西风带研究的重要意义

西风带作为北大西洋气候区和东亚季风气候区之间的联系纽带,对东亚季风气候和西风带气候具有重要影响,西风带在一定意义上控制着东亚季风的北界。西风环流与青藏高原相互作用,对亚洲季风区气候乃至全球气候都有极其深刻的影响。西风环流在冰期-间冰期旋回中的位置、强度的剧烈变化对东亚季风气候和全球气候影响显著,对季风降水、西风带降水时空分布及亚洲粉尘活动和黄土形成、堆积等都有非常重要的意义。     

Harmful Ciliates and Dominant Genus in Culture Ponds of Young Abalone

By using the methods of qualitative and quantitative analysis, the species composition and dominant genus of harmful, ciliates in young abalone culture ponds are studied. Totally 68 species of ciliates, belonging to 3 classes, 16 orders and 46 genus, are found. The dominant ciliate species are Aspidisca leptaspis, Vorticella sp. and Euplotes rariseta. During the young abalone cultivation, the numbers of young abalones increase first,and then show a trend of decreasing. The relationship between the density and composition of ciliates and the density of algae in the young abalone culture ponds is also discussed.     

Bulk Chemical Composition of the Ningqiang Carbonaceous Chondrite： An Issue of Classification

The Ningqiang meteorite is a fall carbonaceous chondrite, containing various Ca-, Al-rich inclusions that usually escaped from secondary events such as high-temperature heating and low- temperature alteration. However, it has not yet been classified into any known chemical group. In order to address this issue, 41 elements of the bulk Ningqiang meteorite were analyzed using inductively coupled plasma mass spectrometry （ICP-MS） and inductively coupled plasma atom emission spectrometry （ICP-AES） in this study. The Allende （CV3） carbonaceous chondrite and the Jilin （H5） ordinary chondrite were also measured as references, and our analyses are consistent with the previous results. Rare earth and other refractory lithophile elements are depleted in Ningqiang relative to both Allende and mean CK chondrites. In addition, the REE pattern of Ningqiang is nearly flat, while that of Allende shows slight enrichment of LREE relative to HREE. Siderophile elements of Ningqiang are close to those of mean CK chondrites, but lower than those of Allende. Our new analyses indicate that Ningqiang cannot be classified into any known group of carbonaceous chondrites, consistent with previous reports.     

Discovery and Significance of High CH4 Primary Fluid Inclusions in Reservoir Volcanic Rocks of the Songliao Basin, NE China

Comparing compositions of the fluid inclusions in volcanic rocks to the contents and isotopes of the gases in corresponding volcanic reservoirs using microthermometry, Raman microspectroscopy and mass spectrum analysis, we found that： （1） up to 82 mole% methane exists in the primary inclusions hosted in the reservoir volcanic rocks; （2） high CH4 inclusions recognized in the volcanic rocks correspond to CH4-bcaring CO2 reservoirs that are rich in helium and with a high ^3He/^4He ratio and which show reversed order of 813C in alkane; （3） in gas reservoirs of such abiotic methane （〉80%） and a mix of CH4 and CO2, the enclosed content of CH4 in the volcanic inclusions is usually below 42 mole%, and the reversed order of δ^13C in alkane is sometimes irregular in the corresponding gas pools; （4） a glassy inclusion with a homogeneous temperature over 900℃ also contains a small portion of CH4 although predominantly CO2. This affinity between gas pool and content of inclusion in the same volcanic reservoirs demonstrates that magma-originated gases, both CH4 and CO2, have contributed significantly to the corresponding gas pools and that the assumed hydrocarbon budget of the bulk earth might be much larger than conventionally supposed.     

Fluidization： An Important Process in the Formation of the Qiyugou Au-bearing Breccia Pipes in Central China

Fluidization processes based on experiments are reviewed to gain some useful insights and comparisons with those that occur in hydrothermal systems. Field and petrographic work, and microscope observation were carried out on samples from the Qiyugou Au-bearing breccia pipes from the East Qinling region, Henan Province. Evidence from macro- and micro-textures suggests that the style of breccias in the Qiyugou area can be grouped into three types： （1） jigsaw fit-stockwork texture, in which the interval between clasts is marked by fractures or filled with calcite or quartz veins; （2） larger breccias that are supported by smaller breccias, rock flour and alteration materials; in this type clasts moved over short distances, creating open spaces; （3） fluidized texture, where the clasts of different lithologies have rounded shapes. These observations are compared with those resulting from experiments on fluidization processes. The results of this comparison suggest that fluidization is an important geological process in the formation of the Qiyugou Au-bearing breccia pipes and gold mineralization. In addition, fluidization processes such as expansion, bubbling, slugging, channeling and spouting must have contributed to the formation of the pipes and were conducive to the development of gold mineralization. In the Qiyugou breccia pipes, gold mineralization occurs as disseminations, in stockwork veins, and open space infills. The ore zones form subparallel sheets that are nearly perpendicular to the walls of the pipes.     

A Study of Mesoproterozoic Iron Cosmic Micro-spherules from 1.8 Ga and 1.6 Ga Old Strata in the Ming Tombs District, Beijing

Numerous iron cosmic micro-spherules have been discovered from Mesoproterozoic strata including the Changzhougou Formation(1.8 Ga) and the Dahongyu Formation(1.6 Ga) of the Ming Tombs district,Beijing.There are 1 to 30 grains of cosmic spherules per 2 kg of a sandstone sample taken from the bottom of a coarse sandstone bed of the Changzhougou Formation and 56 grains per 3.69 kg of a rock sample from silicified carbonate rocks of the Dahongyu Formation.The surface textures of cosmic spherules analyzed by means of the secondary electron imagery are identical with those reported from references either domestic or abroad.So far the geo-ages of 1.8 Ga and 1.6 Ga of cosmic spherules from the Changzhougou and Dahongyu formations might be older than those reported in the world.Table 1 gives the electron probe analysis data of cosmic spherules for 30 spherule grains and 44 testing points as follows(%):FeO,80-95;Cr_2O_3;0-9.56;NiO,0-0.78;CoO,0-0.46; indicating that the Cr_2O_3 content is higher and FeO content lower in the Changzhougou Formation than in the Dahongyu Formation.The helium isotopic data of cosmic spherules as well as their host rocks vary greatly between the Changzhougou and the Dahongyu formations as shown in Table 2.The data of cosmic spherules of the Changzhougou Formation vs the Dahongyu Formation are 57.5/1.23 in ~3He/~4He(10~(-8));and 55.54/809.60 in ~4He(10~(-6)cm~3STP/g);those of coarse sandstone of the Changzhougou Formation vs silicified carbonate of the Dahongyu Formation are 3.39/2.59 in ~3He/~4He(10~(-8)) and 4.56/2.34 in ~3He(10~(-6)cm~3STP/g).The ratio of analytic data of helium isotopes are different for cosmic spherules and their host rocks;for example,the ~3He/~4He(10~(-8)) values are 16.96 and 0.48,and the ~4He (10~(-6)cm~3STP/g) are 12.18 and 345.98 for the Changzhougou and Dahongyu formations respectively.It was reported that the world's oldest micrometeorites had been found in the Meso-Proterozoic Satakunta Formation,Finland.However,the cosmic spherules from the Meso-Proterozoic Changzhougou and Dahongyu formations are 200 to 400 Ma older than those from the Satakunta Formation.Besides,one carbonaceous chondrite grain was discovered for the first time as the earliest remain formed in the solar nebula from the Dahongyu Formation.     

Carbonate Sequence Stratigraphy of a Back-Arc Basin： A Case Study of the Qom Formation in the Kashan Area, Central Iran

The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid-Tertiary back-arc basin. There are two second-order sequences (designated as SS1 and SS2) and five third-order sequences (designated as S1-S5). Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and lowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined (S1 to S5 individually corresponding to A-C1, C2-C4, D-E, the lower and upper portions of F); a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing: (1) a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; (2) a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and (3) a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences (S1 and S3) of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences (S2 and S4-S5) of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.     

SOME RELATIONS BETWEEN ASYMMETRIC STRUCTURE AND MOTION OF TYPHOONS

The analysis of the SPECTRUM (Special Experiment Concerning Typhoon Recurvature andUnusual Movement) data indicates that the structure of recurving target typhoons 9015 (Abe),9019(Flo) and 9020 (Gene) at different stages of moving processes showed different motion features.Ondifferent time scales,temporal variations of typhoon structure and motion speed displayed differentfeatures.     

CHARACTERISTICS OF TURBULENCE SPECTRA IN DIFFERENT WEATHER PROCESSES UNDER UNSTABLE CONDITIONS

In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such asturbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculatedand their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results areobtained and compared with others' results.     

THE IMPACT OF MID-LATITUDE CIRCULATION OVER THE TIBETAN PLATEAU ON THE TRACK OF TYPHOON OVER THE NORTHWEST PACIFIC

There is a close relationship between variation of middle latitude synoptic system over theTibetan Plateau and movement of typhoon over the Northwest Pacific.This paper tries to discussthe mechanism of it through the numerical simulation and dynamic diagnosis.25-year statistical results during the period from 1970 to 1995 indicate that the relationshipbetween middle latitude circulation over the Plateau and the track of typhoon over the NorthwestPacific are as follows.When longwave trough in 500 hPa isobaric surface over the Plateau.it isfavourable to typhoon's westward movement:on the contrary,large scale anticyclone over thePlateau is favourable to typhoon's recurvature.We simulated the typhoon under these two flowpatterns with MM5 model.Numerical simulation results showed that:(a)Longwave trough on500 hPa surface over the Plateau makes subtropical high extended westward so as to typhoon southto high moves westward in easterly steering flow.(b)Anticyclone over the Plateau will bringabout the longwave trough developing along the east coast of Asia,it'will usually cause typhoonrecurring in front of the developed trough.In addition,the results of dynamic diagnosis show the physical mechanism on impact ofsynoptic system over the Plateau on the downstream synoptic system,that is,the transport ofdisturbance kinetic energy over the upstream Plateau makes the downstream trough developed.And then it affects the steering flow of typhoon.Because of existence of the high ridge over thePlateau.the energy transport channel moves to north.On the contrary,the trough exists over thePlateau,the energy transport channel moves to south.The southerly in front of trough over thePlateau and the southerly in the east part of typhoon transport low potential vorticity of lowlatitude into subtropical high.That is beneficial to development of subtropical high and affectstyphoon's movement.These results fully reflect the impact of interaction between mid-latitude andlow latitude on synoptic system.