Glacial atmospheric CO2 decline in association with decrease of marine sedimentary phosphorus

The environmental and biogeochemical information extracted from the sediments collected from the northern shelf of the South China Sea shows that terrigenous inputs of phosphorus into the sea remained relatively constant, and the variation of phosphorus contents at different depths was caused by climatic and environmental changes. The findings also suggest that the vertical variation of phosphorus content was opposite to those of calcium carbonate and cadmium, and the functional correlation between CO₂ and PO ₄ ³⁻ in seawater was given by calculating the chemical equilibrium, indicating that the accumulation of marine sedimentary phosphorus may have something to do with the variation of atmospheric CO₂. The decreased phosphorus accumulation as well as the correspondingly-increased calcium carbonate content might be one of key factors causing glacial atmospheric CO₂ decline.     

The cenozoic rhyolite-andesite association of the chilean andes

The eruption centres of late volcanism in Chile are situated in two separate areas in the northern and southern High Cordillera. In the north, the ignimbrites of the Rhyolite Formation and the rocks of the « Andesite » Formation occur in about equal proportions, and recent activity is meagre. In the south, the rocks of the « Andesite » Formation predominate, and many volcanoes are in a highly explosive phase of activity. Field relationships, petrological and geochemical data show that the rocks of both Formations are closely related to each other. There is evidence that the magmas of the Rhyolite Formation were formed by fusion of sialic material in the upper parts of the crust. The data for the volcanics of the « Andesite » Formation are inconsistent with their derivation by fractional crystallization of a basaltic parent or by direct mantle derivation involving a single stage process. The authors suggest that the « andesitic » magmas are products of a primary andesitic magma originated by partial fusion of material of the lower crust. Assuming that the « andesitic » magmas of the central parts of the Andes are derived from the upper mantle, this would mean — in the light of the Sr⁸⁷/Sr⁸⁶ data — that the upper mantle in the central region of the Andes is essentially more radiogenic than in other orogenic areas; moroever, it should be very similar in its chemical and Sr⁸⁷/Sr⁸⁶ composition to that of the lower crust.     

87Rb87Sr systematics of a geothermal water-rock association in the Massif Central,France

Rb and Sr concentrations and Sr isotopic composition have been measured in thermo-mineral waters from the Massif Central in France. Rocks and mineral fractions which are thought to be important Sr contributors were also analyzed. The results suggest the waters to be mixtures of two or three components from different reservoirs, which can be associated with possible source rock types like granite and syenodiorite occurring in the region. The strontium isotopic ratios found in the separated minerals of the syenodiorite stratum indicate no chemical fractionation during the water-rock interaction. A RbSr internal isochron age of(265 ± 10) × 10⁶yr is inferred for the Roche d'Enval syenodiorite.     

震后形变和岩石圈流变学结构

岩石圈流变学结构是控制不同构造环境下岩石圈形变的关键因素之一. 随着空间大地测量观测技术的发展, 基于空间大地测量数据的震后形变研究对揭示断裂带内的力学性质和区域性岩石圈流变学结构已成为可能. 该文首先基于岩石力学的摩擦和流变学实验, 对余滑和分布式韧性流的构造物理背景进行了分别阐述, 并介绍了震后形变数值模拟中本构关系和数值模型的发展. 数值模型主要有解析、 半解析和纯数值3类, 涉及的本构关系包括基于速率-状态摩擦准则的余滑以及分布式韧性流中常用的线性流变学模型(麦克斯韦尔体和标准线性固体)和瞬态流变学模型(宏观经验性的伯格斯(Burgers)体和微观幂律流变律). 然后以美国南加州1992年Landers M_W7.3地震和1999年Hector Mine M_W7.1地震震后形变研究为例, 介绍了震后形变的研究进展. 最后回顾了大陆岩石圈流变学结构的研究进展, 并以震后形变研究中的流变学结构(“三明治模型”和“焦糖布丁模型”)存在的争议为例, 说明了岩石圈流变学结构研究所具有的挑战性.     

Stratospheric aerosol dynamics over Kamchatka and its association with geophysical processes

The dynamics of aerosol layers in comparison with geomagnetic and ionospheric data has been studied based on the nighttime single-frequency lidar sounding of the atmosphere over Kamchatka at altitudes of 10 to 90 km. The relation of the aerosol density to solar, magnetic, and ionospheric activity has been studied, and the stratospheric aerosol formation mechanisms have been considered. It has been indicated that variations in the aerosol density correlate with radiowave absorption, perturbations of the ionospheric parameters, and geomagnetic characteristics. The spatial and time scales of aerosol layers have been estimated. The role of stratospheric aerosol as an indicator of geophysical processes is discussed.     

The association of polar mesosphere summer echo layers with tial modes

The occurrence of PMSEs with time of day shows a semi-diurnal variation with minima at 8 and 20 h LT. PMSE layers observed for more than 30 min show an average rate of descent of 2 km h⁻¹. These characteristics suggest the influence of tidal winds. When the observed steady wind and diurnal and semi-diurnal tides at EISCAT are added, the overall magnitude shows a time-variation which matches the occurrence of PMSEs, and the observed rate of descent, approximately 2 km h⁻¹. Atmospheric gravity waves also contribute to the velocity of the neutral wind. When the wave reinforces the background wind, the PMSEs are stronger and descend more rapidly, but when the wave-related velocity opposes the background wind the PMSE is weaker and it descends more slowly.     

Time-dependence of electromagnetic transfer functions and their association with tectonic activity

Laboratory experiments and theoretical considerations have suggested that anomalous dilatant regions can develop in the earth's crust during the period of strain accumulation prior to an earthquake. For moderate and major earthquakes such anomalous regions could be tens or even hundreds of kilometers in extent and should be detectable at the surface with appropriate survey or sounding techniques. Since electrical resistivity is one of the rock properties likely to be strongly modified in a dilatant zone, magnetotelluric impedance and geomagnetic transfer functions might be expected to show time-dependent precursory effects if monitored over a period of time above the focal region of an impending earthquake. Such experiments have been conducted in Japan and in other parts of the world and several examples of resitivity changes in the crust prior to earthquake occurrence have been reported. These results and their association with local seismicity are reviewed in this paper. The available evidence indicates that transfer functions and impedance can display significant time-dependent response to changing crustal conditions in some regions. However, the correspondence between these effects and earthquake occurrence is usually not very clear.Contribution from the Earth Physics Branch No. 858.     

An optimized sequential extraction scheme for molybdenum association in environmental samples

By comparing three sequential extraction procedures, a new optimized extraction scheme for the molybdenum association in environmental samples was proposed.Five operational steps were described as exchangeable(KH_2PO_4+K_2HPO_4: including water-soluble), associated with organic matter(NaOH), Fe–Mn oxides and/or carbonates(HCl), sulfides(H_2O_2) and residue(HNO_3+HF+H_2O_2). An optimized extraction scheme was compared with Tessier's procedure and the Commission of European Communities Bureau of Reference(BCR) was applied to black shales. Results showed Tessier's procedure gave the lowest concentration values for exchangeable molybdenum and the highest values for the residual molybdenum, which could not present the efficiency of the extraction reagents. BCR's procedure showed the highest values in oxidizable molybdenum and presented four fractions of molybdenum, which did not demonstrate the fractions of molybdenum in the black shales in detail. The optimized extraction scheme demonstrated a certain improvement on extraction efficiency over Tessier's procedure for the lowest residual molybdenum, and revealed more featured fraction information of molybdenum in black shales than BCR's. Therefore, after a comparison with other two extraction procedures, the optimized extraction scheme proved suitable for the molybdenum in black shales and it also showed an accurate determination of the molybdenum in the fractions and source of bioavailable Mo.     

Arabian Peninsula-North Pacific Oscillation and its association with the Asian summer monsoon

Using correlation and EOF analyses on sea level pressure from 57-year NCEP-NCAR reanalysis data, the Arabian Peninsula-North Pacific Oscillation (APNPO) is identified. The APNPO reflects the co-variability between the North Pacific high and South Asian summer monsoon low. This teleconnec- tion pattern is closely related to the Asian summer monsoon. On interannual timescale, it co-varies with both the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM); on decadal timescale, it co-varies with the EASM: both exhibit two abrupt climate changes in the middle 1960s and the late 1970s respectively. The possible physical process for the connections between the APNPO and Asian summer monsoon is then explored by analyzing the APNPO-related atmospheric circulations. The results show that with a strong APNPO, the Somali Jet, SASM flow, EASM flow, and South Asian high are all enhanced, and an anomalous anticyclone is produced at the upper level over northeast China via a zonal wave train. Meanwhile, the moisture transportation to the Asian monsoon regions is also strengthened in a strong APNPO year, leading to a strong moisture convergence over India and northern China. All these changes of circulations and moisture conditions finally result in an anoma- lous Asian summer monsoon and monsoon rainfall over India and northern China. In addition, the APNPO has a good persistence from spring to summer. The spring APNPO is also significantly corre- lated with Asian summer monsoon variability. The spring APNPO might therefore provide valuable in- formation for the prediction of Asian summer monsoon.     

Recurrent variations of anomalous oxygen in association with a corotating interaction region

The fluxes of anomalous oxygen (E ranging from 3.5-6.8 MeV/amu), as measured by the EPAC instrument on ULYSSES, show a recurrent variation with the solar rotation period, which is anticorrelated with the fluxes of particles accelerated at the shocks of a corotating interaction region (CIR), and correlated with the fluxes of galactic cosmic rays known to be modulated by the CIR. The amplitude of this variation is much higher than expected for galactic cosmic rays of the same rigidity.     

A late pleistocene to recent rhyodacite-trachybasalt-basaltic latite volcanic association in north-east Papua

The Managalase Plateau in north-east Papua is a faultbounded block of fractured basement metabasalt and basic plutonic rock overlain in the east by some thirty small volcanic centres of late Pleistocene to Recent age which include rhyodacite ash cones and trachybasalt and basaltic latite lava. To the north andesitic strato-volcanoes of Pleistocene and Recent age occur along the margin of the Cape Vogel geosyncline, whereas to the south a series of basaltic latite, alkali basalt and ultra-alkaline lava of Pliocene age margin the Papuan basic-ultrabasic belt. There is a transition, probably by fractional crystallization from alkali basalt through trachybasalt towards trachyandesite, but the basaltic latite and ultraalkaline lava are aberrant offshoots, possibly owing to contamination by phyllite. The « orogenic andesite » shows disequilibrium relations among the minerals including complexly zoned and twinned plagioclase, and common xenocrysts and xenoliths. Their chemistry can be simulated by mixtures of rhyodacite with either alkali basalt or trachybasalt and they are richer in both magnesia and potash than other calc-alkali rock suites. The rhyodacites, however, are of normal cale-alkali character.