胶东地区金矿床成矿时代及其成矿地球动力学背景-兼论壳幔相互作用与成岩成矿

Jiaodong Peninsula is the largest repository of gold in China. Varieties of studies have been involved in the mechanism of metallogenesis. This thesis is a part of the project "Study of basic geology related to the prespecting of the supra-large deposits" which supported by National Climbing Program of China to Prof. Zhou. One of the key scientific problems is to study the age and metallogenic dynamics of ore deposit and to understand how interaction between mantle and crust constrains on metallogenesis and lithogenesis. As Jiaodong Peninsula to be study area, the Rb-Sr, Sm-Nd and Pb isotopic systematics of pyrite and altered rocks are measured to define the age and origin of gold. The elemental and Sr-Nd-Pb isotopic compositions of dikes and granites was studied to implicate the source and lithogenesis of the dike and granite and removal of lithosphere and the interaction between mantle and crust in the Jiaodong Peninsula. Considering the tectonic of Jiaodong Peninsula, basic on the time and space, this thesis gives a metallogenic dynamics of gold mineralization and discusses the constraints of the interaction between mantle and crust on the metallogenesis and lithogenesis. This thesis reports the first direct Rb-Sr dating of pyrites and ores using sub-sampling from lode gold deposit in Linglong, Jiaodong Peninsula and the results demonstrate this as a useful geochronological technique for gold mineralization with poor age constraint. The Rb-Sr data of pyrites yields an isochron age of (121.6-122.7) Ma, whereas, those of ore and ore-pyrite spread in two ranges from 120.0 to 121.8 Ma and 110.0-111.7 Ma. Studies of characteristic of gold deposit, microscopy of pyrite and quartz indicate that the apparent ages of ore and ore-pyrite are not isochron ages, it was only mixed by two end members, i.e., the primitive hydrothermal fluids and wall rocks. However, the isochron age of pyrite samples constrains the age of gold mineralization, i.e., early Cretaceous, which is in good consistence with the published U-Pb ages of zircon by using the SHRIMP technique. The whole rock Rb-Sr isochron age of altered rocks indicates that the age of gold mineralizing in the Xincheng gold deposit is 116.6 ± 5.3 Ma. The Sr, Nd and Pb isotopic compositions of pyrite and altered rocks indicate that the gold and relevant elements were derived from multi-sources, i.e. dikes derived from enriched lithospheric mantle and granites, granodiorites and metamorphic rocks outcropped on the crust. It also shows that the hydrothermal fluids derived from mantle magma degassing had play an important role in the gold mineralizing. The major and trace elements, Sr-Nd-Pb isotopic data of granites and granodiorites suggest that the Linglong Granite and Kunyushan Granite were derived from partial melting of basement rocks in the Jiaodong Peninsula at post-collision of North China Craton with South China Craton. Guojialing Granodiorite was considered to be derived from a mixture source, that is, mixed by magmas derived from an enriched lithospheric mantle and crust during the delamination of lithosphere induced by the subduction of Izanagi Plate and the movement of Tancheng-Lujiang Fault. There are kinds of dikes occurred in the Jiaodong Peninsula, which are accompanying with gold mineralization in time and space. The dikes include gabrro, diabase, pyroxene diorite, gabrrophyre, granite-porphyry, and aplite. The whole rock K-Ar ages give two age intervals: 120-124 Ma for the dikes that erupted at the gold mineralizing stage, and <120 Ma of the dikes that intruded after gold mineralizing. According to the age and the relationship between the dikes and gold mineralizing, the dikes could be divided into two groups: Group I (t = 120-124 Ma) and Group II (t < 120Ma). Group I dikes show the high Mg and K, low Ti contents, negative Nb anomalies and positive Eu anomalies, high ~(87)Sr/~(86)Sr and negative εNd(t) values and an enrichment in light rare earth elements, large ion lithosphile elements and a depletion in high field strength elements. Thus the elemental and isotopic characteristics of the Group I dikes indicate that they were derived from an enriched lithospheric mantle perhaps formed by metasomatism of the melt derived from the recycled crustal materials during the deep subduction of continent. In contrast, the Group II dikes have high Ti, Mg and K contents, no negative Nb anomalies, high ~(87)Sr/~(86)Sr and positive or little negative εNd(t) values, which indicate the derivation from a source like OIB-source. The geochemical features also give the tectonic constraints of dikes, which show that Group I dikes were formed at continental arc setting, whereas Group II dikes were formed within plate background. Considering the tectonic setting of Jiaodong Peninsula during the period of gold mineralizing, the metallogenic dynamics was related to the subduction of Izanagi Plate, movement of Tancheng-Lujiang Fault and removal of lithopheric mantle during Late Mesozoic Era.

渭南地区末次冰期以来的蜗牛化石记录及古气候古环境研究

In this study, 172 mollusk assemblages from the Weinan loess section in the southeast of Loess Plateau, China, were identified quantitatively at relative high resolution. The results show: 1) the history and processes of paleoclimatic and paleoenvironmental changes in Weinan since the last 70 ka; 2) the characteristics of climatic changes during the period of the last glacial maximum (LGM); 3) the spatial pattern of paleoclimate variations at the south and middle parts of the Loess Plateau during the LGM period; 4) the timing of the last deglaciation and the return event of rapid climate change during the last deglaciation. The main conclusions are as follows: 1) 172 mollusk samples taken from the uppermost 9 m deposits cover the past 70 ka, which were sampled at the internals of 5 cm for S_0, 3 cm for L_(1-1) and L_(1-2), and 10 cm for L_(1-3), L_(1-4) and L_(1-5). Author analyzed quantitatively all individuals including broken pieces of snail shells, percentages of 15 species identified from 172 samples. Three main groups were determined according to the ecological requirement of each taxon. Based on the variations of three ecological groups and typical ecological species, The author intended to reconstruct the history of and processes of climate and environment since the last 70 ka in the Weinan region. The climate and environment in this region experienced the following changes: relative warm and humid stage from 67.5-20.3 cal. ka B.P., a period of forest-steppe or steppe developed; cold and arid stage from 20.3-15.5 cal. ka B.P., a dry steppe period, later wetter and colder; cold and humid period once time from 15.5 to 12.3 cal. ka B.P., a typical steppe or forest-steppe stage; cold and humid again from 12.3 cal. ka B.P. to 8.2 cal. ka B.P., a tropical steppe stage; warm and humid climate, a forest-steppe developed. 2) The climate during the period of the last glacial maximum (LGM) in Weinan was characterized by a general cold-humid condition, represented by occurrence of a number of the cool-humidiphilous mollusk species such as Gastocopta amigerella and Vallonia cf. pulchella in the section. 3) Comparison of the variations in abundance of Puncture orphana at Weinan with those at Luochuan and Changwu sections suggests that the summer monsoon intensity influenced differently at the three regions during the LGM period. The Weinan was weaker summer monsoon impact during all the period, the Luochuan was influenced occasionally, and Changwu was only a very short time affected, which indicated it might be located at the western margin of the summer monsoon influence during that period. 4) The ratio of thermo-humidiphilous mollusk group to cold-aridiphilous one shows an increase tendency at about 15 cal. ka B.P., reflecting the climate warming after the deglaciation in Weinan, which is approximately corresponding to the timing of warming period of the last deglaciation, found in the East Atlantic Ocean, the South China Sea and the Loess Plateau (indicated by the phytolith study). 5) A remarkable decrease in the number of thermo-humidiphilous and cool-humidiphilous mollusk species from 12.7 - 11.6 cal. ka B.P. indicates a cooling in climate and might be the reflection of the Younger Dryas event in Weinan. 6) Variations in the ratios of thermo-humidiphilous mollusk species to cold-aridiphilous ones reflect the climate instability in Holocene. There were four warm-humid periods (10-8.1 cal. ka B.P., 6.9-6.1 cal. ka B.P., 5.2-2.6cal. ka B.P., 1.6cal. ka B.P. to the present ) and three relative cold-arid periods (8.1-6.9 cal. ka B.P., 6.1-5.2 cal. ka B.P., 2.6-1.6 cal. ka B.P.), showing about a 1,000 year climatic oscillation.

温度、压力耦合背景下多相流体运移的数学模型研究

The Mathematical modeling of multiphase fluid flow is an important aspect of basin simulation, and also is a topic of geological frontier. Based on coupling relation of temperature, pressure and fluid flow, this dissertation discusses the modeling which conform to geological regularities of fluid migration. The modeling that is multi-field and multiphase includes heat transport equation, pressure evolvement equation, solution transport equation and fluid transport equation. The finite element method is effective numerical calculation methods. Author applies it to solve modeling and implements the finite element program, and the modeling is applied to Ying-Qiong Basin. The channels of fluid vertical migration are fault, fracture and other high penetrability area. In this thesis, parallel fracture model and columnar channel model have been discussed, and a characteristic time content and a characteristic space content been obtained to illustrate the influences of stratigraphic and hydrodynamic factors on the process. The elliptoid fracture model is established and its approximately solution in theory is gotten. Three kinds of modeling are applied to analyze the transient variation process of fluid pressure in the connected permeable formations. The elliptoid fracture model is the most similar geology model comparing with the other fracture models so the research on this fracture model can enhance the understanding to fluid pressure. In the non-hydrodynamic condition, because of the difference between water density and nature gas density, nature gas can migrate upon by float force. A one-dimension mathematical model of nature gas migration by float force is established and also applied to analyze the change in the saturation of gas. In the process of gas migration its saturation is non-continuous. Fluid flow is an important factor which influences the distribution of the temperature-field, the change of temperature can influence fluid property (including density, viscidity, and solubility),a nd the temperature field has coupling relations to the fluid pressure field. In this dissertation one-dimension and two-dimension thermal convection modeling is developed and also applied to analyze convective and conductive heat transfer. Author has established one-dimension and two-dimension mathematical modeling in which fluid is a mixture of water and nature gas based on the coupling relation between temperature and pressure, discussed mixture fluid convection heat transfer in different gas saturation, and analyzed overpressure form mechanism. Based on geothermal abnormity and pore pressure distribution in Dongfong 1-1, Yinggehai Basin, South China Sea, one-dimension mathematical modeling of coupling temperature and pressure is established. The modeling simulates the process that fluid migrates from deep to shallow and overpressure forms in shallow. When overpressure is so large that fractures appear and overpressure is released. As deep fluid flow to shallow, the high geothermal then forms in shallow. Based on the geological characteristics in Ya13-1, two-dimension mathematical modeling of coupling temperature and pressure is established. Fluid vertically flows in fault and then laterally migrates in reservoir. The modeling simulates the geothermal abnormity and pore pressure distribution in reservoir.

改造型盆地油气成藏机理与油气预测－以银根－额济纳旗盆地为例

Reformed basin is a basin that underwent multiple immense reformation after the sedimentary stage, the major geologic elements of the petroleum system in the prototyped basin are destroyed to a certain extent, and their petroleum system has been reconstructed. This type of basin is frequently found in the course of exploration both home and abroad. In China, especially in the western and southern part of China, the basins in which oil explorations have been conducted are mostly reformed basins. The reformed basins from Paleozoic, Late Mesozoic to Cenozoic are widely distributed in West and South China. They are, and moreover, will be a challenge for oil and gas exploration. The conventional investigation and exploration techniques used in the slightly reconstructed basin just don't work well when facing the reformed basin. Therefore, the study on the reformed basin, especially the study on the pool-forming mechanism and reservoir prediction becomes a focus and one of difficulties for the geologists overseas and domestic. Yingen-Ejinaqi Basin is a typical case of the Late Mesozoic and Cenozoic reformed basins in China. It locates in West China and is a exploration frontier with difficulties and no break through is made for years. A comprehensive research on it will be of significance for oil and gas exploration in similar basins of China. The late research for reformed basin in China now is mainly concentrated on basin classification, formation mechanism, geologic features, and survey technique, distribution regularity of oil accumulation and its dominating factors, assessment of oil exploration prospect and target zones, etc. On the other hand, the study on the pool-forming mechanism and reservoir prediction seems insufficient in systematization, and the research is deficient in methodology and combination of qualitative and quantitative studies, as well as the application of the new theory and techniques. The current efforts are mainly directed to structures (faults), sedimentation, the relationship between reservoir evolution and oil accumulation, and some other relevant fields. However, the application of the new theory and techniques seems to be insufficient such as petroleum system, pool-forming dynamics, fluid pressure compartment, and basin simulation, etc. So is the dynamic and integrated research. As a result, incomplete knowledge and understandings derived from the research on pool-forming mechanism and reservoir prediction often do not accord with rea-lity of the basin. The study and exploration under the guidance of this knowledge will inevitably lead to errors and failure. This paper, based on the previous study of the other geologists on reformed basins, with emphasis on "wholeness or systematic, dynamic and integrated" research, presents a reverse thinking of beginning from conserved units in the basin and the combination of qualitative and quantitative study with new theory and technique by building a geological model. The paper also puts forward a new thought for studying the oil & gas accumulation and reservoir prediction , and establishes a new research system for reformed basin. It is verified by the known reservoir and oil accumulation area in the basin and has a practical value for use and reference. The new ideas and achievements in this research are as following: 1.This is the first time that the system for studying the reformed basin and its pool-forming mechanism and reservoir prediction is presented. A reverse thinking and combination of qualitative & quantitative are applied here with emphasis on "wholeness or systematic, dynamic and integrated" research, new theory, techniques & methods comprehensive use and geologic models building. 2. Identifying criterion and methods, classifying schemes, and denominating principles for the conserved units of reformed basins are presented in this paper. The geologic model of conserved units of Yingen-Ejinaqi Basin has been built. It is a practical method when combined with the traditional way for basin survey and the conserved units study. 3.The dynamic sources of basin deformation are believed to be stress, gravity and thermodynamics. The stress and gravity are key factors in basin deformation and pool forming, especially stress. Scientific proof is provided by classifying the functional type, style and range of the stress, gravity and thermodynamics. 4.The pool forming and reservoir distribution of Yingen-Ejinaqi Basin are controlled by multiple factors or geologic conditions or/and co-controlled by both of them. The qualitative and quantitative research on petroleum system and basin modeling will help us understand and determine the pool-forming period of the conserved unit (timing), the oil migrating direction (orientation), the oil accumulating region (location), the oil distributing border (bordering) and the size of oil accumulation (quantification). Thus the pool-forming and distribution zones can be predicted. 5.Three generating modes (reform-succession type, reform-destroyed type and reform-regenerating type or reform-newborn type) of pool forming for reformed basins are presented here, together with the inner relationships between basin deformation type, overlapping style and pool-forming modes. The pool-forming modes are determined by deformation type and overlapping style. Reservoir distribution will be predicted based on the modes and other concrete pool-forming conditions. 6.The evaluation methods of the conserved units and zones and the parameter selection are reliable in optimal selecting of target zones. The technical terms, new ideas and methods for the study of reformed basins, the pool-forming mechanism and reservoir prediction are presented in this paper. The concepts and terms, the identifying criterion, the denominating principles, the generating modes for pool forming, the methods of reservoir prediction, and the evaluation techniques for conserved units and zones can be used for reference in studies on the petroleum exploration of reformed basins in China and abroad. It serves as a typical example for further research of the reformed basins and the geologic regulations of oil accumulation. It has a practical value of use and reference. The future research in the field of pool-forming mechanism of the reformed basins may well be on the process simulation of pool-forming dynamics of the reformed basins. Experimental work has been conducted to simulate the processes by using quantitative and qualitative methods combined. The further study in this field calls for more efforts.

南海北部大陆边缘盆地热演化史及其与油气关系

This thesis focuses on the present-day thermal field features, evolution and their connections to hydrocarbon generation of the three continental margin basins-the Yinggehai (Yingge Sea), Qiongdongnan(southeast Qiong), and Pear River Mouth basins-in northern South China Sea, based on available data from drillings, loggings, seismic cross-sections, BHTs, thermal indicators (Ro%, inclusion, etc) and geopressure measurements. After studying of present-day distribution of geothermal field and thermal disturbance of fluid in the sedimentary strata, the author discovered that the distribution of gas fields in Yinggehai Basin are closely related to the distribution of anomalously high thermal gradient area, whereas it is not the case for the Pear River Mouse Basin. And detailed processing of the fluid inclusion data indicates that geothermal fluids activated frequently in this area, and they may mainly be derived upward from the overpressure and hydrocarbon-generating beds, 3000-4500 m in depth. Therefore, the abnormal gradients in sedimentary beds were mainly caused by the active geothermal fluids related to hydrocarbon migrating and accumulating in this area. Because of the effect of overpressure retarding on vitrinite reflectance, the thermal indicators for thermal history reconstruction should be assessed before put into use. Although some factors, such as different types of kerogen, heating ratio, activities of thermal fluids and overpressure, may have effects on the vitrinite reflectance, under the circumstance that thermal fluids and overpressure co-exist, overpressure retarding is dominant. And the depth and correction method of overpressure retarding were also determined in this paper. On the basis of reviewing the methods of thermal history studies as well as existing problems, the author believes that the combination of thermal-indicator-inversion and tectono-thermal modeling is an effective method of the thermal history reconstruction for sedimentary basins. Also, a software BaTherMod for modeling thermal history of basins was successfully developed in this work. The Yinggehai Basin has been active since Tertiary, and this was obviously due to its tectonic position-the plate transition zone. Under the background of high thermal flow, long-term quick subsidence and fluid activities were the main reasons that lead to high temperature and overpressure in this basin. The Zhujiangkou Basin, a Tertiary fault-basin within the circum-Pacific tectonic realm, was tectonically controlled by the motion of the Pacific Plate and resembles the other petroliferous basins in eastern China. This basin developed early, and characterized intensive extension in the early stage and weak activity in the later stage of its development. Whereas the Qiongdongnan Basin was in a weak extension early and intensity of extension increased gradually. The relative geographical locations and the extensional histories of three basins ilustrate that the northern continental margin of South China Sea spread from south to north. On the other hand, the Qiongdongnan and Yinggehai Basins may have been controlled by the same tectonic regime since later Tertiary, whereas the Zhujiangkou Basin was not meaningfully influenced. So, the tectono-thermal evolution character of the Qiongdonnan basin should be closely to the other two. It may be concluded that the three basins have been developed within the active continental margin since Tertiary, and the local lithosphere might undergo intensive extension-perhaps two or three times of episodic extension occurred. Extension lead to large tectonoc subsidence and extreme thick Tertiary sediments for hydrocarbon generation in the basins. In response to the periodic extension of the basins, the palaeothermal flow were also periodical. The three basins all have the characteristics of multi-phase thermal evolutions that is good for oil-gas generation. And the overpressure expands the depth range of oil-gas habitat, which is meaningful to petroleum exploration in this region.

南海天然气水合物地热学研究

Through generalizing the thermal field characteristics in gas hydrates distribution area in the world, the favorable thermal conditions for gas hydrates in the South China Sea are analyzed firstly. On the basis of above analysis, focused on the gas hydrates stability zone (GHSZ), the dissertation initiated the gas hydrates studies with geothermal methods in the South China Sea which will provide useful information for gas hydrates resource exploration and evaluation in the future. On the basis of study on hydrates phase equilibrium and the GHSZ affecting factors, the potential planar distribution of gas hydrates is determined by studying the temperature and pressure conditions in the sea bottom with different water depth, and the thickness of GHSZ is attained by solving the hydrates phase boundary curve equation and geothermal gradient curve equation. The result shows that, if the chemical composition of hydrocarbons contains methane only and the salt content of water is 3.5%, hydrates can form and keep stable at sea bottom at water depth not less than 550m, and the thickness of GHSZ is more than 200m in Xisha Through, Southeastern area of Dongsha Islands, Southwestern basin of Taiwan Island, northern area of Nansha Trough. The GHSZ is thicker with heat flow, geothermal gradient, and thermal conductivity decreasing, and with water depth increasing. Geothermal field simulating also attains the base of GHSZ in Xisha through, which is less than the depth of BSR. Although the present T-P conditions is not the most favorable for gas hydrates through 6Ma history, gas hydrates are still profitable in Xisha Through, Southeastern area of Dongsha Islands, Southwestern basin of Taiwan Island, Luzon Trough and northern area of Nansha Trough by systemic study on the sedimentary and structural characteristics, the conditions of T-P and natural gas source, considering geochemical and geophysical indications found in the South China Sea.

内蒙古黄岗矿集区与锡矿化有关的花岗岩成因研究

Muanggang-Dajing area located in the south end of Dahinggan Mts is the only discovered tin-polymetallic minerzalization belt and the only tectonic magmaism zone with middle-upper grade tin-ore deposites in North China. Tin mineralization in this area is believed tn related to Yanshannian granites which is different from those in South China tin belt. Through geochemical study of these granites on the base of fieldworks , thin section observation, major and trace elements as well as isotopic composision determination, the isochronic sequence and petrogenetic series for the granites have been determined. Hi light ing on the petrogenesis of earlier Yanshannian of MOmarh granites, two groups granites with different Neodymium isotopic features have been distinguished. Both belonging to hi-K calc-alkalinic series, their nature of source rocks and.magma processing were restricted, we argue for that the two groups have get the isotopic differences from their sources-middle and later proterozoic juvenial crustal via mantle underplating. From then on , there is a pre-enrichment of tin in this area. The partial melting from a F rich soruses can dissolve and carry more tin from the same some due to the de-connection of melt, which supply the mineralization fluids after a thoroughly evolement.

亚洲地形和海陆分布变化对东亚环境格局形成演化的作用：数值模拟与地质记录对比

Earlier studies on the distribution of geological environmental indicators in China revealed drastic changes from a zonal climate pattern (planetary-wave-dominant pattern) in the Paleogene to a monsoon-dominant one in the Neogene, which suggested an inception of the initial East-Asian summer monsoon. However, there are different views about the time and causes of the changes.Here, we attempt to compile a series of paleoenvironmental maps based on newly collected climate indicators from the literatures and chronologically constrained evidence of geological maps in order to re-examine the temporal and spatial evolution of climate belts in China during the Cenozoic with special emphasis on the changes of the arid belt. These indicators include mammalian fauna, coal, carbonate concretions, jarosite, salt, gypsum deposits and pollen assemblages etc, with chronological controls that we believe reliable. Pollen assemblages and mammalian fauna have been classified into three categories (arid, semi-arid/sub-humid, humid) to reflect the intensity of aridity/humidity. Salt, jarosite and gypsum deposits are classified as the arid indicators. Carbonate concretions and coal are classified into the semi-arid/sub-humid and humid one respectively. Paleoenvironmental maps at 8 time slices have been reconstructed. They are the Paleocene, Eocene, Oligocene, Miocene, Early Miocene, Middle Miocene, Late Miocene and Pliocene.And furthermore, we attempt to use IAP^AGCM to simulate the evolution of climate belts in emphasizing on the changes of the rain band, and compare the results with the paleoenvironmental maps in order to examine the causes of the drastic paleoenvironmental changes near the Oligocene/Miocene boundary. 36 sensitive numerical experiments are carried out using the IAP__AGCM to analyze the impacts of the uplift of the Himalayan-Tibetan complex, shrinkage of the Paratethys Sea, expansion of the South China Sea and the development of the polar ice sheets on rain band in China.The main conclusions are as follows:The obtained results essentially confirm the earlier conclusions about a zonal climate pattern in the Paleogene and a different pattern in the Neogene, and illustrate that a monsoon-dominant environmental pattern with inland aridity formed by the Early Miocene, which is temporally consist with the onset of eolian deposits in China.Cenozoic cooling and the formation of polar ice sheets are unlikely the main causes to the changes of environmental patterns mentioned above in China. But northern hemispheric cooling and the ice-sheets can intensify the Siberian High Pressure, and strengthen the winter monsoon circulations and enhance the aridity in the west part of China. These results support the earlier studies.Shrinkage of the Paratethys Sea and uplift of the Himalayan-Tibetan complex played important roles in strengthening the East Asian monsoon and induceing the above changes of environmental pattern, which is consistent with the earlier studies. Furthermore, "the monsoon-dominant pattern" appears when the Himalayan-Tibetan complex reaches to about 1000-2000 meters high and the Paratethys Sea retreats to the Turan Plate.4) Expansion of the South China Sea is another significant factor that drives the evolution of environmental patterns. We believe that the above three factors co-act and drive the change of the environmental patterns from a planetary-wave-dominant one to a monsoon-dominant one. However, the impacts of each factor vary by regions. The uplift mainly increases the humidity in Southwestern China and the aridity in northwestern country. The shrinkage mainly increases the humidity in Northern China and also enhances the aridity in the northwestern country. The expansion greatly increases the humidity in the south part of China.

句容海安区块热史、成烃史与二次生烃

Jurong -Hai'an block of lower Yangtz area is one of the important petroleum exploration area among the residual marine basins in the south China. In the history of the basin's evolution, the strongly compressing, napping, folding and deforming during Indosinian to Yanshan epoch resulted in destruction of the early formed petroleum pool. Therefore, the strategy exploration of the secondary hydrocarbon generation and later formation of petroleum pool was brought forward for petroleum exploration and planning in the study area..On the basis of tectonic and sedimentary as well as present-day thermal regime evolution, using vitrinite reflectance and apatite fission track data and the paleo-heat flow based method, the basin's thermal history is reconstructed and hence the strata's temperature history are obtained. In addition, the maturation histories of the main four sets of marine hydrocarbon source rocks in the block are calculated. Furthermore, taking the maturity in the end of early Cretaceous as the original maturity and according to the formulas fitted by the secondary hydrocarbon generation model, the secondary hydrocarbon generation potential of the four sets of source rock is evaluated.The results of thermal history reconstruction show that Jurong-Hai'an block was under an uniform thermal setting during the Caledonian to Hercynian period and characterized by middle heat flow (52~57rnW/ m2). The uniform thermal setting was divided during and after Indosinian to Yanshan epoch. Wuwei area of southern Anhui province was under the high heat flow setting(~90 mW/m2)between 236Ma and 137Ma; Jurong area of southern Jiangsu ,Huangqiao area and Subei basin reached its maximum heat flow of 90,84 and 78-82 mW/m2 at 101Ma,157Ma and 56Ma respectivelyThe study of secondary hydrocarbon generation shows that the upper Paleozoic and Triassic source rocks have excellent secondary hydrocarbon generation potential. Silurian source rock posses some secondary hydrocarbon generation. Cambrian source rock, however, nearly has no secondary hydrocarbon generation. Overall there are no advantages of secondary hydrocarbon generation in the southern area of Jiansu. The intensity of secondary hydrocarbon generation in North Jiangsu basin is definitely better than that in the southern area of Jiangsu.

Mantle-derived gaseous components in ore-forming fluids of the Xiangshan uranium

The Xiangshan U deposit, the largest hydrothermal U deposit in China, is hosted in late Jurassic felsic volcanic rocks although the U mineralization post dates the volcanics by at least 20 Ma. The mineralization coincides with intrusion of local mantle-derived mafic dykes formed during Cretaceous crustal extension in South China. Ore-forming fluids are rich in CO2, and U in the fluid is thought to have been dissolved in the form of UO2 (CO3)22− and UO2 (CO3) 34− complexes. This paper provides He and Ar isotope data of fluid inclusions in pyrites and C isotope data of calcites associated with U mineralization (pitchblende) in the Xiangshan U deposit. He isotopic compositions range between 0.1 and 2.0Ra (where Ra is the 3He/4He ratio of air=1.39×10−6) and correlates with 40Ar/36Ar; although there is potential for significant 3He production via 6Li(n,α)3H(β)3He reactions in a U deposit (due to abundant neutrons), nucleogenic production cannot account for either the 3He concentration in these fluids, nor the correlations between He and Ar isotopic compositions. It is more likely that the high 3He/4He ratios represent trapped mantle-derived gases. A mantle origin for the volatiles of Xiangshan is consistent with the δ13C values of calcites, which vary from −3.5‰ to −7.7‰, overlapping the range of mantle CO2. The He, Ar and CO2 characteristics of the ore-forming fluids responsible for the deposit are consistent with mixing between 3He- and CO2-rich mantle-derived fluids and CO2-poor meteoric fluids. These fluids were likely produced during Cretaceous extension and dyke intrusion which permitted mantle-derived CO2 to migrate upward and remobilize U from the acid volcanic source rocks, resulting in the formation of the U deposit. Subsequent decay of U within the fluid inclusions has reduced the 3He/4He ratio, and variations in U/3He result in the range in 3He/4He observed with U/3He ratios in the range 5–17×103 likely corresponding to U concentrations in the fluids b0.2 ppm.

湖光岩玛珥湖沉积物硅藻硅同位素研究

本论文选取我国的典型玛珥湖－湖光岩玛珥湖为研究对象，在国内外率先系统开展湖泊沉积物硅藻硅同位素研究。为获取过去2000a来的气候环境记录，对原有沉积物-水界面采样装置进行了改进，将沉积物柱芯无扰动采集深度从60cm提高到150cm。建立了一套有效的五阶段硅藻提纯方法，成功从初始硅藻含量大于7%的沉积物中提取出纯度达90％以上的硅藻样品，为广泛开展沉积物硅藻硅氧同位素研究奠定了基础。放射性核素Pb-210、Cs-137、C-14计年结果表明，该湖沉积物堆积速率稳定，具连续、稳定的堆积特点，是气候和环境变化的良好记录体。湖光岩玛珥湖沉积物硅藻硅同位素记录了硅藻利用水体溶解硅的比例变化。沉积物硅藻硅同位素与生物硅含量的变化关系为揭示湖泊古环境提供了重要线索。当硅藻硅同位素组成与生物硅含量呈正相关变化时，湖水溶解硅利用比例主要受温度控制，硅藻硅同位素可反映古温度变化。当硅藻硅同位素组成与生物硅含量不呈相似变化时，湖水溶解硅利用比例主要受有效养分控制，沉积物硅藻硅同位素仅仅反映硅藻利用水体溶解硅的比例，不反映古温度变化。湖光岩玛珥湖沉积物柱芯硅藻硅同位素组成的变化范围为 -0.6‰～1.1‰，其最小值出现于1580～1920年间，指示了1580～1920年为湖光岩地区过去2000年来最冷的时期，为中国南方热带地区现代小冰期的存在提供了新的证据。

华南下寒武统层序框架的初步构建―以遵义松林地区为例

华南下寒武统保存着国际著名的生物群（如澄江生物群），同时蕴藏着磷块岩、重晶石、稀土及Ni-Mo-PGE等丰富的矿产资源，因此，它一直为地质科学家们持续关注的热点之一。关于华南下寒武统的研究，前人在古生物学方面已经取得了卓著的成就，主要表现在国际权威期刊上（如期刊《Science》和《Nature》）已发表大量的关于澄江生物群的研究成果，对早期生命演化研究具有重要而广泛的影响。然而，华南下寒武统年代学及国际对比研究方面已明显滞后，公开发表的华南下寒武统的高精度、可靠的锆石U-Pb年龄数据至本研究论文截稿时止仍然仅有唯一的一个，即Jenkins et al. (2002)报道的国际前寒武系-寒武系界线层型候选剖面―云南晋宁梅树村剖面的朱家菁组中谊村段中部（第5层）钾质斑脱岩锆石SHRIMP U-Pb年龄（538.2 ± 1.5 Ma）。因而，华南下寒武统中的重要生物群、矿床及具全球对比意义的C同位素漂移事件缺乏地层精确年龄的约束，进而制约了早期生命演化理论、矿床成因解释及地层国际对比等方面研究的发展。 近来，发现华南下寒武统赋存独特的钾质斑脱岩层，它们在横向上广泛分布于云南东部、四川峨眉麦地坪、贵州西部（如织金和金沙岩孔）及北部（如遵义松林）、湖北宜昌泰山庙和湖南张家界等地区，在地层序列垂向上主要产出于朱家菁组中谊村段中部、石岩头组底部以及它们的相当层位。这些钾质斑脱岩既是建立地层框架等时层潜在的物质基础，亦是获取地层精确锆石U-Pb年龄的具重要意义的研究对象之一。因此，对它们进行系统研究可望改观华南下寒武统年代学及国际对比研究方面的落后现状。 同时，华南下寒武统广泛产出的磷块岩既具有重要的资源价值，另一方面，任一磷块岩层代表着一次独立的成磷事件，因而将华南地区下寒武统磷块岩进行区域上的对比研究，从而以磷块岩层作为等时层，对构建华南下寒武统地层框架具有重要的地层学意义。 此外，华南下寒武统产出的Ni-Mo多元素富集层广泛分布于扬子地台范围，西起云南东部，东部延至浙江诸暨地区，在NE-SW向延伸近1600 km，它既代 表了重要的成矿事件，亦为关键的地球化学异常层位。因此，对Ni-Mo多元素富集层进行区域上的对比研究，明确它在华南下寒武统各重要剖面的产出位置，对于构建华南下寒武统层序框架具有重要意义。 遵义松林地区的下寒武统因赋存Ni-Mo-PGE矿床及与滇东地区澄江生物群相当的遵义生物群而日益受到国内外地质学家们的广泛关注。该区牛蹄塘组底部产出磷块岩、钾质斑脱岩及Ni-Mo多元素富集层，与滇东地区梅树村剖面出露的地层具有潜在的可对比性。因此，本研究选取近年来日益受科学家们关注的遵义松林地区下寒武统作为研究对象，重点对该区牛蹄塘组底部的钾质斑脱岩开展矿物学、地球化学和年代学研究。同时，将遵义松林地区下寒武统剖面上磷块岩、钾质斑脱岩、Ni-Mo多元素富集层主要与滇东地区梅树村剖面的相应岩层进行地球化学对比研究。研究的目的在于通过对华南地区上述两条代表性的下寒武统剖面进行地层对比研究，初步构建华南下寒武统具时间、空间涵义的层序框架，从而约束华南下寒武统中的重要生物群、矿床及具全球对比意义的C同位素漂移事件的时间，进一步促进华南下寒武统的划分和全球对比。论文获得以下主要结论性认识： （1）滇东地区朱家菁组中谊村段中部钾质斑脱岩及其邻近的磷块岩可构成华南下寒武统层序框架的第一个标志层。这一标志层在贵州大部分地区（或华南地区的多数下寒武统剖面）缺失。该标志层的磷块岩稀土元素总量和Y含量高于新元古代陡山沱期磷块岩，低于遵义松林地区牛蹄塘组底部及其华南其它地区相当层位（石岩头组底部及戈仲伍组）的磷块岩。第一个标志层的钾质斑脱岩的原始岩浆为亚碱性系列的酸性岩浆，其典型特征为具有较低的Zr（变化范围144×10-6~291×10-6，平均196.4×10-6）、Nb（变化范围10×10-6~13×10-6，平均11.86×10-6）含量和较高的Zr/Nb比值（变化范围为12.63~24.24，平均值为16.55）。这一层钾质斑脱岩的锆石U-Pb年龄为538.2±1.5 Ma（Jenkins et al., 2002）。 （2）遵义松林地区牛蹄塘组底部钾质斑脱岩和磷块岩分别相当于滇东地区石岩头组底部钾质斑脱岩和磷块岩，它们构成华南下寒武统层序框架的第二个标志层。该标志层中钾质斑脱岩的原始岩浆性质为中性岩浆，其碱性程度高于朱家菁组中谊村段中部钾质斑脱岩的原始岩浆。相对于中谊村段中部钾质斑脱岩，该层位的钾质斑脱岩具有高的Zr(变化范围187.0910-6~391.5710-6，平均值318.4010-6)、Nb（49.6910-6~140.0010-6，平均值90.6810-6）含量和低的Zr/Nb（2.60~4.32，平均值3.61）比值。该钾质斑脱岩的年龄为518 ± 5 Ma。该标志层的磷块岩以极其富REE和Y为特征，其稀土元素总量平均值为636.01×10-6，Y含量平均值262.43×10-6，明显高于滇东地区中谊村段磷块岩（∑REE平均值为195.45×10-6，Y含量平均值为91.2310-6），它们代表早寒武世时期一次特殊的以极其富REE和Y为特征的成磷事件。 （3）Ni-Mo多元素富集层可以作为构建华南下寒武统层序框架中的第三个等时标志层。滇东地区梅树村剖面的Ni-Mo多元素富集层被重新校正在玉案山组底部（即13层，Ni、Mo含量分别为135×10-6和583×10-6）。Ni-Mo多元素地球化学标志层的典型特征为在剖面上具Ni、Mo等多种微量元素及贵金属元素的最高异常。该标志层的Re-Os年龄为537~542 Ma，可能代表的不是地层层序的年龄。 （4）初步建立华南下寒武统时间框架。约束了华南地区下寒武统Ni-Mo-PGE矿床的下限年龄应为518 ± 5 Ma。同时，该时间框架亦约束了滇东地区澄江生物群及最古老三叶虫的下限年龄（518 ± 5 Ma），考虑到石岩头组底部钾质斑脱岩的产出位置与玉案山组中部澄江生物群的产出层位存在相当的距离（大于80 m），因此，前人对澄江生物群的推测年龄（525~530 Ma）可能有些偏老。此外，初步约束了华南地区具全球对比意义的C同位素正漂移事件的年龄（538~518 Ma）。该时间框架是建立在两个相互支持的地层高精度锆石SHRIMP U-Pb年龄的基础之上，而国际前寒武系-寒武系界线年龄的最新研究成果为542 Ma，因此，它支持将华南地区的前寒武系-寒武系界线置于朱家菁组中谊村段中部钾质斑脱岩层（第5层）的下伏地层的方案。结合华南地区最新的地层古生物学研究成果（朱茂炎等，2001；Zhu et al., 2003），将这一界线置于朱家菁组中谊村段底界可作为一种合理的选择。

中国南北方泥盆纪腕足化石碳、氧、锶同位素研究

海相碳酸盐岩C、O、Sr 同位素研究是地球化学重要的示踪手段之一。它可以为认识地质历史时期的气候变化，海水原始碳、氧、锶同位素组成，陆地和海洋生物盛衰的长期变化特征，以及碳、氧等元素的外生循环等一些重大的基础学科问题提供重要的依据。研究表明：腕足化石因具有较强抵抗成岩后生作用能力、分布广泛、便于操作等原因被认为是较为理想的研究样品之一。 本论文对来自中国南、北方泥盆纪不同沉积单元腕足化石碳、氧、锶同位素组成进行测试，探讨中国南、北方不同沉积单元腕足化石碳、氧、锶同位素差异。从地球化学角度对我国泥盆纪海平面变化，海洋生物盛衰、陆地风化强度以及构造运动研究进行诠释。 中国泥盆系沉积类型齐全，从南到北，分布着不同构造单元条件下沉积而成的地层。华南泥盆系属地台型稳定沉积类型，四川龙门山地区泥盆系形成于冒地槽构造单元中，而中国北方泥盆系为优地槽活动构造单元的产物。三类构造单元的地壳活动和火山活动不同，生活在其中的腕足壳体碳、氧、锶同位素组成是否存在差异？不同构造单元的海平面变化、海洋生物盛衰以及陆地风化强度是否不同。 研究中通过上述不同沉积单元腕足化石碳、氧、锶同位素组成详细研究，得出以下几点认识： 1) 在腕足化石保存鉴定过程中：微体结构实验显示南、北方剖面腕足化石壳体结构保存完整，有着明显的纤维层和棱柱层结构，但北方剖面腕足化石微裂隙较多，有着不少后期物质充填。在阴极灯照射下，南方剖面腕足化石基本不发光，仅因少量裂隙中后期物质充填有着微弱发光现象存在。北方剖面腕足化石基本上都有着轻微发光现象，尤其内蒙古地区腕足化石。微量元素Fe、Mn、Sr 含量及其Mn/Sr 值表明南、北方剖面腕足化石绝大多数符合腕足保存完好的标准。表明：南方剖面腕足化石保存完好，可以用于的碳、氧、锶同位素组成研究。北方剖面腕足化石保存程度较差，其同位素信息可能遭受成岩蚀变作用的影响，特别是容易遭受蚀变影响的氧同位素组成。 2) 成岩后生作用总是导致碳酸盐岩全岩样品中碳、氧、锶同位素组成发生变化，无法保存原始的同位素信息。腕足化石同碳酸盐岩全岩碳、氧、锶同位素对比表明：碳酸盐岩全岩样品中碳、氧同位素组成都低于腕足化石样品中同位素组成，锶同位素组成正好相反，但在不涉及定量化研究的前提下，碳、锶同位素基本上可以代表着地质历史时期碳、锶同位素变化趋势。也即是说可以利用碳酸盐岩全岩样品进行碳、锶同位素演化趋势研究。至于碳酸盐岩全岩样品中氧同位素组成，低于腕足化石氧同位素组成达 -2‰～-3‰。在目前常用于氧同位素古温度的研究中差异太大。因此，建议不要利用碳酸盐岩全岩样品中氧同位素组成进行古温度研究。 3) 碳同位素组成变化可以指示有机碳的埋藏情况。中国南、北方剖面腕足化石碳同位素研究表明：腕足化石中碳同位素组成基本上在 -2‰ ～ 4‰之间变化，北方剖面较低，南方剖面较高。其碳同位素Locfit 演化对比显示：北方剖面碳同位素演化同华南以及四川龙门山剖面中碳同位素演化有着许多相似之处，表明北方海域有机碳埋藏情况同南方海域有机碳埋藏情形基本一致。分析表明：四川龙门山以及华南剖面泥盆纪时期有着三次有机碳高速埋藏时期，可能受海平面变化以及与之有关的生物繁盛状况共同控制。至于北方剖面碳同位素组成相对较低，一方面可能由于腕足化石保存方面的原因，在成岩蚀变作用影响下北方剖面腕足碳同位素组成较低。另一方面，北方地区较多的火山活动，释放大量含有较多12C 的CO2，融入海水发生同位素交换，导致北方地区碳同位素组成较低。 4) 由于北方剖面存在遭受成岩蚀变作用影响的可能，北方剖面腕足化石壳体氧同位素平均组成(-11.75‰ ~ -21.13‰)明显低于四川龙门山剖面(-5.14‰ ~-7.20‰)、华南剖面(-4.35‰ ~ -10.31‰)氧同位素平均组成，无法对水岩反应控制海洋中氧同位素组成给出肯定的答案。但腕足化石保存完好的四川龙门山剖面和华南剖面氧同位素组成(氧同位素素组成埃姆斯阶为-7.20‰、-7.58‰；吉维特阶-5.62‰、-4.60‰；氟拉斯阶-5.18‰、-4.35‰)显示：优地槽沉积单元的龙门山海域同稳定地台沉积单元的华南海域氧同位素一致，甚至较低，表明水岩反应根本无法控制海洋中氧同位素组成。 5) 四川龙门山剖面下泥盆统埃姆斯阶氧同位素组成为 -9.9‰～-4.5‰，明显低于世界上其他地区同时期腕足化石的氧同位素组成，其差异达 -3‰~-4‰。微量元素Fe、Mn 的演化趋势以及氧同位素演化趋势显示：龙门山海域在埃姆斯阶时期同广阔海域之间海水交流不畅通，其氧同位素组成受淡水河流注入的影响。根据氧同位素古温度计估算(假定古海水δ18O 值为 -3‰SMOW)，姆斯阶时期温度高达52℃，远远超过生物所能生存的极限，印证龙门山海域埃姆斯阶氧同位素组成受淡水河流注入的影响。艾菲尔阶～氟拉斯阶，龙门山海域的温度为21℃ ～33℃，表明龙门山海域为典型的低纬地区热带气候。 6) 早泥盆纪时期，锶同位素比值较高，显示风化作用较为强烈；可能是由于加里东造山作用的影响，大量陆地的暴露，促进风化作用的进行。其后，锶同位素组成逐渐降低指示风化作用变弱。锶同位素降低可能由于海底扩展运动造成幔源锶的增加，同时引起海平面上升，引起陆地风化面积的减少，导致风化作用的减弱。幔源锶增加和陆源锶的减少，造成锶同位素比值的不断下降。早泥盆世晚期－中泥盆世，锶同位素组成显示风化作用(强度较低)和构造运动稳定。可能原因为在海平面较高时海侵－海退幅度较小，幔源锶和陆源锶之间达到均衡。中泥盆世后期，锶同位素组成显示：风化作用程度较强。可能由于该时期温度的缓慢上升，导致风化作用加强，陆源锶输入增多引起的。 7) 不同沉积单元腕足化石碳、氧、锶同位素对比表明：局部的区域环境对碳、氧、锶同位素有影响。在考虑利用不同剖面进行地质历史时期某时段碳、氧、锶同位素数据叠加构建完整同位素演化曲线时；对于碳同位素，相同沉积单元条件下，辨别出长时间变化和局部影响时可以应用于同位素演化曲线的构建。而不同沉积单元的碳同位素组成存在差异，不能应用于碳同位素曲线的构建。不同沉积单元氧同位素组成存在较大差异，相同沉积单元的氧同位素组成同样也存在较大差别，表明局部环境对氧同位素组成影响较大，氧同位素曲线的构建最好避免多个剖面的叠加。锶同位素比值，不同沉积单元在长期演化趋势上基本一致，在排除局部环境因素的影响下可以进行多剖面锶同位素演化曲线的构建。

南海ODP1144也微玻璃陨石物理地球化学特征及成因和气候效应综合研究

澳大利亚-东南亚散落区覆盖着地球表面的1／10，是迄今散落面积最大，最年轻，成分最复杂的散落区。澳一亚群微玻璃陨石已经在印度洋、太平洋西部、Sulu海、Celebes海和菲律宾海的40个深海岩心中被发现。澳-亚（微）玻璃陨石及撞击残骸的分布区域以Indochina为中心呈放射状或者稍微同心状分布模式，因而许多研究者认为Indochin。是澳亚群的撞击坑所在地。南海是西太平洋最大的边缘海之一，地处太平洋板块、印度洋板块及欧亚板块的接合部位，具有典型的边缘海特点—对古海洋学变化具有放大作用，南海的北部陆缘保存有完好的晚更新世地层，记录着丰富的海洋地质和古环境演化的信息。同时南海在澳大利亚-东南亚散落区范围内，距离假定Indochina的撞击位置〔12°N，106°E）较近，对于澳亚群微玻璃陨石的研究具有重要的地理优越性。南海海域澳亚群（微）玻璃陨石事件现今研究较少，对于南海含微玻璃陨石孔位的综合研究是近年来的热点和重点。南海ODPI144孔位于20°3.18'N，117'25.14'E，取得了1.1Ma以来连续的沉积地层样品，沉积物中含有丰富的微玻璃陨石，对含有微玻璃陨石层位加密取样，取样间距为1一Zcm。微玻璃陨石主要赋存在386.17-386.27mcd（合成深度米数：meter of composed depth，以下简称m），样品中共挑出完整的微玻璃陨石969颗，不规则碎片1543颗，在柱样状386.23m处微玻璃陨石的含量最为丰富，共发现完整颗粒194颗，不规则碎片239颗。同时在微玻璃陨石的挑选的基础上，对孔位中有孔虫进行了初步研究，挑选出其中的优势种属袋拟抱球虫或者红拟抱球虫。本文通过对南海ODPll44孔微玻璃陨石赋存层位、物理性质、地球化学特征等综合研究，结合有孔虫碳氧同位素研究结果进行分析，本文研究主要取得了以下几点认识：前人对于澳亚群微玻璃陨石的分类问题，根据物理性质和地球化学特征，划分了两种类型的微玻璃陨石，即普通型和瓶绿色微玻璃陨石，对于南海ODPI144孔微玻璃陨石物理性质和化学特征的综合研究，表明了南海沉积物中的微玻璃陨石为澳亚群普通型微玻璃陨石。根据微玻璃陨石表面特征，可能微玻璃陨石在沉积过程中受到了一定的溶蚀作用，但是其空气动力学过程目前仍不清楚。通过微玻璃陨石的物理性质、主量元素特征以及微量元素特征研究，表明微玻璃陨石的主要成因是部分熔融作用的产物，与闪电熔岩和撞击玻璃具有非常明显的类似特征，对于南海ODP1144孔微玻璃陨石的主量元素、微量元素及稀土元素等地球化学特征的综合研究，表明微玻璃陨石母岩为地球岩石，尤其是与上地壳沉积岩石类型密切相关。微玻璃陨石是由两种或者两种以上的母源物质混合而成的。地球化学特征表明：ODPll44孔及整个澳亚群普通型微玻璃陨石的原始母源物质可能是一些很年轻的（未遭受淋滤作用）碎屑沉积岩，另一种母源成份可能是粘土或者杂砂岩。这两种结果仅仅是靶区母源物质的两种成份，可能还存在其它成份，例如白云石成份的出现，这些结果从一个侧面同样反映了澳亚散落区微玻璃陨石母源物质的成份复杂性。通过ODP1144孔微玻璃陨石的研究，结合南海和澳亚群其它孔位的资料对比，发现在南海及一些等高分辨率岩心中的微玻璃陨石的赋存层位主要在B/M之下，而其它地区的低分辨率孔位则位于界线层或者之上。其原因可能是沉积过程中生物扰动和沉积地磁的获得深度（PDRM）影响了微玻璃陨石和B/M界线的位置。生物扰动对微玻璃陨石的影响最高可达8cm，沉积速率强烈的影响PDRM获得深度。沉积速率较低的孔位，其PDRM的值异常的高，而沉积速率较高的孔位，PDRM深度平均约为16cm。生物扰动以及 PDRM的获得深度影响了微玻璃陨石和地磁事件地层位置，上述原因直接导致了微玻璃陨石沉积年龄探讨的复杂性。根据本文的研究结果和综合资料对比，澳亚群微玻璃陨石的撞击地点可能存在着很大的不确定性，对南海ODP1144孔微玻璃陨石研究表明，其源坑位置距离现今预测Indochina的位置向东北方向偏移，偏移的程度还需要南海更多的孔位的研究结果，坑的半径大小可能在50-140km之间，靠近我国南方的东南亚地区应该是撞击地点的最可能区域。南海ODP1144孔有孔虫碳氧同位素研究结果表明，澳亚群微玻璃陨石事件对于南海地区存在着一定的气候效应，在该时期，由于撞击事件的发生，导致了该区有一次短暂的气候变冷事件，气温约下降了4℃，持续的事件约2ka。这一证据表明了澳亚微玻璃陨石事件对于南海的气候具有显著的影响。根据上述所取得的认识，结合当前微玻璃陨石的研究现状，本文提出我国南方包括南海应该是今后澳亚群微玻璃陨石的重点地区，应该加强对该区域的综合研究程度，在该区进一步寻找增加南海中含微玻璃陨石赋存层的孔位资料。通过本文的对南海ODPI144孔微玻璃陨石的类型、成因以及撞击事件的气候效应探讨，这些成果对于今后在该区域的研究甚至整个澳亚群的研究都起到了一定推动作用，为今后的研究工作提供了一个全新的思路。

扬子地台晚震旦至早寒武世沉积碳同位素研究

震旦-寒武交变期是地史上一个重大转折期，从隐生宙向显生宙过渡，海、陆、空发生了显著不同的变化，是一个具有特殊意义的过渡时期。中国扬子地区广泛发育的海相沉积层序有效地记录了震旦一寒武交变期重要的地质事件，因此为研究该时期大气圈、生物圈、岩石圈和水圈的相互联系提供了独一无二的场所。在前寒武纪一寒武纪地质研究中，由于缺少标志性生物化石，行之有效的生物地层学方法在上前寒武系的划分和对比中受到很大限制，沉积有机，质干酪根和相应碳酸盐的稳定碳同位素分析已经成为全球对比和划分的一个极为重要的的研究方法。尽管一些学者对扬子地台进行了多年的地球化学研究，使用碳酸盐和与之共生的有机质碳同位素组成对广泛的扬子地台变化的沉积环境进行研究还很欠缺、对分析和探讨该时期的生命演化过程和环境变化的关系研究方面还不足。本研究是以中国扬子地区为研究范围，用沉积碳酸盐和与之共生的有机质碳同位素组成对广泛的扬子地台变化的沉积环境（台地相、盆地相、过渡地带）进行分析，初步建立了一个地球化学模型，用于解释震旦一寒武交变期沉积地球化学记录，分析和探讨区域扬子地台碳循环和环境变化与地质事件之间的内在和外在联系：（1）南沱期：有机碳同位素组成（瓮安剖面平均值在-35.0‰左右）表现为较强负异常。地球被称为雪球（Snow-ball）或部分冰雪覆盖球体（Slush-ball），水体滞留和水动力不强，原始产率较低，物源以深源为主；生物不发育，主要是细菌和低等的真核细胞生物；空气和海水的气体通过冰裂缝进行交换，促进了碳酸盐的溶解；有机碳循环主要通过厌氧过程，比如细菌硫酸盐还原作用进行。（2）陡山沱期和灯影期：南沱晚期一陡山沱早期，海水的碳酸盐碳同位素组成短期仍然较负（瓮安剖面的δl3Ccarb-avg为-2.8‰ 松桃剖面1、2的δ13Ccarb-avg分别是-3.5％0和-8.6％。）；有机质的碳同位素组成总体呈现正漂移（瓮安护3Corg－avg：-26.3‰；南明剖面的δ13Corg-avg高达-26.7‰），这正是全球分布的“帽”碳酸盐出现的时期：接近地表的火山去气作用释放出较之现代350倍的CO2，导致地球迅速变暖，冰雪融化，大陆风化作用加强，海平面上升，“雪球，，转化为“温室，大气中大量的CO2快速转化为碳酸钙沉入海水中。全球可能处于一个异常高的海洋沉积速率时期。随后陡山沱组的护3Ccarb值显著上升，暗示了这一时期生物作用加强，有机碳埋藏速率明显提高，有机碳和还原硫埋藏的增加，导致上层海水345的富集，硫同位素组成较高。热液作用和上升洋流作用促成了瓮安磷矿的形成和瓮安生物群的繁盛。在南沱冰期后的陡山沱期和灯影期，高的别3c的出现主要是由于进行光合作用的海洋植物群体产率的迅速增加、海洋沉积速率的升高、海洋深部水柱中缺氧层的存在、热液活动、上升洋流作用、海水分层结构引起的，而短期同位素组成的负漂移和生物产率的变化则可能是区域事件所造成。明显的碳同位素组成负漂移出现在前寒武／寒武界线附近，这反映了碳短期变化的翻覆，与震旦纪末生物绝灭、环境变化的地质事件相符合。（3）牛蹄塘期：本研究结果发现，在牛蹄塘组／郭家坝组底部黑色岩系中，有机碳、无机碳、有机硫、黄铁矿硫同位素组成值相对较低，有机碳和黄铁矿含量相对较高。δ3Corg-avg和δ3Ccarb-avg分别是-33.9士0.7‰和-2.5＝0.4‰；TOC＞0.5；黄铁矿平均含量为0.96％间变化；黄铁矿（δ4ScRs）和有机硫同位素组成（δ34SOBS）平均值分别为0.3士7.5‰和3.4土7.1‰。由于牛蹄塘初期的环境变化频繁和不稳定，扬子区处于一段特殊的时期，碳、硫同位素组成延续上震旦统的负漂移现象，海侵事件、还原环境、缺氧事件、裂谷作用火山喷发、、气液喷溢、热水作用等造成海水相刘较深，有机碳埋藏量增大，多金属富集成矿。在牛蹄塘中晚期碳同位素组成趋于稳定，碳同位素组成重化，有机碳和黄铁矿含量降低：碳酸盐和有机质的碳同位素组成平均值分别是0.31±1.0‰和-31．41．3％。（沙滩），呈现稳定的正漂移；TOC平均值是0.8％；沙滩剖面郭家坝组中上部样品的黄铁矿平均含量0.5％；δ34SCRS-avg和δ34SOBS-avg为17.8士2.0‰和16.9±1.8‰。在牛蹄塘中期，随着大气圈和水圈中CO2含量降低、环境稳定，促使寒武纪生物繁盛，可能与增加的寒武系生物产量和微生物作用有关。对牛蹄塘期的环境情况有如下分析：随着全球变暖、海平面迅速上升，上升洋流活跃，由于分层海水的存在，海水在氧化带附近及其上部具有较高的有机物生成率，使寒武纪初期成为形成植物繁衍和带壳动物爆发的重要时期。碳同位素组成由震旦一寒武交变期的不稳定负漂移变化到稳定正漂移，这与世界其它地区的变化相一致。下寒武统富有机碳和黄铁矿的黑色页岩沉积，暗示了早寒武世缺氧环境的存在。（4）凯里期：早中寒武世交变期有机碳和无机碳同位素组成规律的变化，出现在扬子地台台江剖面上。有机质埋藏的变化，与生物从下寒武到中寒武统的变化相联系。碳酸盐和有机碳同位素组成的变化规律，反映了震旦一寒武交变期沉积环境的多变和震旦一寒武交变期碳循环的波动，这与变化的古环境背景、环境条件和生物演化的变化相互联系。碳酸盐碳同位素组成反映了海水最初的同位素信息；海底热液作用和上升一洋流作用可能成为影响碳同位素组成的重要因素。然而，各一地区在同一时期存在相似性，也有很大的不同，所以针对区域和局部事件，还需要进一步研究和探讨。