraminiferal Mg/Ca ratios and oxygen isotopic compositions of a spliced sediment record from Feni Drift, NE Atlantic Ocean (box core M200309 and piston core ENAM9606) trace late Holocene sea surface temperature (SST) and salinity changes over the past 2400 years. At this location, the variability of SST and oxygen isotopic composition of seawater (δ18Ow) reflects variable northward advection of warm and saline surface waters, which appears linked to climate variability over the adjacent European continent. Our records reveal a general long-term cooling trend. Superimposed on this overall trend, partly higher temperatures and salinities from 180 to 560 AD and 750 to 1160 AD may be ascribed to the Roman and Medieval Warm Periods, respectively. Subsequently, our record displays highly variable surface water conditions; the main Little Ice Age SST minimum is restricted to the 15th and 16th centuries AD. Pervasive multidecadal- to centennial-scale variability throughout the sedimentary proxy records can be partly attributed to solar forcing and/or variable heat extraction from the surface ocean caused by shifts in the prevailing state of the North Atlantic Oscillation (NAO). High salinities in the 17th and 18th centuries are considered to reflect tropical anomalies linked to a southward shift of the Intertropical Convergence Zone, propagating across the North Atlantic Ocean. 相似文献
156.
R. B. Johns T. Belsky E. D. McCarthy A. L. Burlingame Pat Haug H. K. Schnoes W. Richter M. Calvin 《Geochimica et cosmochimica acta》1966,30(12):1191-1222
Several shales and oils ranging in age from 3 million to 2·7 billion years have been investigated for their hydrocarbon content using gas chromatography and mass spectrometry as primary analytical tools. From the Soudan Shale from Minnesota (2·7 × 109yr) the C18, C19, C20 and C21 isoprenoid-alkanes were obtained. The Antrim shale from Michigan (about 265 × 106 yr) yielded the C16, C18, C19, C20 and C21 isoprenoids, as well as a C16 iso-alkane and the C18 and C19 cyclohexyl n-alkanes. The San Joaquin Oil (30 × 106 yr) and the Abbott Rock Oil (3 × 106 yr) contained the C16, C18, C19, C20 and the C18, C19, C20 and C21 isoprenoids respectively. In addition, a series of iso-alkanes (C16−C18), anteiso-alkanes (C16−C18) and n-alkylcyclohexanes (C16−C19) as well as a C21 isoprenoid were obtained from the Nonesuch Seep Oil (1 × 109 yr). This analysis provides a comprehensive picture of the types of biogenic hydrocarbons found in oils and shales of widely differing ages, and in particular, the finding of isoprenoid alkanes in the Soudan Shale furnishes evidence for life processes at that period of geological time. 相似文献
157.
M. Richter 《International Journal of Earth Sciences》1933,24(3-4):271
Ohne Zusammenfassung 相似文献
158.
Rainer Wolf Gerhard R. Richter Alicia B. Woodrow Edward Anders 《Geochimica et cosmochimica acta》1980,44(5):711-717
Six C2M chondrites (Boriskino, Cold Bokkeveld, Erakot, Essebi, Haripura and Santa Cruz) and the C2R chondrite Al Rais were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn. Abundances (relative to Cl chondrites) show a systematic dependence on volatility, apparently reflecting volatile loss during formation of chondrules and other high-T components. Elements of nebular condensation temperature (Tc) > 1200 K are undepleted, those of Tc < 700 K are depleted by a constant factor (0.482 ± 0.049 for C2M's) and elements of intermediate volatility are depleted by intermediate factors. The abundances do not “tend to fall monotonically as a function of [Tc],” as previously claimed by Wai and Wasson (1977) for a more restricted temperature range. For meteorites that have suffered little aqueous alteration (Mighei, Murchison, Murray), the mean abundance of volatiles agrees with the matrix content, but for the more altered meteorites, matrix contents are 20–30% higher. Only a few meteorites deviate appreciably from the mean abundance pattern. Al Rais, a C2R chondrite with a significant metal content, is systematically lower in 12 volatiles, but is enriched in Ni and Pd. Haripura and Erakot are enriched in Bi and Tl, possibly from the late condensate, mysterite. 相似文献
159.
Patterns of basin fill in Triassic turbidites of the Nanpanjiang basin: implications for regional tectonics and impacts on carbonate‐platform evolution 下载免费PDF全文
Daniel J. Lehrmann Daniel H. Chaikin Paul Enos Marcello Minzoni Jonathan L. Payne Meiyi Yu Alexa Goers Tanner Wood Paula Richter Brian M. Kelley Xiaowei Li Yanjiao Qin Lingyun Liu Gang Lu 《Basin Research》2015,27(5):587-612
The Nanpanjiang Basin occurs in a key position for resolving controversies of basin tectonics and patterns of plate assembly at the junction between south China and Southeast Asian plates. Paleocurrent measurements indicate that siliciclastic turbidites in the basin were sourced by the Precambrian Jiangnan uplift to the northeast, the Precambrian Yunkai uplift to the southeast and the Triassic Songma suture to the south. Detrital zircon geochronology reveals Archean (2500 Ma), Paleoproterozoic (1800–1900 Ma), Neoproterozoic (900–1000 Ma) and Paleozoic (420–460 Ma) ages consistent with derivation from the Jiangnan and Yunkai uplifts. A large Permian‐Triassic peak of 250 Ma is present in the southern basin and attenuates northward suggesting derivation from an arc developed along the Songma suture. Sandstone QFL compositions average 65/12/23% and plot in the recycled orogen field except for a few samples in the southern basin that fall in the dissected arc field. The compositions are consistent with derivation from Precambrian basement that includes orogenic complexes. In the southern basin, Middle Triassic turbidites contain greater lithics and feldspars and Lower Triassic turbidites have volcaniclastic composition consistent with derivation from a southerly arc. Our preferred interpretation is evolution from remnant basin to a large peripheral foreland with southward subduction and convergence with Indochina along the Songma suture. The previously proposed Dian‐Qiong zone is not a suture as its map location places it within carbonate platforms bounded by identical stratigraphy. The Nan‐Uttaradit zone is too distant to have provided voluminous siliciclastic flux to the basin. The Nanpanjiang Basin provides an example of the evolution of an exceptionally large foreland with far‐field rejuvenation of Precambrian uplifts and carbonate platforms that were significantly influenced by siliciclastic flux. The timing and pattern of turbidite basin fill impacted platform evolution by enabling margin progradation in areas proximal to siliciclastic sources, whereas platforms distant from sources were driven to aggradation and extreme relief with large‐scale gravitational sector collapse. 相似文献
160.
In continuation of part I of our investigation a field of 0.8 near the galactic north pole is investigated with two large photographic telescopes of very different optical constants. The field contains the cluster Abell 1775. Statistics and photometry confirm the results of part I. The fraction of optical compact galaxies up to the identification magnitude 18m9 (B) is found to be more than 30% of the total number of cluster galaxies. The data for a secondary photometric sequence, which had to be determined for the photometry of the galaxies, are presented. 相似文献