乍得西南部中新生代火山作用与盆地演化

Located in the Central and West African, Chad, which is not well geological explored, is characterized by Mesozoic- Cenozoic intra-continental rift basins. The boreholes exposed that, during Mesozoic-Cenozoic times, volcanic activities were intense in these basins, but study on volcanic rocks is very weak, especially on those embedded in rift basins, and so far systematic and detailed work has still no carried out. Based on the project of China National Oil and Gas Exploration and Development Corporation, “The analysis of reservoir condition and the evaluation of exploration targets of seven basins in block H in Chad”, and the cooperative project between Institute of Geology and Geophysics, CAS and CNPC International (Chad) Co. Ltd., “Chronology and geochemistry studies on Mesozoic-Cenozoic volcanic rocks from southwestern Chad Basins”, systematic geochronology, geochemistry and Sr-Nd-Pb isotopic geochemistry studies on volcanic rocks from southwestern Chad basins have been done in the thesis for the first time. Detailed geochronological study using whole-rock K-Ar and Ar-Ar methods shows the mainly eruption ages of these volcanic rocks are Late Cretaceous- Paleogene. Volcanic rocks in the well Nere-1 and Figuier-1 from Doba basin are products of the Late Cretaceous which majority of the K-Ar (Ar-Ar) ages fall in the interval 95-75 Ma, whereas volcanic rocks in the well Ronier-1 from Bongor Basin and the Well Acacia-1 from Lake Chad Basin formed in the Paleogene which the ages concentrated in 66-52Ma. Two main periods of volcanic activity can be recognized in the study area, namely, the Late Cretaceous period and the Paleogene period. Volcanic activities have a general trend of south to north migration, but this may be only a local expression, and farther future studies should be carried on. Petrology study exhibits these volcanic rocks from southwestern Chad basins are mainly tholeiitic basalt. Major- and trace elements as well as Sr-Nd-Pb isotopic geochemistry studies show that the late Cretaceous and the Paleogene basalts have a definitely genetic relationship, and magmas which the basalts in southwestern Chad basins derived from were produced by fractional crystallization of olivine and clinopyroxene and had not do suffered from crustal contamination. These basalts are prominently enriched light rare earth elements (LREE), large-ion lithophile elements (LILE) and high field strength elements (HFSE) and depleted compatible elements. They have positive Ba, Pb, Sr, Nb, Ta, Zr, Hf anomalies and negative Th, U, P,Y anomalies. It is possible that the basalts from southwestern Chad basins mainly formed by mixing of depleted mantle (DM) and enriched mantle (EMⅡ) sources. The late Cretaceous basalts have higher (87Sr/86Sr)i ratios than the Paleogene basalts’, whereas have lower (143Nd/144Nd)i ratios than the latter, showing a significant temporal evolution. The mantle sources of the Late Cretaceous basalts may have more enriched mantle(EMⅡ) compositions, whereas those of the Paleogene basalts are relatively more asthenospheric mantle (DM) components. The mantle components with temporal change observed in basalts from Chad basins were probably correlated with the asthenospheric mantle upwelling and lithospheric thinning in Central and Western Africa since Mesozoic. Mesozoic- Cenozoic Volcanism in Chad basins probably is a product of intra- plate extensional stress regime, corresponded to the tectonic setting of the whole West and Central African during Cretaceous. Volcanism is closely correlated with rifting. As time passed from early period to late, the basaltic magma of Chad basins, characterized with shallower genetic depth, higher density and smaller viscosity, probably indicates the gradual strengthening evolution of the rifting. In the initial rife stage, volcanic activities are absent in the study area. Volcanic activities are basiccally corresponded with the strong extensional period of Chad basins, and the eruption of basalts was slightly lagged behind the extensional period. In the post-rift stage (30-0Ma), these basins shifted to the thermal sag phase, volcanic activities in the study area significantly decreased and then terminated.

高温实验中重金属钼在硅酸盐熔体中的含量研究

This dissertation discusses current status of high temperature and high pressure and focuses on analyzing systematically the solubility of heavy metals in the silicate magma in HTHP experiments. The high temperature study on the content of heavy metal molybdenum in the silicate melts in this dissertation, which is granted, based on the geology mineralization model and the theory of HTHP experiments and combined with mineralization grade and geochemical nature of Mo, discusses the difference of mineralization between mantle plume and aqueous fluids and comes to the conclusions, which are as follows: (1) The content of Mo in the silicate melts is much greater than Mo mineralization grade. The molybdenum ore has the exploitation value when the industrial grade is higher than 0.06%. Mo content in different silicate melts varies because of the concentration of SiO2, that is, Mo content in the granodiorite is greater. (2) The content of Mo, which varies with reaction time, arises first and drops down in the alkali basalt melts, while variation is not too obvious in the granodiorite melts on the whole. (3) According to the picture of sample, the conclusion is not reached very well on some issues, such as the volatility and characteristic of molybdenum oxide and dependence on the geology environment.

东准噶尔和尔赛斑岩铜矿特征及其形成的构造背景

Hersai porphyry copper deposit(PCD) of eastern junggar, newly discovered copper deposit, is located at the eastern segment of the Xiemisitai-Kulankazigan-Zhifang-Qiongheba Paleozoic island arc, Eastern Junggar. The Hersai PCD is developed in a intrusive complex, characterized by intensive and multiform hydrothermal alteration, including potassic alteration, silification, chloritization，sericitization，kaolinitization and carbonatization. Granodiorite, grandiorite porphyry, granite and concealed explosion breccia are hosts of the ore bodies containing veinlet and disseminated ore. Ore-bearing granite (ZK107-1-9), granodiorite (ZK107-1-9) and Ore-barren granodiorite (HES2-1) are selected to date zircon U-Pb age by SHRIMP method, and have an age of 429.4±6.4Ma ,413.0±3.4Ma and 411.1±4.8Ma, respectively, showing that they were emplaced from Late Silurian to Early Devonian. In addition, sample ZK107-1-9 has some hydrothermal zircons with a weighted mean 206Pb/238U age of 404.9±3.7Ma which is interpreted to be related to the granodiorite porphyry. Re-Os dating of five molybdenite samples yielded a weighted average model age of 408.0±2.9Ma, indicating the metallogenic epoch of the Hersai PCD. The ore-forming age is close to the petrogenic time of garnodiorite (411-413Ma), this suggests the ore-forming porphyry is most possiblely granodiorite porphyry. Systematic major - trace elements and Rb-Sr-Sm-Nd-Pb-Hf isotopic characteristics were studied. Analysis results show that these intrusives have some interesting and special characteristics, as following:1) containing both calc-alkaline rocks and high potassium calc-alkaline rocks ; 2) have some characteristics of adakite, but not totally, such as much lower La/Yb ratios and no Eu anomaly or just faint Eu anomaly; 3) have an initial 87Sr/86Sr ratios(0.703852-0.704565) similar to that of BSE, positive εNd(t) values between 6.1 and 7.4, the initial 206Pb/204Pb values (17.576-17.912), 207Pb/204Pb values (15.400-15.453) , 208Pb/204Pb values (37.252-37.466) , and high εHf(t) values (10.2-15.4) close to the value of depleted mantle. These geochemical features suggest that these igneous rocks in the Hersai area not only have some characteristics of island arc, but also some characteristics that only appear in the continental margin arc. It is suggested that Hersai PCD is formed in the subduction setting by the partial melting of young crust. These works and advancements mentioned in the paper are helpful to understand the deposit geology, geochemistry and metallogenesis of Hersai PCD. It is also significant to understand mineralization and tectonic setting in the Qiongheba area.

东营凹陷幔源流体对原油生物标志化合物的影响研究

A large number of mantle-derived fluid activities occurred in the Dongying Sag. On the basis of the studies on the geochemical characteristics of these fluids in this sag, the spatial distribution of biomarkers in petroleum and their relationships with the parameters of mantle-derived fluids were studied, to reveal the influence of mantle-derived fluids on the biomarkers and to evaluate the reliability of these biomarkers when applied to oil-source correlation and maturity analysis. Most biomarkers used in oil correlation kept the characteristics of their sources during burial thermal evolution. Even some of them were not influenced by mantle derived fluids, such as the relative content of C27-C29 steroid（ααα20R）and C21/C23 tricyclic terpane. However, Pr/Ph and C35/C34 hopanes were sensitive to both heat energy and materiel input by the mantle-derived fluids. γ-waxnae/C30hopanes and C24 tetracyclic terpanes /C26 tricyclic terpanes responded only to thermal influence by mantle-derived fluids. They did not chemically reacted with the mantle-derived fluids. Fluorene series compounds reacted with hydrogen and / or carbon dioxide from the mantle. Mantle-derived fluids affected most maturity index. The huge thermal energy with mantle-devied fluids weakened the relationship between the maturity parameters and depth. Among them, pregnane/C27-29 steroid and Ts/(Ts+Tm) were more sensitive to the heat of the fluids. ααα20S/(20S+20R) took the second place. αββ/(ααα+αββ) and 22S/(22S+22R) were not thermally influenced by the mantle-derived fluid. Besides, the substance of mantle-derived fluids reacted with fragrants, hopanes or moretanoids and thus altered the values of MPI1, MPI2, MPR, C30 hopanes/(C30 hopanes + moretanoids) and alkyl-diben zothiophene/diben zothiophene. The thermal alernation of phenanthrene series and their spatial distribution show that the heat energy carried by mantle-derived fluids was not fierce but spread widely in Dongying Sag, which is favorable to hydrocarbon generation with little destroy. In sum, mantle-derived fluids affected biomarkers through thermal energy and chemical reactions and changed the values of oil-source correlation and maturity parameters in the deep-seated fault belts. Therefore, in the deep-seated fault belts, oil-source correlation should be restudied and the new parameters need to be explored.

内蒙古中部道郎和都格铜多金属矿的地质特征矿床类型及找矿模式研究

Daolangheduge copper polymetallic deposit is located on east edge of Ondor Sum-Bainaimiao metallogenic belt, which is a prospective area of porphyry copper deposit, in Xianghuangqi of central Inner Mongolia. Geotectonically, it occurred in the continental margin accretion belt along the north margin of North China Plate, south of the suture zone between North China Plate and Siberian Plate. The intrusive rocks in this area mainly consist of intermediate-acid magmatic rocks, and the quartz veins, tourmaline veins and the transitional phase are comparatively developed. According to our research, the ore-bearing rock body is mainly quartz diorite while the surrounding rock is mainly biotite granite. Besides, the wall rock alteration are mainly propylitization, pyritization and silicification, which consist of epidotization, actinolitization, chloritzation and so on. The metallic minerals are mainly chalcopyrite and pyrite. In addition, the primary ore is mainly of quartz-chalcopyrite-pyrite type. Above all, Daolangheduge copper polymetallic deposit is suggested to be categorized in the porphyry copper type. With isotopic dating and geochemical research on quartz diorite of ore-bearing rock body, the zircon LA-ICP-MS U-Pb dating of two samples yields an age of 266±2 Ma, falling into the range of late Permian Epoch. It is the first accurate age data in Xianghuangqi area, so it should play a key role in the research of deposit and magmatic rocks in this area. With the major elements and trace elements analysis of 14 samples, the quartz diorite should be among the calc-alkaline series, the geochemical characteristics show higher large-ion lithophile elements of Rb, Sr and LREE, low high-field strength elements of Nb, Ta and high transition elements of Cu, Cr . Also, the REE patterns have negative Eu anomalies. With the same analysis of 4 sample for the biotite granite, the geochemical characteristics show higher Rb, Th,, Zr, Hf and LREE, low Nb, Sm and HREE and Eu has no anomaly. It should be among the calc-alkaline series, over aluminum quality and has characteristics of Adakites. According to isotopic dating and geochemical characteristics of ore-bearing rock body, it is suggested that its materials mainly derived from upper mantle that had fractional crystallization and its magma source region may be affected by fluid metasomatism of paleo-asian ocean. It should be an extensional process of post-orogeny according to regional tectonic evolution. Consequently, because of the decrease of temperature and pressure, the ore forming fluid was raised to surface and mineralized accompanied by magmatic activity which might occur in south of the suture zone. By geological survey, further geophysical and geochemical work is needed. In this area, we have accomplished high precision magnetic prospecting, high density electrical survey, gravity prospecting, soil geochemical prospecting, X-ray fluorescence analyzer prospecting and so on. According to geophysical and geochemical abnormal and surface occurrence, 11 drills are arranged to verification. The type of ores are mainly quartz-chalcopyrite-pyrite ores within 3 drills by drill core logging. Although the grade as well as the scale of already-found Cu deposits are insufficient for industrial exploitation, the mineralization prospect in this region is supposed to be great and the potential in mineral exploration at depth is excellent.

碎屑锆石年龄和Nd-Hf同位素组成对扬子基底演化的制约

The South China craton was formed by the collision of the Yangtze and Cathaysia blocks during the Neoproterozoic Jiangnan orogeny (also termed as the Jingnin or Sibao orogeny in Chinese literature). Basement rocks within the Yangtze block consist mainly of Proterozoic sediments of the Lengjiaxi and Banxi Groups. U-Pb ages of detrital zircons obtained by the LA-ICP-MS dating technique imply that the deposition of the Lengjiaxi Group continued until the Neoproterozoic. The youngest detrital zircons suggest a maximum deposition age of ~830 Ma for the Lengjiaxi Group, consistent with the initiation time of the deposition of the overlying Banxi Group, likely indicating continuous deposition of these two groups and a short temporal hiatus (~10 Ma) between the Neoproterozoic sedimentary rocks distributed in the South China craton. Detrital zircons from both the Lengjiaxi and Banxi Groups have a wide range of εHf(t) values from -12 to 14.2 and a continuous Nd and Hf model age spectrum from ~820 Ma to 2200 Ma. Some grains have model ages ranging up to ca. 2.9-3.5 Ga, indicating that both juvenile mantle material and ancient crust provided sedimentary detritus. This is also consistent with the Nd isotopic signature of sedimentary rocks recorded in the Lengjiaxi Group, suggesting a back-arc tectonic setting. The Banxi Group has slightly enriched Nd isotopic signatures relative to the Lengjiaxi Group, implying a higher percentage of old continental material in the sedimentary source. Combined with previously published data, new results can help us to reconstruct the Neoproterozoic tectonic evolution of the South China craton. The age spectrum of detrital zircons and Nd-Hf isotopic composition suggests a two-stage collision: Between 1000 Ma to 870 Ma, a continental magmatic arc was build up along the eastern margin of the Yangtze block. Convergence led to continent-based back-arc extension, subsidence and formation of a back-arc basin. Detritus originating from arc-related magmatic and old basement rocks was transported into this back-arc basin resulting in formation of the Lengjiaxi Group and its equivalents. At around 870 Ma, a second (oceanic) arc was formed by extension of an inter-arc basin, subduction subsequently led to the first collision and the emplacement of the blueschist mélange. Accretion of the magmatic arc lasted until the closure of an oceanic basin between the Yangtze and Cathaysia blocks at about 830 Ma. Shortly after the collision, subsequent uplift, further extension of the former back-arc basin and post-collisional granitoid magmatism caused a tilting of the Lengjiaxi sediments. Between 830 Ma and 820 Ma, subsequent closure of the oceanic back-arc basin and formation of the Jiangnan orogen took place, leaving a regional unconformity above the Lengjiaxi Group. Above this unconformity the Banxi Group was immediately deposited during the post-tectonic stage.

人工源宽角地震资料中的广角效应及其对地壳速度成像的影响

The seismic wide-angle reflection/refraction method is the one of the most effective method for probing the crustal and upper mantle structure. It mainly uses the wide-angle reflection information from the boundary in the crust and the top boundary of the upper mantle to rebuild the crust and upper mantle structure. Through analyzing the reflection and transmission coefficients of various incident waves on the interface, we think relative to the pre-critical angle reflection information the post critical angle reflection information that received by wide-angle seismic data exists a time-shift effect with the offset variation, and then it must cause the error for velocity analysis and structure image. The feature of the wide-angle seismic wave field of the fourteen representative crust columns tell us that the wide-angle effects in the different representative tectonic units for the interface depth and the interval velocity in crust. We studied the features of the wide-angle seismic wave field through building the crust model and inverse its travel time by GA method to know the wide-angle influence on crustal velocity image. At last we finished the data processing of the Tunxi-Wenzhou wide-angle seismic profile. The results are as following: (1) Through building crust model, we labeled the travel time for all the phases by ray tracing method and remove wide-angle effects method, it revealed the wide-angle effect exists in the seismic data. (2) The travel time inversion by GA method can tell us that the depth by traditional ray tracing method is shallower than the result by remove wide-angle effects method, the latter can recover the crust structure model in effect. (3) We applied the two method mentioned before to the fourteen representative crust columns in China. It indicates that the removed wide-angle effect method in travel time inversion is reasonable and effective. (4) The real data processing from Tunxi-Wenzhou wide-angle seismic profile give us the basic structure through the two ways. The main influence exhibits in the difference of the interval velocity of the curst, and the wide-angle effects in shallow interface are stronger than the deep interface.

南海张裂大陆边缘数值模拟研究

The South China Sea (SCS) is one of the largest marginal seas in the western Pacific, which is located at the junction of Eurasian plate, Pacific plate and Indian-Australian plate. It was formed by continent breakup and sea-floor spreading in Cenozoic. The complicated interaction among the three major plates made tectonic movement complex and geological phenomena very rich in this area. The SCS is an ideal place to study the formation and evolution of rifted continental margin and sea-floor spreading since it is old enough to have experienced the major stages of the basin evolution but still young enough to have preserved its original nature. As the demand for energy grows day by day in our country, the deep water region of the northern continental margin in the SCS has become a focus of oil and gas exploration because of its huge hydrocarbon potential. Therefore, to study the rifted continental margin of the SCS not only can improve our understanding of the formation and evolution processes of rifted continental margin, but also can provide theoretical support for hydrocarbon exploration in rifted continental margin. This dissertation mainly includes five topics as follows: (1) Various classic lithosphere stretching models are reviewed, and the continuous non-uniform stretching model is modified to make it suitable for the case where the extension of lithopheric mantle exceeds that of the crust. Then simple/pure shear flexural cantilever model is applied to model the basement geometries of SO49-18 profile in the northern continental margin of the SCS. By fitting the basements obtained by using 2DMove software with modeling results, it is found that the reasonable effective elastic thickness is less than 5km in this region. According to this result, it is assumed that there is weak lower crust in the northern continental margin in the SCS. (2) We research on the methods for stretching factor estimation based on various lithosphere stretching models, and apply the method based on multiple finite rifting model to estimate the stretching factors of several wells and profiles in the northern continental margin of the SCS. (3) We improve one-dimension strain rate inversion method with conjugate gradient method, and apply it to invert the strain rate of several wells in the northern continental margin of the SCS. Two-dimension strain rate forward modeling is carried out, and the modeling results show that effective elastic thickness is a key parameter to control basin’s geometry. (4) We simulate divergent upwelling mantle flow model using finite difference method, and apply this newly developed model to examine the formation mechanism of the northwest and central sub-basin in the SCS. (5) We inverse plate thickness and basal temperature of oceanic lithosphere using sea-floor ages and bathymetries of the North Pacific and the North Atlantic based on varied-parameters plate model, in which the heat conductivity, heat capacity and coefficient of thermal expansion depend on temperature or depth. A new empirical formula is put forward based the inversed parameters, which depicts the relation among sea-floor age, bathymetry and heat flow. Then various similar empirical formulae, including the newly developed one, are applied to examine the sea-floor spread issue in the SCS based on the heat flow and bathymetry data of the abyssal sub-basin.

东天山镁铁-超镁铁岩铜镍硫化物矿床通道式成矿机制与岩体含矿性评价研究

A mafic-ultramafic complex belt well developed in Eastern Tianshan, Xinjiang, NW China, which contains a series of Cu-Ni sulfide deposits. This area is the important production basis for Cu-Ni deposits, including Tulargen deposit, Hulu deposit, Huangshan-Huangshandong deposit, Hulu deposit, Xiangshan deposit, Tianyu deposit, Chuanzhu deposit. In China, especially Eastern Tianshan, it is prevalent that large Cu-Ni deposits occurred in small intrusions, typically including Jinchuan, Kalatongke, et al., so the ore-forming mechanism and evaluation rule for those small intrusions are very meaningful and of universal significance. On the basis of the research to typical Cu-Ni deposits, ore-forming conditions and processes are summarized through which to evaluate the ore-bearing potential for barren intrusions and unexplored mafic-ultramafic intrusions. By the contrast, metallogenic rule and mechanism of ore genesis are concluded, and evaluation system is preliminarily set up on the basis of these conclusions. Quantitatively simulation for the composition of olivine is introduced for the first time in China to discuss the interaction between magma and sulfide, and a new method to calculate the Mg-Fe composition of primitive magma is developed. Interaction between magma and sulfide liquid is used to get the Ni content in sulfide liquid. Sulfur isotopic characteristics in sulfide minerals in country rocks and ores are used to judge crustal sulfur introduction, which is applied for the first time in China. Re-Os isotopic characteristics are related to the ore-forming process, to interpret the process of enrichment of chalcophile elements. On the basis of the evaluation system, Mati, Chuanzhu, Luodong, Xiadong, those intrusions are evaluated to their ore-bearing potential. According to the studies to typical Cu-Ni deposits, conduit-type ore-forming model is set up, and the characteristics of the model are concluded systematically. The evaluation system and conduit-type ore-forming model can be helpful to the evaluation of mafic-ultramafic intrusions in this and similar mafic-ultramafic intrusion belts. The studied typical deposits and mafic-ultramafic intrusion include Tulargen deposit, Hulu deposit, Huangshandong deposit, Chuanzhu deposit, Mati intrusion，Luodong intrusion, Xiadong intrusion, and others. Through studies, there are similar characteristics for Tulargen and Hulu deposits in magma origin, composition of primitive magma（MgO=12.5%, FeO=12% and MgO=11%, FeO=10.5% respectively）, magma evolution, mechanism of sulfide segregation and conduit-type ore-forming process. By Re-Os isotopic system, the ore forming date of Tulargen deposit is 265.6±9.2Ma, which is consistent to regional metallogenic event, but little younger. The Mg-Fe composition of primitive magma of Baishiquan, Huangshandong area, Kalatongke is lower than that of Tulargen and Hulu deposit, showing common basalt composition. The Mg# value（Mg#=(Mg/Mg+Fe）increases gradually from Kalatongke to Baishiquan to Huangshan-Huangshandong East. Baishiquan intrusions show relatively higher crustal contamination by evidence of trace element, which indicates the lower magma original source, from depleted mantle to crust. One break is the discovery of komatiitic intrusion, Xiadong intrusion, which shows characteristics of highly magnesium (Max Fo=96). The primitive magma is calculated of MgO=28%，FeO=9%, belonging to komatiitic magma. Tectonic evolution of Eastern Tianshan is discussed. By the statistics of ore-forming data of porphyry copper deposits, magmatic sulfide Cu-Ni deposits, orogenic hydrothermal gold deposits, we believe that those deposits are the successive products of oceanic subduction, are and back-arc basin collision and post-orogenic extention. And Cu-Ni sulfide deposits and orogenic gold deposits occurred in the stage of post-orogenic extention. According to the conclusions, the conduit-type ore-forming mechanism of magmatic sulfide deposit is set up, and its characteristics and conditions are concluded as well. The conduit-type ore-forming system includes magma generation, sulfide segregation, enrichment of chalcophile elements, interaction of sulfide and magma, sulfide collection in limited space in magma conduit and bottom of the chamber, which make a whole ore-forming system.The ore-forming process of Cu-Ni sulfide deposits is concluded as three steps: 1. mantle derived magma rises upward to the middle-upper crust; 2. magma suffers crustal contamination of different degrees and assimilates crustal sulfur, which leads to sulfur saturation and sulfide segregation. Sulfide liquid interacts with magma and concentrates chalcophile elements; 3. enriched sulfide located in the conduit(Tulargen) or bottom of the chamber (Hulu). Depleted magma rises upward continuously to form barren complexes. For the practical cases, Tulargen deposit represents the feeding conduit, and Hulu deposit represents the bottom of the staging magma chamber. So the deeper of west of Tulargen and southwest of Hulu are the favorite locate for ore location. The evaluation for ore potential can be summarized as follows: (1) Olivine can be served as indicator for magma evolution and events of sulfide segregation; (2) Sulfur isotopic characteristics is an efficient method to judge sulfur origin for magmatic sulfide deposit; (3) Re-Os content of the ores can indicate interaction between sulfide and silicate magma and crustal contamination; (4) PGE mineralization is effected by degree of partial melting of mantle; (5) Cu/Zr is efficient parameter to judge sulfide segregation; (6) The effects of multiple magma fractionation and emplacement are important, for inverse order shows the destruction to previous solid lithofacies and orebodies. Mati, Chuanzhu, Xiadong, Luodong, mafic-ultramafic intrusions are evaluated using evaluation system above. Remarkable Ni depletion is found in olivine of Mati, and southwest of the intrusion can be hopeful location for ore location. Chuanzhu intrusion has remarkable evidence of sulfide segregation, but the intrusion represents the narrow feeder conduit, so the wide part of the conduit maybe the favorite location for sulfide to deposit. The ore potential of Luodong and Xiadong is not good. Both the intrusions show no Ni depletion in olivine, and there is no sulfide in country rocks, so no crustal sulfur is added into the magmatic system. For Sidingheishan, a very large intrusion, the phenomenon of sulfide segregation is found, but there are no favorite places for sulfide to deposit. So the Cu-Ni ore potential maybe not good, but PGE mineralization should be evaluated further.

新增生岩石圈与软流圈的相互作用：来自地幔橄榄岩捕虏体的证据

The petrology and geochemistry of peridotites entrained in Beiyan Cenozoic alkaline basalts within the middle segment of Tan-Lu fault zone and clinopyroxene megacrysts in the late Mesozoic and Cenozoic alkaline basaltic rocks from the North China Craton, have been systematically investigated. The main conclusions are obtained as follows. The peridotites entrained in alkaline basalts at Beiyan, Shandong Province, China are comprised of dominantly spinel lherzolites and spinel wehrlites with porphyroclastic, granuloblastic textures to resorption textures. The xenoliths are fertile in major element compositions (High CaO, TiO2, Low MgO, Cr2O3). The olivine Fo (= 100×Mg / (Mg+Fe) possesses a low and very large range of 81.0 to 91.0. The peridotites contain high percentages (Lherzolites: 10 - 19% in volume; Wehrlites: 24 - 28% in volume) of clinopyroxene with spongy textures. The Sr and Nd isotopic ratios of clinopyroxene separates from peridotites and pyroxenite xenoliths have a depleted and small range fall within the area of MORB, similar to newly-accreted lithospheric mantle. However, the appearance of many wehrlites and highly enriched LREE pattern suggest that this newly-accreted lithospheric mantle was considerably modified and reconstructed recently through the peridotite-asthenospheric melt interaction. The upwelling of asthenosphere from late Cretaceous to Eogene and upper mantle shearing of the Tan-Lu fault played an important role in the modification and reconstruction of the newly-accreted lithospheric mantle. The clinopyroxene megacrysts in the late Mesozoic and Cenozoic alkaline basaltic rocks from the eatern North China Craton are different in aspects of major elements, trace elements and isotopic composition. The characteristics of texture, mineral compositions and geochemistry as well as the Fe-Mg partitioning between the crystal and the melt indicates that the Al-augites in the Cenozoic basalts represent high-pressure crystallization products of alkaline basaltic melts. Thus, both of clinopyroxene megacrysts and host basalts could be derived from a same primitive magma. However, the Al-augites in the late Mesozoic basaltic rocks represent accidentally-included xenocrysts of basaltic components which had crystallized in the depth from a previously melting episode. The more depleted Sr-Nd isotopic compositions of Cenozoic megacrysts compared with those of host alkaline basalts and tholeiites demonstrate that even the alkali basalts could not completely represent primitive magma initiating in asthenosphere. That is to say, the Cenozoic alkaline basalts were more or less modified by some enriched Sr-Nd isotopic components during their eruption. Meanwhile, the tholeiites were not the products formed only by fractional crystallization of alkaline basaltic magma or different degrees of partial melting. It may result from the contribution of lithospheric mantle materials or crust contamination in magma chamber to alkali basaltic magmas.

藏北可可西里碰撞后钾质火山作用和岩石成因

Post-collisional, potassic igneous rocks are widely distributed in the Hoh Xil area of the northern Tibetan Plateau. Based on the field work, petrography, mineral chemistry, K-Ar geochronology, element and Sr-Nd-Pb isotope geochemistry, this thesis systematically studied the spatial and temporal distribution of the volcanic rocks, chemical characteristics, formation mechanism and partial melting mechanism of the magma source region, geodynamic setting of magmatism, as well as crustal assimilation and fractional crystallization (AFC). The results show that: 1. The Miocene (7.77-17.82 Ma) volcanic products dominantly are trachandesite and trachy, and subordinate rhyolites, associated with stike-slip faults and thrust faults, formed morphology of small lava platforms and cinder cones. 2. Phenocrysts in the lavas are augite, andesine, sanidine, calcic amphibole and subordinate orthopyroxene, biotite and Ti-Fe oxides, displaying typical quench texture. Equilibrium temperatures and pressures of clinopyroxene phenocrysts indicate the magma chamber is located in upper-middle crust. 3. Rhyolites are the products of crustal melting and fractionation of shoshonitic magmas. The source region of intermediate magmas is enriched continental lithospheric mantle, which contains residual minerals such as phlogopite, rutile and spinel, and enriched by subducted sediments during earlier multi-episodes of subduction. 4. Upwelling of asthenosphere provides heat for source region melting, and faults provide channels for magma eruption. 5. Northward underthrusting of Indian continental lithosphere and southward of backstop of Asian continental lithosphere resulted in upwelling of hot asthenosphere. Geochemical characteristics of the potassic magmatism in North Tibet are dominantly controlled by source region composition, partial melting, and crustal assimilation and fractional crystallization (AFC).

东喜马拉雅构造结新生代碰撞变形与岩石圈演化

The Eastern Himalayan Syntaxis (EHS) is one of the strongest deformation area along the Himalayan belt resulted from the collision between Indian plate and the Eurasian Plate since the 50～60Ma, and has sensitivity tracked and preserved the whole collisional processes. It should depend on the detail geological investigations to establish the deformational accommodate mode, and the uplift history, to elucidate the deep structure and the crust-mantle interaction of the Tibet Plateau of the EHS. The deep-seated (Main Mantle Thrusts) structures were exhumed in the EHS. The MMT juxtapose the Gangdese metamorphic basement and some relic of Gangdese mantle on the high Himalayan crystalline series. The Namjagbawa group which is 1200～1500Ma dated by U/Pb age of zircon and the Namla group which is 550Ma dated by U/Pb age of zircon is belong to High Himalayan crystalline series and Gangdese basement respectively. There is some ophiolitic relic along the MMT, such as metamorphic ocean mantle peridotite and metamorphic tholeiite of the upper part of ocean-crust. The metamorphic ocean mantle peridotites (spinel-orthopyroxene peridotite) show U type REE patterns. The ~(87)Sr/~(86)Sr ratios were, 0.709314～0.720788, and the ~(143)Nd/~(144)Nd ratios were 0.512073～0.512395, plotting in the forth quadrant on the ~(87)Sr/~(86)Sr-~(143)Nd/~(144)Nd isotope diagram. Some metamorphic basalt (garnet amphibolite) enclosures have been found in the HP garnet-kynite granulite. The garnet amphibolites can be divided two groups, the first group is deplete of LREE, and the second group is flat or rich LREE, and their ~(87)Sr/~(86)Sr, ~(143)Nd/~(144)Nd ratios were 0.70563～0.705381 and 0.512468～0.51263 respectively. Trace element and isotopic characteristics of the garnet amphibolites display that they formed in the E-MORB environment. Some phlogolite amphibole harzburgites, which exhibit extensive replacement by Phl, Amp, Tc and Dol etc, were exhumed along the MMT. The Phl-Amp harzburgites are rich in LREE and LILE, such as Rb, K etc, and depletes Eu (Eu~* = 0.36 ～ 0.68) and HFSE, such as Nb, Ta, Zr, Hf, P, Ti etc. The trace element indicate that the Phl-Amp harzburgites have island arc signature. Their ~(87)Sr/~(86)Sr are varied from 0.708912 to 0.879839, ~(143)Nd/~(144)Nd from 0.511993 to 0.512164, ε Nd from- 9.2 to - 12.6. Rb/Sr isochrone age of the phlogolite amphibole harzburgite shows the metasomatism took place at 41Ma, and the Amp ~(40)Ar/~(39)Ar cooling age indcate the Phl-Amp harzburgite raising at 16Ma. There is an intense crust shortening resulted from the thrust faults and folds in the Cayu block which is shortened more 120km than that of the Lasha block in 35～90Ma. With the NE corner of the India plate squash into the Gangdese arc, the sinistral Pai shear fault and the dextral Aniqiao shear fault on the both sides of the Great bent of Yalun Zangbu river come into active in 21～26Ma. On the other hand, the right-lateral Gongrigabu strike-slip faults come into activity at the same period, a lower age bound for the Gongrigabu strike-slip fault is estimated to be 23～24Ma from zircon of ion-probe U/Pb thermochronology. The Gongrigabu strike-slip faults connect with the Lhari strike-slip fault in the northwestern direction and with the Saganing strike-slip at the southeastern direction. Another important structure in the EHS is the Gangdese detachment fault system (GDS) which occurs between the sedimental cover and the metamorphic basement. The lower age of the GDS is to be 16Ma from the preliminary 40Ar/39Ar thermochronology of white mica. The GDS is thought to be related to the reverse of the subducted Indian crust and the fast uplift of the EHS. Structural and thermochronology investigation of the EHS suggest that the eastern Tibet and the western Yunnan rotated clockwise around the EHS in the period of 35～60Ma. Later, the large-scale strike-slip faults (RRD, Gaoligong and Saganing fault) prolongate into the EHS, and connect with the Guyu fault and Gongrigabu fault, which suggest that the Indianchia block escape along these faults. Two kind of magmatic rocks in the EHS have been investigated, one is the mantle-derived amphibole gabbro, dioposide diorite and amphibole diorite, another is crust origin biotit-garnet adamellite, biotit-garnet granodiorite and garnet-amphibole-biotite granite. The amphibole gabbro dioposite diorite and amphibole diorite are rich in LREE, and LILE, such as Ba, Rb, Th, K, Sr etc, depleted in HFSE, such as Nb, Ta, Zr, Hf, Ti etc. The ratio of ~(87)Sr/~(86)Sr are from 0.7044 to 0.7048, ~(143)Nd/~(144)Nd are from 0.5126 to 0.5127. The age of the mantle origin magamatic rocks, which result from the partial melt of the raising and decompression anthenosphere, is 8Ma by ~(40)Ar/~(39)Ar dating of amphibole from the diorite. The later crust origin biotite-garnet adamellite, biotite-garnet granodiorite and garnet-amphibole-biotite granite are characterized by aboudance in LREE, and strong depletion of Eu. The ratios of ~(87)Sr-~(86)Sr are from 0.795035 to 0.812028, ~(143)Nd/~(144)Nd from 0.51187 to 0.511901. The ~(40)Ar/~(39)Ar plateau age of the amphibole from the garnet-amphibole-biotite granite is 17.5±0.3Ma, and the isochrone age is 16.8±0.6Ma. Their geochemical characteristics show that the crust-derived magmatic rocks formed from partial melting of the lower curst in the post-collisional environment. A group of high-pressure kaynite-garnet granulites and enclave of high-pressure garnet-clinopyroxene grnulites and calc-silicate grnulites are outcroped along the MMT. The peak metamorphic condition of the high-pressure granulites yields T=800～960 ℃, P=1.4～1.8Gpa, corresponding the condition of 60km depth. The retrograde assemblages of the high-pressure grnulites occur at the condition of T=772.3～803.3 ℃, P=0.63～0.64Gpa. The age of the peak metamorphic assemblages are 45 ～ 69Ma indicated by the zircon U/Pb ion-plobe thermochronology, and the retrograde assemblage ages are 13～26Ma by U/Pb, ~(40)Ar/~(39)Ar thermochronology. The ITD paths of the high-pressure granulites show that they were generated during the tectonic thickening and more rapid tectonic exhumation caused by the subducting of the Indian plate and subsequent break-off of the subducted slab. A great deal of apatite, zircon and sphene fission-track ages, isotopic thermochronology of the rocks in the EHS show that its rapid raising processes of the EHS can be divided into three main periods. There are 35～60Ma, 13～25Ma, 0～3Ma. 3Ma is a turn in the course of raising in the EHS which is characterized by abruptly acceleration of uplifting. The uplift ratios are lower than 1mm .a~(-1) before 3Ma, and higher than 1mm .a~(-1) with a maximum ratio of 30mm .a~(-1) since 3Ma. The bottom (knick point) of the partial anneal belt is 3.8km above sea level in the EHS, and correspond to age of 3Ma determined by fission-track age of apatite. The average uplift ratio is about 1.4 mm .a~(-1) below the knick point. The EHS has raised 4.3km from the surface of 2.36km above sea level since 3Ma estimated by the fossil partial anneal belt of the EHS. We propose a two-stage subduction model (B+A model) basing on Structural, thermochronological, magmatical, metamorphic and geophysical investigations of the EHS. The first stage is the subduction of the Indian continental margin following after the subduction of the Tethys Ocean crust and subsequent collision with the Gangdese arc, and the second stage is the Indian crust injecting into the lower crust and upper mantle of the Tibet plateau. Slab break-off seems to be occurred between these two stages.

五台山区义兴寨岩体、车厂－北台岩体地球化学和变质作用及其大地构造意义

There are many Archean TTG grey suites in the Wutaishan area, northern Shanxi Province, China. In the past one hundred years, many geologists have done excellent research work in the Wutaishan and its adjacent regions. However, the TTG suites were almost neglected. Located in the northern slope of Mt. Hengshan-namely the Archean Hengshan Island Arc, intruded the Zhujiafang supercrustal rocks at almost 2.5Ga, the Yixingzhai TTG Suite is originated from partial melting of the ancient lower crust upper mantle by REE and trace elements, and the emplacement occurred in an Archean island arc. The rocks are mainly of tonalitic, I type, and calc-alkaline trends are found in the magmatic evolution. At almost 1.8 Ga, the suite was transformed to be dome-like schists in an arc-arc collision event, and the rocks were metamorphosed to an extent of amphibolitic to granulitic facies. The peak metamorphic condition is of 710-760 ℃/0.68-0.72GPa, and the subsequent cooling history is recorded as 560-620 ℃/0.46-0.60GPa. In the center of the Mt. Wutaishan-known as the Archean Wutaishan Island Arc, intruded the Archean Chechang-Beitai TTG Suite, which is of 2.5Ga old and of trondhjemitic and tonalitic, with coexisting I- and S-types and a trondhjemitic magmatic evolution trend. Through REE and trace elements, the suite is believed to be from the partial melting of the ancient lower crust or upper mantle. The 1.8 Ga collision event also made the suite gneissic and the it was metamorphosed to be amphibolitic facies, whose peak condition is approximately of 680 (±50) ℃/0.7Gpa, and the subsequent cooling process is recorded as 680 (±50) ℃、550(±50) ℃、420(±10) ℃. Crustal growth is fulfilled through magmatic intrusion as well as eruption at about 2.5Ga, arc-arc collision at about 1.8 Ga in the Wutaishan area and its environs. Additionally, the biotite-muscovite and muscovite-plagioclase geothermometers are refined, and the biotite-hornblende geothermometer is developed in this dissertation.

南海北部大陆边缘盆地深部地热特征用地球动力学演化

This report is a conclusion of the major research outcome during my post-doctoral residence of research and work. Its content covers the researches of the deep thermal characteristic and dynamics evolution beneath the northern margin basin of South China Sea. In this report, the each other action and effect between lithosphere ad mantle convection were regarded by the combine of deep and shallow study, subdivision from whole to part, and pay equal attention to determine the nature and fixed quantity. The investigative method we used in this report is geothermal and gravity methods. By the help of geological model and geophysics modeling, we calculated lithosphere thermal structure, rheology structure and mantle convection. Firstly, the report introduces concisely the purpose and the previous achievement to this research. Then, it analyzed the characteristic of heat flow on South China Sea. The structure of deep temperature and thermal has been calculated in some models of heat generation and conduction. The rock rheology structure also was computed by the relationship between temperature and viscosity. All these calculations were finished under the guidelines of combine with geology and geophysics. Meanwhile, the fields both deep mantle convection and small scale upper mantle convection are computed. Beside, the density and temperature disorder resulted by mantle convection were also computed with the convection field. After these, the report bring the contribution of local field of mantle convection, thermal construct and effective viscosity beneath the northern margin basin of South China Sea. And, base on the tectonic background and evolution feature, this report discussion the evolution mechanism of south China Sea and its northern margin basin. The end of this report, the main conclusion of this research was summarized and brings out.

藏东及滇东南新生代钾质岩浆作用及其深部制约

The dissertation focuses on the petrology, geochemistry of the volcanic rocks in east Tibet and southeast Yunnan. It lucubrates the Magmatic process, forming mechanism and the possible tectonic settings of the volcanic rocks. The volcanic rocks of Nangqen basin in east Tibet, Qinghai province are mainly Cenozoic intermediate-acid shoshonites. The rocks are LREE enriched and the LREE/HREE = 3～34; (La/Yb)_N = 18.17-53.59, and ΣREE 222～1260μg/g. There are no Eu anomaly, and Nb, Ta, Zr, Hf, Ti are markedly depleted. The isotopic composition is ~(87)Sr/~(86)Sr = 0.70497～0.70614, ~(206)Pb/~(204)Pb = 18.622～18.974, ~(208)Pb/~(204)Pb = 38.431～38.996, ~(207)Pb/~(204)Pb = 15.511～15.613, respectively. K-Ar age of the whole rocks and the single mineral are between 32.0-36.5Ma. Based on the trace elements and isotopic elements, we get the conclusion that the partial melting is one of the dominated forming mechanisms for the volcanic rocks in Naneqen basin. The magma did not experience the crustal contamination en route to the surface; however, the complex mixture took place in the upper mantle before the melt was formed. There are at least two kinds of mixed sources that can be identified. The basalt in southeast Yunnan province is studied. They are distributed in Maguan, Tongguan, and Pingbian County, which is located on the both sides of the Red River belt, and the ultrabasic xenolith are cursory introduced. The volcanic rocks belongs to the alkali series, which can be subdivided into trachybasalt and basanite(Ol normal molecule >5). The volcanic rocks are characteristics by high Ti and low Mg#. According to the magma calculation model, the original rocks of the basalt in southeast Yunnan province are Spinel Lherzolite in Tongguan, Garnet Lherzolite in Pingbian and Maguan, while Togguan undergoes 2-5 percent and percent of partial melting, whereas volcanism in Maguan and Pingbian was so complex to calculate. The fractional crystallization took place during the magma evoltion in southeast Yunnan. The basalt is enriched in LREE with LREE/HREE=9.23-20.19. All of the trace elements display weak Nb, Ta peak, and the depletion of Zr, Hf and Ti in Maguan and pingbian represent the presence of Garnet in the source. The composition of the isotope ratio are ~(87)Sr/~(86)Sr = 0.70333-0.70427, ~(143)Nd/~(144)Nd = 0.512769-0.512940, ~(206)Pb/~(204)Pb = 18.104-18.424, ~(207)Pb/~(204)Pb = 15.483 -15.527; ~(208)Pb/~(204)Pb = 37.938-38.560, respectively, which shows the characteristics of the HIMU type OIB. The volcanic rocks of the southwest Yunnan are derived from the enriched, OIB type mantle sources by synthesizing all the data from trace and isotope elements. It is similar to that of the volcanic rocks in Hawaii, a typical kind of the mixtures of the recycled oceanic crust plume and depleted asthenosphere. To sum up, the volcanic rocks in southeast Yunnan are formed by the intraplate hotpot volcanism.