松辽盆地长岭断陷火山岩气藏的形成条件与分布规律

Changling fault depression is a compound fault depression complicated by interior fault, with faults in the west and overlap in the west. North of Changling fault depression show NNE strike while south is NW strike. Changling fault depression has undergone twochasmic stage which control the development and distribution of volcanic rock, one depression stage, later inversion and uplift stage which control the formation of natural gas reservoir, and basin atrophic stage. The main boundary faults and main faults in Changling fault depression control three volcanic cycles and the distribution of volcanic rock. Seismic reflection characteristic and logging response characteristic of volcanic rock in study area are obvious, and the distribution characteristic, volcanic cycle and active stage of volcanic rock can be revealed by seismic attribute, conventional logging data can distinguish clastic rock from volcanic rock or distinguish partial different types of volcanic rock. The reservoir property of rhyolite and volcanic tuff are the best. Favorable volcanic reservoir can be preserved in deep zone. Imaging logging and frequency decompostion technology of seismic data act as effective role in the study of reservoir physical property and gas-bearing properties of volcanic rock.. Hydrocarbon gas in study area is high and over mature coal type gas, the origin of CO2 is complex, it is either inorganic origin or organic origin, or mixing origin. Hydrocarbon gas is mainly originate from Shahezi formation and Yingcheng formation source rocks, CO2 is mainly mantle source gas. Hydrocarbon has the characteristics of continuous accumulation with two charging peak. The first peak represent liquid hydrocarbon accumulation time, The second peak stand for the accumulation time of gaseous hydrocarbon.CO2 accumulate approximately in Neocene. The source rock distribution range, volcanic rock and favorable reservoir facies, distribution characteristic of deep fault (gas source fault) and late inversion structure are the major factors to control gas reservoir formation and distribution. All the results show that these traps that consist of big inherited paleo uplift(paleo slope), stratigraphic overlap and thinning out, volcanic rock, are the most advantageous target zone.

西天山造山带古生代构造演化与地壳增生—来自花岗岩和蛇绿岩的证据

The Central Asian Orogen Belt (CAOB), which is different from the subductional orogen and the collisional orogen, is known as the most important site of crustal growth in the Phanerozoic, and it has been a ‘hot spot’ for studying the orogenic belts. The Chinese West Tianshan Orogen is occupying the west-southern part of the CAOB and is of great importances to understand the orogenic processes and the continental growth in the Central Asia. The West Tianshan Orogen had undergone complex tectonic evolutional processes in Paleozoic times and large volumes granitic rocks have recorded important information about these processes. Litter is known about Phanerozoic continental growth in the Western Tianshan area so far, compared with the other areas of the CAOB, such as eastern Junggar, western Junggar, Altai and Alakol. The aim of this dissertation is to set up the chronology frame of granitoids in western Tianshan, provide new evidence for the tectonic evolution and discuss the Paleozoic continental growth in this area, on the basis of the studies on the isotopic chronology, major element, trace element and Nd-Sr isotopic geochemistry of granitoids and the isotopic chronology and geochemistry of the ophiolites in this area, especially the Kule Lake ophiolites. 25 precise SHRIMP U-Pb zircon and LA-ICPMS U-Pb zircon ages have been obtained in this dissertation. The granitic rocks in western Tianshan had been formed during two periods: the granitic gneiss with an age of 896Ma, possibly representing the forming age of the Precambrian basement; the granitic rocks with ages varying from 479Ma to 247Ma, recording the Paleozoic orogenic process of western Tianshan. The granitoids in western Tianshan are composed of intermediate-basic rocks, intermediate rocks, intermediate-acid rocks and acid rocks, mainly intermediate-acid rocks and acid rocks. They are mostly granite, granodiorite, quartz syenite and monzodiorite. Different types of granitic rocks are exposed in different tectonic units. The granitoids on the northern margin of the Yili Plate mainly formed in late Paleozoic (413Ma ~ 281Ma), those with ages varying from 413Ma to 297Ma show continental arc affinities and the magnesian calc-alkalic metaluminous diorite of 281Ma display the geochemical characteristics similar to those of granites formed during the post-orogenic period. The granitiods on the southern margin of the Yili Plate include the adakite diorite of 470Ma which was formd by partial melting of thickened lower crust, the post-collisional alkali-feldspar granite of 430Ma, the volcanic arc granite of 348Ma and the Triassic post-collisional granite. The granitoids in the Central Tianshan Plate formed in 479Ma ~ 247Ma, mainly in 433Ma ~ 321Ma. The granitic rocks with ages of 479Ma ~ 321Ma are magnesian calc-alkalic to alkalic rocks with continental arc affinities. A few post-collisional granitoids of 276Ma ~ 247Ma may have inherited the geochemical characteristics of pre-existing arc magma. The granitic rocks in Southern Tianshan (northern margin of the Tarim plate) formed two stages, 420Ma ~ 411Ma and ca. 285Ma. The magnesian calcic to alkalic granites of 420Ma ~ 411Ma may formed during the extension process of the continental margin. The granite of 285Ma includes mostly ferroan calc-alkalic to alkali-calcic rocks with high SiO2 and high alkaline contents, and obviously negative anomaly of Eu, Ba, Sr, P, Ti, similar to the geochemical characteristics of the A-type granite which is formed during post-collisional extension. The Kule Lake ophiolite in southern Tianshan shows the affinity of N-MORB. A SHRIMP zircon U-Pb age of 425±8Ma has obtained for gabbros. Some zircons have given another group of 206Pb/238U age 918Ma, which may indicate the information of the pre-exist old basement rock. The small oceanic basin represented by Kule Lake ophiolite probably developed on the split northern margin of Tarim block. A model for Paleozoic tectonic evolution of the West Tianshan Orogen has been proposed here on the basis of the new results obtained in this dissertation and the previous published data. In Early Cambrian, the Terskey Ocean occurred along the North Nalati fault (NNF), and it separated the Yili plate from the Central Tianshan plate which was probably connected with the Tarim plate. The Terskey Ocean probably subducted towards south under the Central Tianshan plate and towards north under the Yili plate simultaneously. In the early stage of Late Ordovician, the Terskey Ocean had been closed, and the Yili and Central Tianshan plates collided. Meanwhile, extension happened within the joint Central Tianshan and Tarim plates gradually and the Paleo-South Tianshan Ocean had been formed. In Early Silurian, the Paleo-South Tianshan Ocean began to subduct beneath the composite Yili-Central Tianshan plate, which was intruded by volcanic arc granitoids. In Middle Silurian, the Paleo-South Tianshan Ocean, which had reached a certain width, was subducting strongly. And this subduction may have produced voluminous granitoids in the Central Tianshan plate. In the latest stage of Carboniferous, the Paleo-South Tianshan ocean closed, and the Yili-Central Tianshan plate and Tarim plate collided. In Late Cambrian, Paleo-Junggar Ocean occurred to north of the Yili plate; and started to subduct towards south under the Yili plate in Ordovician. This subduction may have produced a magma arc on the northern margin of the Yili plate. In Late Carboniferous, the Paleo-Junggar Ocean had been closed. The Yili-Central and Junggar plates amalgamated together. The West Tianhan Orogen may undergo a post-collisional collapse since Permian. And the magmatic activities may continue to early Triassic. The initial 87Sr/86Sr ration of the granitic rocks in the western Tianshan Mountains varies from 0.703226 to 0.716343, and Nd（t）from -6.50 to 2.03. The characteristics of Sr-Nd isotope indicate that the source of granitic material is not a sole source, which may be produced by mantle-crust magma mixing. In Paleozoic time, lateral growth of the continental crust along active continental margins was dominant, whereas the vertical growth of continental crust resulted from post- collisional mantle derived magmas was not obvious.

辽河盆地西部凹陷深部流体的地球化学特征与成藏效应

The main research area of this thesis is the Western Depression in the Liaohe Basin. Based on the drilling core observation and mud logging data, the features of the mantle–derived fluids and their effects on oil/gas generation in the Western Depression of the Liaohe Basin,was studied with comprehensive methods of volcanic petrology, sediment petrology, fluid geochemistry, sedimentlogy, and structural geology, and use of polarized light microscope, fluorescence microscope, electron microscope, fluid and melt inclusion test, and isotopic test of nature gas etc. The observation of drill cores in study area and other studies reveal that the main passageway of the volcanic eruption in the Cenozoic was the Xibaqian-Gaosheng fault, and the volcanic rocks of each stage were distributed around it. Mantle-derived fluid which affected on oil/gas generation formed later than the volcanic spew and those fluids entered into the depression through the Taian-Dawa fault and the Central fault. The volatile fraction analysis of the melt inclusion reveals the presence of two kinds of mantle fluids; they are hydrogen-rich fluid and carbon dioxide-rich fluid. These the two kinds of fluids were mainly distributed in olivine and pyroxene respectively. The hydrothermal veins development have multiple stages, from high temperature quartz vein to low temperature calcite vein and analcime vein, in which the fluid inclusion extremity component are methane and carbon dioxide, which indicate that when mantle-derived fluids ascended and entered into the basin, most of these fluids interacted with the organic matter in the basin even though some of these entered into atmosphere. The present isotopic test of the nature gas reveals the high 3He/4He value between the region of the Taian-Dawa fault and the Central fault, which also imply the feature of origin in mantle. This phenomenon indicates that the Mesozoic basement faults and the main Cenozoic faults had connected crust and the mantle during the basin evolution, so the mantle derived fluids could enter the basin along those faults. The main source rocks of the ES3 and ES4 members of the Shahejie Formation began to expel hydrocarbon at the end period of the ES1 member of the Shahejie Formation, and reached its peak during the period of the Dongying Formation deposition. During these periods, the mantle derived-fluids entered the basin constantly along the main faults, and supplied lots of hydrogen for hydrocarbon generation. Though the volcanic rocks and the mantle-derived fluids in the Eastern Depression were more developed than in the Western Depression, the source rocks and the deep fluids were not interacted better than the Western Depression because of the affection of structural evolution. In the Eocene, the Eastern Depression did not deposit the ES4 member of the Shahejie Formation, furthermore, the mantle-fluid formed in the Fangshengpao stage escaped to the atmosphere, which confined the later stage hydrocarbon generation capability.

均衡重力异常计算与综合解释——以黄海地区为例

Petroleum and Natural Gas is an important strategic resources. The reserves of Petroleum and Natural Gas can’t meet the need of our country, which also blocks the development of economy and threatens the safety of national. Therefore, it makes a great sense to bring “the second round of oil & gas exploration” into effect and study the exploration of oil and gas of Pre-Cenozoic residual basins in China. The integrated geophysical exploration is the main way to research the Pre-Cenozoic residual basins. Gravity exploration is one of the most important exploration methods, which has played an important role in oil and gas prospecting, such as compartmentalizing geotectonic elements, delineating the distribution range of sedimentary basins, searching oil and gas structure, abstracting oil and gas information, and so on, from its naissance. The isostatic gravity anomalies is significant for exploration, which can help us research deep crustal structure, the equilibrium state of earth, the geologic structure of shallow crust, the basement shape of sedimentary basins and the genetic evolution of sedimentary basins. In the paper, we stress the implication and physical meanings systemically, and discuss the calculation theory. On the basis of previous work, we test different isostatic compensation models and parameters to find out their influences to the result of isostatic gravity anomalies. In addition, we improve the method of isostatic gravity anomalies calculation and give a system of isostatic gravity anomalies calculation which is proved has satisfying effect. From the research above, we find that the results of Platt model and Airy model are consistent, which have similar form and almost the same value. However, by contrast, the Airy model is proved has better adaptability than Platt model. The two main parameters——crust thickness and density difference of crust and mantle, both have influence to the isostatic gravity anomalies, but the latter have more. Finally, we adopt the regional field extending edge method to make the result more of actual geologic condition. On the methods above, we calculate the isostatic gravity anomalies field in Yellow Sea area from the Bouguer gravity anomalies and the water depth and altitude data. And then the isostatic gravity anomalies character is analyzed and the integrated geological-geophysical interpretation is made on the basis of summarizing the previous research result systemically and analyzing other geophysical data and geological information. From the research, we find that the Yellow Sea area belongs to continental type crust equilibrium regions, where the isostatic gravity anomalies field is placid and has less fluctuation values, which implies that the area is in equilibrium state to different extends.

地幔压力下CaSiO3 Perovskite状态方程和弹性常数的第一性原理研究

In the past decade density functional theory (DFT) has made its way from a peripheral position in quantum chemistry to center. Of course the often excellent accuracy of the DFT based methods has provided the primary driving force of this development. This dissertation is devoted to the study of physical and chemical properties of planetary materials by first-principle calculation. The concerned properties include the geometry, elastic constants and anisotropy. In the first chapter, we give a systematic introduction to theoretical background and review its progress. Development of quantum chemistry promotes the establishment of DFT. Theorem of Hohenberg-Kohn is the fundament of DFT and is developed to Kohn-Sham equation, which can be used to perform real calculations. Now, new corrections and extensions, together with developed exchange-correlation, have made DFT more accurate and suitable for larger systems. In the second chapter, we focus on the calculational methods and technical aspects of DFT. Although it is important to develop methods and program, external package are still often used. At the end of this chapter, we briefly some widely used simulation package and the application of DFT. In the third chapter, we begin to focus on properties of real materials by first principles calculation. We study a kind of minerals named Ca perovskite, investigate its possible structure and anisotropy at Earth’s mental condition. By understanding and predicting geo-physically important materials properties at extreme conditions, we can get the most accurate information to interpret seismic data in the context of likely geophysical processes.

地震层析成像与天山地区的壳幔深部结构研究

The Tien Shan is the most prominent intracontinental mountain belt on the earth. The active crustal deformation and earthquake activities provide an excellent place to study the continental geodynamics of intracontinental mountain belt. The studies of deep structures in crust and upper mantle are significantly meaningful for understanding the geological evolution and geodynamics of global intracontinental mountain belts. This dissertation focuses on the deep structures and geodynamics in the crust and upper mantle in the Tien Shan mountain belt. With the arrival time data from permanent and temporal seismic stations located in the western and central Tien Shan, using seismic travel time tomographic method, we inversed the P-wave velocity and Vp/Vs structures in the crust and uppermost mantle, the Pn and Sn velocities and Pn anisotropic structures in the uppermost mantle, and the P-wave velocity structures in the crust and mantle deep to 690km depth beneath the Tien Shan. The tomographic results suggest that the deep structures and geodynamics have significant impacts not only on the deformations and earthquake activities in the crust, but also on the mountain building, collision, and dynamics of the whole Tien Shan mountain belt. With the strongly collision and deformations in the crust, the 3-D P-wave velocity and Vp/Vs ratio structures are highly complex. The Pn and Sn velocities in the uppermost mantle beneath the Tien Shan, specially beneath the central Tien Shan, are significantly lower than the seismic wavespeed beneath geological stable regions. We infer that the hot upper mantle from the small-scale convection could elevate the temperature in the lower crust and uppermost mantle, and partially melt the materials in the lower crust. The observations of low P-wave and S-wave velocities, high Vp/Vs ratios near the Moho and the absences of earthquake activities in the lower crust are consistent with this inference. Based on teleseismic tomography images of the upper mantle beneath the Tien Shan, we infer that the lithosphere beneath the Tarim basin has subducted under the Tien Shan to depths as great as 500 km. The lithosphere beneath the Kazakh shield may have subducted to similar depths in the opposite direction, but the limited resolution of this data set makes this inference less certain. These images support the plate boundary model of converge for the Tien Shan, as the lithospheres to the north and south of the range both appear to behave as plates.

中祁连花岗岩年代学、地球化学及其构造意义

The Qilian Orogenic Belts had undergone very complicated evolutional histories and play an important role in understanding the tectonic evolutions of old terrains in northwestern China, in which granitiods formed during Proterozoic-early Mesozoic are widely outcropped. Detailed studies of these granitiods can shed some light on the tectonic evolution of this region. In this thesis, we have conducted geochronological and geochemical studies on eight selected granitic plutons to unravel their emplacement ages and petrogenesis. Furthermore, their tectonic implications were also discussed based on these results. In Neo-Proterozoic, our results suggest that two stages of magmatic activities were taken place in Central Qilian Block, GroupⅠ(750-790Ma) and Group Ⅱ(845－ 930Ma). In Neo-Paleozoic, most granitic plutons were emplaced from Ordovician to Devonian, whereas granitiods with Triassic ages have also been discovered in South Qilian Belt. Inherited zircons with old ages of 1.7Ga, 2.1Ga and 2.7Ga have also been obtained in our study. Geochemical studies suggest that the Proterzoic granites were produced under high pressures and low temperatures from metamorphosed protolith rocks with compostions from basic to intermediate. This implies that some hot sources were underplated beneath lithosophere via mantle-derived magmatism. In combination with regional geological data, we propose that the Cental Qilian block was an old arc terrene during Precambrian, and two stage granitoids were formed under a back-arc extensional setting. Granitic rocks emplaced in early Paleozoic belong to strong peraluminous S-type granites, which were derived from metagreywacke having strong relationships with collisional process. Together with previous data, our results indicate that granitoids in Qilian Orogenic Belt formed during early Paleozoic have different petrogenesis and emplaced ages, which reflect that Qilian Orogenic Belt had underwent complicated multi-stage subduction-collusional processes in early Paleozoic. On the other hand, granitic rocks in South Qilian Belt with Triassic ages were formed by subduction of East Kulun during early Paleozoic-Late Mesozoic, which represent another orogenic episode in the northern margin of Tibetan Plateau.

内蒙古白云鄂博地区元古宙构造-岩浆演化史与超大型REE-Nb-Fe矿床成因

Bayan Obo giant REE-Nb-Fe deposit in the northen margin of the North China Craton (NCC) is well known in the world for its abundant rare earth element resources. There is nearly one hundred year of studying history in substance component, chronology and geochemistry of the ore deposit, since the main ore body was found in 1927. However, there still exist remarkable divergences in genesis, mineralized age and material origin. Especially the REE enrichment mechanism leaves us a secret. Recent research shows that the Bayan Obo ore deposit likely resulted from the carbonatite magma activity, which is a favorable factor for REE accumulation. Based on the analysis of tectonic evolution history of north margin of NCC this thesis mainly discussed the formation background of cratonic margined rifts in Bayan Obo, and presented the analytical results of formation environment, intrusion age and deep origin of Proterozoic carbonatite magma. These research results can provide evidence for ore genesis. LA ICP-MS U-Pb dating on zircon shows that the Neoarchean basement was mainly composed of calc-alkaline TTG gneisses (2588±16Ma). The collision orogeny movement of the northen margin of the NCC between 2.0 Ga to 1.9 Ga brought the swarm of diorite-granodiotite magma (2023±16Ma) and intense regional metamorphism event (1906.3±7.7 Ma to 1892.7±6.7 Ma). In the sequent super continent break up background, intense metamorphic and deformed basement complex was uplifted to the surface suffered denudation, forming Mesoproterozoic Bayan Obo group in the contemporary continental margin rifts. The uplift of basement complex and formation of continental rifts were likely related with mantle plume activity. Evidence from petrological and geochemical data suggests that abundant alkaline-basic magma resulted from enhancement of continental breakup activity, that separated into carbonatite veins and mafic dykes by melt immiscibility mechanism, intruded in Bayan Obo margin rifts at the late stage of extension movement. Carbonatite veins can be divided into three main types by mineral composition: dolomite carbonatite, dolomite-calcite coexistent carbonatite and calcite carbonatite. Intrusion relationship between different types of carbonatite veins show that the calcite carbonatite veins were formed latter than the dolomite type as well as the coexistent type. Moreover, geochemical data also reveals successive and evolutive character between them. The content of REE increases together with the calcite minerals component. That is to say that REE gradually accumulated as the evolution of carbonatite magma. High precision Sm-Nd isochron data shows that the intrusion age of carbonatite veins was at 1319±48Ma. Moreover, the REE mineralization age in calcite carbonatite veins was around 1275±87Ma that is consistent with the intrusion age in error range. According to these data the abundant REE already existed in the carbonatite magma before intrusion and result in the earlier ore mineralization. The average age of mineralized dolomite was at 1353±100Ma, and the mineralization age of apatite in coarse grain dolomite was around 1329±150Ma. These data is consistent with carbonatite. Considering the coincident rare, trace element and isochron composition between them, it is presumed that mineralized dolomite was also the carbonatite intrusion and was the mainly factor for huge REE enrichment.

青藏高原东部长周期大地电磁测深研究

As a complement to conventional MT, Long-period Magnetotellurics (LMT) has been developed at low frequency for soundings of deep electric structures. Eastern Himalayan Syntaxis (EHS) and surrounding area is a key place for the study of dynamics of the uplift of Tibetan plateau. Experiments in the pioneer studies for EHS3D project showed that the study area shares an unusual low resistive crust and upper mantle. Conventional MT could not provide sufficient information about the deep structures of the study area that requested long period MT measurement to be complemented. This thesis presents the LMT studies in eastern Tibet along the EHS3D-3 Profile from Xiachayu to Yushu including data acquisition, processing, inversion and interpretation. The effective period of the measured LMT signals extend from 10s up to 30000s for the duration more than one week measurement. The resulting model shows that the LMT sounding coincides with the MT data in overlapped periods. Especially the induction arrows and tippers derived from LMT data provide more information about the base of the conductors beneath the plateau with higher resolution. Anomalous induction coefficients and 2-D model suggest extensive conductive bodies beneath Lhasa block and Qiangtang terrain which would be a possible evidence for partial melt and fluids at depth.

青藏高原东部电性结构特征及其构造意义

Eastern Himalayan Syntaxis (EHS) and its surroundings (eastern margin of Tibet) is one of the most complicated tectonic areas in the world. As the exhaust opening of the balanced materials of the Tibetan Plateau during the collision of Indan and Eurasian plates, the deep structure beneath EHS surrounding region is referred to as the key to the study of the dynamics of the plateau. EHS3D project, sponsored by NSFC, has been proposed to explore the deep electric features of the area. During the first stage of EHS3D(2006-2008), MT+LMT measurements have been conducted along two lines from Chayu to Qingshuihe (EHS3D-3) and Chayu to Ruoergai (EHS3D-2). This paper will discuss the MT models of EHS3D-3 line. By the data procrssing, including distortion analysis, Robust estimation and strike decomposition, rotated apparent resitivities and phases have been obtained for each station. Then conventional 2-D inversion algorithms (NLCG and RRI) were employed to produce 2-D models. The final preferred 2-D model suggests that the upper crust consists of resistive blocks while in mid-lower crust there are two extensive conductive bodies beneath Lhasa block and Qiangtang terrain respectively. Jinshajiang suture is a gradient belt and Bangong-Nujiang suture appear a conductive belt dipping to the north. . We concluded that the formation of the two conductive bodies attributed to the partial melt and fluids in the lower crust. The regional electric strike derived from decomposition analysis indicates that the crust and upper mantle move in different manners. The upper crust moves like slips of rigid blocks along major slip faults while the lower crust creeps as a flow in the conductive channels.

华北及周边地区层析成像研究

Our study deals with the high resolution body wave tomography in North china and adjacent areas(30°N-43°N，100°E-130°E), where earthquakes occurred many times in history and has a very complicated geological structure. 6870 events recorded at 273 digital seismic stations from CDSN during 1996－2002 and stations settled by Seislab of IGCAS in Bohai Bay area, including 1382 local earthquakes and 5488 teleseismic earthquakes are used in this study. In the data we used, the average number of received stations is greater than 5, the error of picking up direct arrival time is 0.1－0.5s. Before the inversion, we use Checkerboard method to confirm the reliability of result of Local events; use Restoring Resolution Test to confirm the reliability of result of teleseismic events. We also analyzed the effect of different parameters in the inversion. Based the analysis above, the model used in this paper is divided into small blocks with a dimension of 0.33°in the latitude and longitude directions and 5km、15km、30km in depth, and initial velocity model. Using pseudobending method to calculate the ray traveling path, LSQR algorithm to inverse, finally, we got the body velocity images below 25km and above 480km in this area using Joint- inversion with local events and teleseismic events. We made the conclusion at last: (1)at top zone of the south of Sichuan Basin , there exits low velocity anomalies, below 40km is the high velocity zone extend to 300km; (2) Above the 40km of Ordos block exits low velocity zone, while below 40km until 240km, the high velocity anomalies are interlaced by low velocity anomalies. Below 300km, the anomalies are unclear any more; (3) On the whole, the velocity structure below 400km on the mantle transition zone of Eastern China area shows its changes from low velocity to high velocity.

基于三重震相波形模拟研究亚洲东北部上地幔过渡带速度结构

Both the global and regional P wave tomographic studies have revealed significant deep structural heterogeneities in subduction zone regions. In particular, low-velocity anomalies have been observed beneath the descending high-velocity slabs in a number of subduction zones. The limited resolution at large depths and possible trade-off between the high and low velocities, however, make it difficult to substantiate this feature and evaluate the vertical extent of the low-velocity structure. From broadband waveform modeling of triplicated phases near the 660-km discontinuity for three deep events, we constrained both the P and SH wave velocity structures around the base of the upper mantle in northeast Asia. For the two events beneath the southern Kurile, the rays traveled through the lowermost transition zone and uppermost lower mantle under the descending Pacific slab. Our preferred models consistently suggest normal-to-lower P and significantly low SH velocities above and below the 660-km discontinuity extending to about 760-km depth compared with the global IASP91 model, corroborating previous observations for a slow structure underneath the slab. In contrast, both high P and SH velocity anomalies are shown in our preferred models for the Japan subduction zone region, likely reflecting the structural feature of a slab stagnant above the 660-km discontinuity. The velocity jumps across the 660-km discontinuity were found to be on average 4.5% and 7% for P and S waves under the south Kurile, and 3% and 6% under the Japan subduction zone. The respective velocity contrasts in the two regions are consistent with mineralogical models for colder slab interior and hotter under-slab areas. Based on mineral physics data, the depth-averaged ~1.5% P and ~2.5% SH velocity differences in the depth range of 560-760 km between the two regions could be primarily explained by a 350~450K temperature variation, although the presence of about 0.5wt%~1wt% water might also contribute to the subtle velocity variations near the base of the transition zone in the southern Kurile. From our modeling results, we speculate that the slow structure in the southern Kurile may be correlated to the low velocity zone observed previously around the 410-km discontinuity under Northern Honshu. Both are probably associated with a thermal anomaly rooted in the lower mantle beneath the subduction zone in northeast Asia.

山东莒南地区韧性剪切带的变形特征与形成演化

Ju Nan of Shandong province is located at southwest of Sulu UHP (ultrahigh-pressure) metamorphic terrane. It is composed of gneiss, paragneiss, eclogites, ultramafic rocks, marble and quartzite. A large ductile shear zone extends east-west has been found at the Zhubian, The south of Junan county. The Zhubian ductile shear zone is composed of high srain rock and mylonites. The mylonites fall into 3 types: Initial gneiss mylonite, mylonite and altramylonit.obvious lineation of penetration,foliation,S-Cfabrics,porphyroclasts,folds,irregularundulatory,extinction,subgrain boundary, dynamic recrystallization microstructure, core-mantle structure and are common in the ductile shear zone. Based on field work and microstructural analyse, a conclution is arrived: The ductile shear zone is an approximately SE trending faults. The Zhubian ductile shear zone formed at Ep ―Hb facies conditions which could be proved by deformaed and metamorphosed mineral aggregates, Deformation behavior, Ternary-feldspar geothermometry and so on. Zircon MC―ICP―MS U-Pb analysis is performed on the mylonite and have an average age ―835.9±13.9Ma, it’s the primary rocks formed age. The Zhubian ductile shear zone maybe formed at 224-242Ma.

内蒙古克什克腾旗小东沟斑岩型钼矿床的成矿作用

In this paper, the Xiaodonggou porphyry molybdenum deposit located in the Xarmoron molybdenum metallogenic belt is chose as the research area. We have analyzed the petrology of the Xiaodonggou pluton in detail and made chemical analysis of the major and trace elements, Rb-Sr and Sm-Nd isotope, common lead isotope and SHRIMP zircon U-Pb dating et al; in the other hand, we use the molybdenite to make common lead analysis and Re-Os isotopic dating. The Xiaodonggou pluton is rich in silicon, potass, zirconium, and low in REE. In addition, it has no minus Eu abnormity and show a isotopic composition high in εNd(t) and low in Sri, indicating its magma origining from the melting of juvenile thicken lower crust. In the meanwhile, it contained the features of high temperature, quick melting, quick segregation and quick emplacement. The common lead analysis of the pluton orthoclase and molybdenite show that the former transfer from orogen to mantle and the latter come from mantle, which is consistent to the molybdenite sulfur isotopic and quartz oxygen isotopic composition, demonstrating that the rock and ore-forming materials of deposit having different sources, magma from the lower crust mixing with mantle fluid. In plus, we use the physical experiments results of the water-magma reaction to explain the interaction of magma and mantle fluid. In the deep crust, these two systems uplifted in a immiscible state; when they reached low depth, the stream film between fluid-magma collapsed, and the magma was broken into small agglomerates by the fluid, then they mixed thoroughly. The SHRIMP zircon U-Pb dating gave a result of 142±2Ma and the molybdenite Re-Os dating result is 138.1±2.8Ma, corresponding to the big tectonic transition period of 140Ma, when the major stress field changing from south and north to west and east. At this time, the Da Hinggan ling ranges area was under an extensive background, underplating proceeded and mantle materials could add into the magmas forming in the lower crust. So, from the above analysis, we propose the following model for the Xiaodonggou porphyry molybdenum deposit: in the early Cretaceous period, the Da Hinggan ling ranges area was under a extensive background, the adding of mantle fluid containing ore materials into heated lower crust made it melting to produce magmas. Following more mantle fluid got into the magma room and urged the magma to segregate from the source quickly. The fluid and magma uplifted together, when they arrived at shallow depth, the fluid-magma became unstable and the latter was broken into many small agglomerates with fluid connecting them in the interspaces. Because of the H+, K+ and various elements existing in the fluid, it would reacted with the magma and the rock through alteration and ore minerals crystallized out, forming the Xiaodonggou porphyry deposit with disseminated mineralization phenomenon.

喜马拉雅西构造结区岩石圈演化三维有限元动力学数值模拟

The past three decades have seen numerous attempts to numerically model stress and strain patterns in the lithosphere of the Earth on both global and regional scales. This efforts have been indispensable in identifying the features we need to include in our endeavour to develop better models of our planet’s lithosphere and they have also raised our awareness for the many unresolved issue in the deep geodynamical issues that need to be addressed in the future. Nonetheless, in most models, the lithosphere is treated as a single layer with depth-averaged properties, and as the same distribution in the stress and strain fields, and as deforming under plane strain. All these above make a great hander for its reality and degree of recognition. As the beginning in this paper, some principal numerical models and results on the evolution of Tibetan plateau are reviewed and analyzed. Then, the geological and geophysical expedition on the Western Himalayan Syntaxis is briefly reviewed. Furthermore, we analysis the feature in deep geophysical field studies in this area and adjacent regions. Because, for most continents, stress models driven by plate boundary forces have successfully reproduced the main characteristics of the stress and strain field, we present a set of three-dimensional models of lithosphere system for a simplified geometry of the Western Himalayan Syntaxis area and its adjacent regions, where we try to match the first-order characteristics of the stress and strain fields of lithosphere since 10 Ma, and deformation and geodynamical evolution process in former 2Ma. Of course, the kinematic boundary conditions of the stress models driven by plate boundary forces were applied. The rheology plays a significant role in the lithospheric tectonics, which lead to different rheological parameters were used in different works although the have the same constitutive equations in models. So, in this paper we do not aim to produce all characteristics of the Western Himalayan Syntaxis areas’ stress and strain fields by the choices of various parameters, but rather the dynamic response between various rheological parameters and stress and strain fields. We have chosen to concentrate on the importance of rheology and lateral strength variations for lithospheric stress and strain patterns and use our findings to build a model of the Western Himalayan Syntaxis areas. In doing so, we want to go beyond purely elastic models or purely viscoelastic models. Compared the results of the crust viscosity in the Western Himalayan Syntaxis areas, we believed that, when various viscoelastic models are adopted, the selection of the coefficient of viscosity in the Western Syntaxis area has important influence on the its uplifts and evolutions. A wider uplift ranges and gently elevation was observed at the same time when a lower viscosity was used in our models, and vice versa. Data of stress magnitudes are not available, but it is clear that the stress levels must be at or below the failure threshold of rock under compression. Under these criteria, the calculation results show that the viscosity in the Western Syntaxis area should be smaller than 1023Pa.s When elastic model is adopted in relatively rigid Tarim basin, obvious changes are induced to the stress and strain fields of the whole Western Syntaxis area. We found that rigid block of lithosphere reduced stress levels within its interior and that, at the edges of such regions, stress orientation can change. Furthermore there is no evidence that such rigid regions act as stress barriers in that they shield areas in opposite sides of the structure from the influence of one another. In our models, the upper crustal material of the Western Syntaxis area does not turns to move westward. Whereas, because of the stress and strain fields have been decoupling at the interior of the lithosphere, we can get the results that the deep material must not move westward.