Microstructure characteristics of illite from Chuanlinggou Formation of Changcheng System in Jixian County, Tianjin City

The microstructure charateristics of illite from the Chuanlinggou Formation of Changcheng System (Chch) in Jixian County, Tianjin City has been studied by means of high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray energy dispersive spectrum (EDS) and X-ray powder diffraction (XRD). The Kübler index of "illite crystallinity" is 0.505°△2θ, which indicates that the host rock is in a middle diagenetic stage. The chemical analyses of EDS for illite studied indicate a heavily absent in interlayer cation and an average chemical formula of K0.57(Al1.80Mg0.42Fe2 0.12)Σ=2.34 (Si2.92Al1.08)Σ=4O10(OH)2. It is found, from one-dimensional lattice images, that the layers of illite not only stack in a flat way but also in a curving way. A "matting fabric" illite structure results from stacking faults. Combined with SAED analysis the illite studied can be affirmed as 1M illite. The two-dimensional lattice images are obtained from [100] and [110] incidences, whose lattice images have the same d-values but different intersecting angles. The two-dimensional lattice image with [100] incidence is orthogonal to each other, whilst that with [110] incidence is oblique. This paper provides some important structure information of authigenic clay minerals for the well-known mesoproterozoic section of Jixian County.     

Model of vibrational level populations of Herzberg states of oxygen molecules at heights of the lower thermosphere and mesosphere

The paper presents a model of the kinetics of electronically excited O₂(c¹Σ_u⁻,v), O₂(A′³Δ_u,v), O₂(A³Σ_u⁺,v) molecules at heights of the lower thermosphere and mesosphere with allowance for electronic excitation transfer processes during molecular collisions. The model is used to calculate the relative O₂(A³Σ_u⁺,v) and O₂(A′³Δ_u,v) populations at heights of 80–110 km. The calculated populations are compared with the available literature results on experimental estimates, and good agreement is obtained. It is shown how the increase in the quenching rates of the considered states by oxygen atoms affects the calculation results.     

The middle-long term prediction of the February 3, 1996 Lijiang earthquake (MS=7) by the "criterion of activity in quiescence"

IntroductionIn the book Future CataS~ologr published in 1992, we proposed a viewpoiflt on using the"criterion of activity in quiescence" to predict big eathquake (MsZ7) (GUO, et al, 1992), and predicted in the book that in futore several years or in ten years a big earthquake (Ms27) will be possible to occur in the Zhongdian and nearby in Yunnan Province. In the 1994 nation-wide earthquake tendency consultation meeting we pointed out, once more, in the Zhongdian region of Yunnan Province…     

Distribution of Lg coda Q in Xinjiang and its adjacent regions

In this study, we collected 1 156 broadband vertical components records at 22 digital seismic stations in Xinjiang region, ürümqi station, and 7 stations in the adjacent regions during the period of 1999–2003. The records were firstly processed by the stacked spectral ratio method to obtain Q ₀ (Q at 1 Hz) and the frequency correlation factor η corresponding to each path. Based on the results, the distribution images of Q ₀ and η in 1°×1° grids for Xinjiang region were gained by the back-projection technique. The results indicate that Q ₀ is high (300–450) in the Tarim platform and marginal Siberian platform, while Q ₀ is low (150–250) in the southern regions as west Kunlun fold system and Songpan-Ganzi fold system. In the northern regions as Junggar fold system and Tianshan fold system, Q ₀ is also low (250–300) and η varies between 0.5 and 0.9. Foundation item: National Natural Science Foundation of China (49974012) and Joint Seismological Science Foundation of China (604004).     

Spatial and temporal characteristics of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression

The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure,     

The structure and ability of the China Seismological Gravity Monitoring System

IntroductionMore than 30 years has passed since gravity method was used to Study the eanhquake prediction in China in later 1960s (In America, Germany, Japan and the former Soviet Union etC. it haspassed nearly half a century). In this 30 years the most remarkable success achieved are as follows.First, in the cognition aspect, the questions whether the gravity will change or not before earthquake and how much the magnitUde of change has been answered. TO the fial queStion, the answer is p…     

Changes in source parameters of foreshocks and aftershocks of the 2001 Ms=6.0 Yajiang,Sichuan, earthquake

In this paper changes in focal mechanisms) parameters of wave spectra, and stress drops for the Ms=5.0 forcshock and Ms=6.0 mainshock in February 2001 in Yajiang County, Sichuan, and seismicity in cpiccntral region are studied. Comparison of focal mechanisms for the Yajiang earthquakes with distribution patterns of aftcrshocks, the nodal plane Ⅰ, striking in the direction of NEN, of the Yajiang M=5.0 event is chosen as the faulting plane, the nodal plane Ⅱ, striking in the direction of WNW, of the M=6.0 event as the faulting plane. The strikes of the two faulting planes are nearly perpendicular to each other. The level of stress drops in the cpicentral region before the occurrence of the M=6.0 earthquake increases, which is consistent with increase of seismicity in the epicentral region. The rate decay of the Yajiang earthquake sequence, changes in wave spectra for foreshocks and aftershocks,and focal mechanisms are complex.     

Effects of abnormally high heat stress on petroleum in reservoir

An igneous intrusion of 94m thick was discovered intruding into the Silurian sandstone from Tazhong 18 Well. The petroleum previously preserved in the Silurian sandstone reservoir was altered into black carbonaceous bitumen by abnormally high heat stress induced by the igneous intrusion. The reflectance of the carbonaceous bitumen reaches as high as 3.54%, indicating that the bitumen had evolved into a high thermal evolution level. Similar to the Silurian samples from the neighboring Tazhong 11, Tazhong 12, Tazhong 45 and Tazhong 47 wells, the distribution of C₂₇, C₂₈ and C₂₉ steranes of the carbonaceous bitumen is still “V”-shaped and can still be employed as an efficient parameter in oil source correlation. The “V”-shaped distribution indicates that the hydrocarbons from the Tazhong 18 and the neighboring wells were all generated from the Middle-Upper Ordovician hydrocarbon source rocks. However, the oil source correlation parameters associated with and terpanes had been changed greatly by the high heat stress and can no longer be used in oil source correlation. The δ ¹³C values of the petroleum from the neighboring wells are between −32.53%. and −33.37%., coincident with those of the Paleozoic marine petroleum in the Tarim Basin. However, the δ ¹³C values of the carbonaceous bitumen from the Tazhong 18 Well are between −27.18%. and −29.26%., isotopically much heavier than the petroleum from the neighboring wells. The content of light hydrocarbons (nC₁₄−nC₂₀) of the saturated hydrocarbon fraction in the carbonaceous bitumen is extremely higher than the content of heavy hydrocarbons. The light/heavy hydrocarbon ratios (ΣnC₂₁ ⁻/ΣnC₂₂ ⁺ are between 4.56 and 39.17. In the saturated fraction, the even numbered hydrocarbons are predominant to the odd numbered, and the OEP (Odd to Even Predominance) values are between 0.22 and 0.49. However, the content of light hydrocarbons in the petroleum from the neighboring wells is relatively low and the content of the even numbered hydrocarbons is almost equal to that of the odd numbered. Compared with the samples from the neighboring wells, the abundance of non-alkylated aromatic hydrocarbons, such as phenanthrenes, and polycyclic aromatic hydrocarbons (PAHs), such as fluoranthane, pyrene, benzo[a]anthracene and benzofluoranthene, are relatively high. Supported by the National Key Basic Research and Development Project (Grant No. 2005CB422103)     

The Early Paleozoic Tiefosi syn-collisional granite in the northern Dabie Orogen:Geochronological and geochemical constraints

The Tiefosi granitic pluton is located 5 km northwest of Xinyang City,northern Dabie Orogen,and was emplaced in the Proterozoic Qinling Group. SHRIMP zircon U-Pb dating suggests its crystallization at 436 ± 11 Ma. It is composed of monzogranite and syenogranite containing some amounts of muscovite and few mafic minerals. The rocks are characterized by high and restricted SiO2 content,low FeO,Fe2O3 and MgO contents,high K2O/Na2O ratio,and display high-K calc-alkaline and peraluminous (ACNK>1.1) characteristics. They are generally enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). They can be divided into three groups in light of rare earth elements (REE) and trace elements. Group I is moderate in ΣREE and characterized by the absence of Eu anom-aly,high (La/Yb)N ratio,and moderate Rb/Sr and Rb/Ba ratios. Group Ⅱ has moderately negative Eu anomaly,low (La/Yb)N ratio and high ΣREE contents,Rb/Sr and Rb/Ba ratios. Group Ⅲ displays positive Eu anomaly,moderate (La/Yb)N ratio,and low ΣREE,Rb/Sr and Rb/Ba ratios. The calculated εNd(440Ma) values of the rocks vary from 8.8 to 9.9 and Nd depleted mantle model ages are about 2.0 Ga,which resemble those of the paragneisses from the Qinling Group. The results indicate that the Tiefosi granite is crust-derived,syn-collisional S-type granite. Generation of Group I was related to low degree melting of the Qinling Group,while Group Ⅱ was formed by fractionational crystallization of plagioclase from Group I magmas,and Group Ⅲ resulted possibly from magma mingling with plagioclase cumulates. The Tiefosi granite was formed within crustal level related to the collision between the North China and South China blocks in the Early Paleozoic time.     

Application of the method of dynamic calibration for IMS stations in regions with lower seismic activity

The Method of Dynamic Calibration (MDC) of stations of the International Monitoring System (IMS) was developed for calibrating regions where no underground nuclear explosions were carried out, with the purpose of providing conditions for implementation of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in nontrivial cases. Initially, the MDC had been presented in [Kedrov, 2001; Kedrov et al., 2001; Kedrov O.K. and Kedrov E.O., 2003] and then considered in detail in [Kedrov et al., 2008]. The core of MDC relates to adapting diagnostic parameters for the identification of underground nuclear explosions (UNE) and earthquakes elaborated for the region of Eurasia, taken as a basic region (BR), for other researched regions that differ from BR in the character of the attenuation of seismic waves. The unique characteristic of this method lies in the fact that calibration of diagnostic parameters with the help of attenuation coefficients b _Δ at varied source-station traces is implemented using only natural seismicity data within the limits of an explored region and does not require special underground chemical explosions. The MDC algorithm is implemented in the research program ”Kalibr”, which was tested by using the experimental data from Eurasia region. It is shown in this work that MDC can be used for calibration of regions where a very low level of natural seismicity is observed. According to the results of the calibration of diagnostic parameters at IMS stations in several regions of North America, Africa, and Asia, the approximate classification of propagation conditions for seismic signals at source-station traces in platform and tectonically active regions is made. The results for the development of two research programs, “Spektr” and “Signal”, are presented; this software is intended for automation of calculation procedures for spectral diagnostic parameters of UNEs’ and earthquakes’ identification by amplitude spectra of P waves and by the maximal amplitudes of P, S, and LR signals. The application of these programs allowed us to accelerate the whole calibration procedure for a particular source-station trace using the ”Kalibr” program.     

REE and <Emphasis Type="Italic">ε</Emphasis><Subscript>Nd</Subscript> of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and ¹⁴³Nd/¹⁴⁴Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents (ΣREE), LREE/HREE ratio and cerium anomaly (δCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio <1, δCe >0.85, ΣREE <400 μg/g, LREE/HREE ratio ≈4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio >1, δCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio ≈6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The ¹⁴³Nd/¹⁴⁴Nd ratios or _ɛNd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to _ɛNd values. Terrigenous clay minerals of type I with the _ɛNd values of ™8 to ™6 originate mainly from North American fluvial deposits. Those of type II with the ε Nd values of ™9 to ™7 are mainly from the East Asia and North American fluvial deposits. Those of type III with ε Nd values of ™6 to ™3 could come from the central and eastern Pacific volcanic islands. Those of type IV with ε Nd values of ™13 to ™12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.     

Magnetic properties of sediments from the Pearl River Delta,South China: Paleoenvironmental implications

Magnetic parameters and their environmental implications of sediments in a core (PD) from the Pearl River Delta, South China, indicate that ferrimagnetic minerals with low coercivity, such as magnetite, dominate the magnetic properties although small amounts of Fe-sulphides occur. The fraction of Fe-sulphides increases and becomes the dominant minerals determining the magnetic characteristics in grey-black organic-rich clay horizons, indicating an anoxic, sulphate-reducing swamp environment resulting from a marine regression. In the "Huaban clay" , hard magnetic minerals, such as hematite and goethite, largely control the magnetic properties of the sediments and imply a long period of exposure and weathering. Where magnetite is the main magnetic mineral, its fraction and grain size determine properties such as magnetic susceptibility (κ ) and saturation isothermal remanent magnetization (SIRM). Ratios of SIRM/κ and χarm/SIRM reflect changes in sea level with high SIRM/κ and χarm/SIRM correlating with a smaller magnetic mineral grain size and rising sea level. Based on downcore variations of these environmental magnetic parameters along with sediment characteristics and microfauna, the sedimentary environment of the Pearl River Delta area can be divided into two main cycles of transgression and regression during the late Pleistocene and Holocene with more sub-cycles of sea level fluctuation during each transgression.     

On the relation of moderate-short term anomaly of earth resistivity to earthquake

IntroductionMany anomalies due to earthquake have been recorded in observation of earth-resistivity for30 years and over, which showed that there objectively existed the anomalies of each-resistivity.The crustal strUcture and medium conditions are quite complex, so the complexity of the temporal,spatial and intensive development of the anomalies is inevitable. Both of time and amplitUde ofanomalies among some stations near an epicenter are different (even among different observational directi…     

Relocation and seismogenic structure of the 1998 Zhangbei-Shangyi earthquake sequence

Introduction The January 10, 1998 Zhangbei-Shangyi, Hebei Province, earthquake has been the third large event of magnitude 6.0 and greater since the 1976 great Tangshan earthquake of magnitude 7.8 in the northern China (33皛42癗, 110皛124癊). Before this event, there were only two events of magnitude 6.0 and greater occurred in or around the Tangshan area since 1976: the M=6.9 Ninghe, Tianjin, earthquake of November 15, 1976 and the M=6.2 Hangu, Tianjin, earthquake of May 12, 1977. The …     

Two notes on the modern theory of inverse problems in geophysics

On the basis of comparison of the approaches to the solution of inverse problems in information theory and geophysics, it is shown that results, obtained in information theory, are suitable to supplement the theory of geophysical inverse problems. The conditions of the existence and uniqueness of the solutions of inverse problems in their practical discrete statement are specified. The terms of ɛ-entropy H _ɛ and informational capacity C _ɛ, characterizing “volumes” of unknown and observed data, are introduced. It is shown, that the instability of the solution of the inverse problem decreases with increase in H _ɛ, (increase in the “complexity” of studied section), if the relation H _ɛ ≤ C _ɛ is maintained.     

Terminal Ediacaran anoxia in deep-ocean: Trace element evidence from cherts of the Liuchapo Formation,South China

Here we report a detailed trace element study of the cherts from Liuchapo Formation, which is a terminal Ediacaran (551-542 Ma) succession in South China deposited in deep-water basinal setting. The REE of Liuchapo cherts shows similar features as observed for anoxic modern seawater (but not for hydrothermal fluids), characterized by positive La anomaly (La_N/Ce_N = 0.83–1.91, average 1.37), moderately negative Ce anomaly (0.53–1.1, average 0.73), positive Gd anomaly (average 1.08), positive Y anomaly (average 1.21), and depleted LREE and MREE. In addition, the Liuchapo cherts have low ΣREE (3.36–56.13 ppm, average 20.6 ppm), low Al₂O₃, Ti, Th and Zr concentrations, and high Y/Ho ratios (up to 43.9). The redox-sensitive trace elements concentrations in the cherts do not correlate with detrital input proxies. All of these features suggest that the redox-sensitive trace elements in the cherts were authigenically concentrated in water column and their concentrations thus are excellent indicators of ancient redox conditions. Very low Th/U ratios, high V/(V+Ni) and Fe_⊤/Al ratios, enrichments of redox-sensitive trace elements (U, V, Mo), and low concentration of Mn in the cherts imply anoxia in the deep seawater. Our data reveal that the terminal Ediacaran ocean was not completely oxidized and the deep ocean was still anoxic, at least in South China. We propose that although the oxidative events existed in the terminal Ediacaran oceans, decomposition of organic matter prolonged anoxia in the deep ocean. Supported by National Natural Science Foundation of China (Grants Nos. 40532012, 40873007, 40603021) and Chinese Academy of Sciences (Grant No. KZCX3-SW-141)     

Geochemistry and Sr-Nd isotope characteristics of tonalites in Zêtang, Tibet: New evidence for intra-Tethyan subduction

Tonalites from the island arc rock assemblage in the Zêtang segment of the Yarlung Zangbo suture zone were analyzed for major, trace elements (including REE) and Sr-Nd isotope. The experimental datademonstrate that the tonalites have the adakite-like characteristics, including high SiO2 (58%-63%),Al2O3 (18.4%-22.4%), Sr (810×10-6-940×10-6), Sr/Y (77-106), low HREE (Y=9×10-6-11×10-6, Yb=1×10-6-1.3×10-6), with LREE enrichment and faint Eu positive anomaly. Isr (0.70421-0.70487) is relatively low whereas 143Nd/144Nd (0.512896-0.512929) and εNd(t) values ( 6.7- 7.3) are high. These feainvolvement of a small amount of oceanic sediments. The identification of Z(e)tang adakites, derived from slab melting, presents new evidence for the intra-Tethyan subduction and the previous suggestion about the existence of intra-oceanic island arc within Tethys.     

Features and physical process of the dynamic evolution pattern of ground resistivity precursor front

ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅ１９６０′ｓ,ｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍｏｄｅｒｎｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙｈａｓｇｒａｄｕａｌｙｍａｄｅｉｔｐｏｓｉｂｌｅｔｏｐｒｅｄｉｃｔｅａｒｔｈｑｕａｋｅｓａｎｄｈａｓｐｒｏｍｏｔ...     

Occurrence of organochlorine pollutants in the eggs and dropping-amended soil of Antarctic large animals and its ecological significance

Persistent organochlorine pollutants (POPs) are analyzed for the dropping-amended soils from the habitats of Antarctic seabirds and seals in Fildes Peninsula and Ardley Island. The concentration ranges are 0.21 to 3.85 ng/g for polychlorinated biphenyls (ΣPCBs),0.09 to 2.01 ng/g for organochlorine pesticides (ΣDDT),and 0.06 to 0.76 ng/g for hexachlorocyclohexanes (HCHs). Among these,hepata-chlorobiphenyls,hexachlorobiphenyls,p,p′-DDE and α-HCH compounds are dominant. The concentra-tion ranges of ΣPCB,DDT and HCH in the eggs of skuas were 91.9―515.5 ng/g,56.6―304.4 ng/g and 0.5―2.0 ng/g respectively; those in the eggs of penguins were 0.4―0.9 ng/g,2.4―10.3 ng/g and 0.1― 0.4 ng/g; and those in the eggs of giant petrel were 38.1―81.7 ng/g,12.7―53.7 ng/g and 0.5―1.5 ng/g respectively. The dominant POP compounds in the eggs are PCB180,PCB153,p,p′-DDE and hexa-chlorobenzene (HCB). The present study shows that the concentration of POPs in the sea-bird-inhabited-dropping-amended soil varies with the extent of predation and nest occupancy of dif-ferent seabird populations. Statistical analysis on the POP concentrations from the different seabird eggs implies that the difference in the bio-concentration levels of the birds depends on the bio-habits of the species,such as the range of activity,distance of immigration,feeding pattern,and nest occupation. Among these,the most important factor is the location of the seabirds in the food chain and their feeding pattern. This shows that POPs accumulated in the seabirds resulted from the bio-concentration through the food chain. In addtion,210Pb dating for the dropping-amended soils (AD1-a and AD2) was performed,which provided the POP accumulation rate and the historic record for the soil profile. It indicates that POP will continuously affect the Antarctic ecosystem for a long time.     

Q P and Q S in Beijing and Jianchuan, Yunnan areas

Events from the December 1982 Huairou County, Beijing, and the July 1982 Jianchuan, Yunnan earthquake series were recorded at one station in Beijing City and at four stations in Eryuan area, Yunnan, respectively. Dividing the spectra (for P and S waves) from the smaller events in the series by spectra (for corresponding P and S waves) from the larger events in cach region, we have determined the high frequency source spectral decay rate to be ω⁻¹in both cases. Through trial and error method, we are able to determine the appropriate constantQ _P andQ _S that corrects the individual spectra to the proper high frequency decay rate. It is found that aQ _P of 800 and aQ _S of 550 can adequately compensate for the attenuation of the waves in Beijing area. For Jianchuan, Yunnan area the corresponding values are 900 and 400. This subject is supported by Chinese Joint Seismological Science Foundation.