首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
The Middle Devonian volcanic rocks in the northern area of East Junggar, located between the Ertix andUlungur rivers of northern Xinjiang, may be divided into basic and acid ones. It is evident that a compositionalgap exists between the two groups so that the volcanic rocks are not in line with a calc-alkaline series becausethe intermediate rocks are absent in the area. The fact shows that the volcanic rocks are a typical bimodal asso-ciation. The formation of the bimodal association of volcanic rocks in the area was closely related to continen-tal rifting or continental extension in the Middle Devonian. In such a tectonic setting, magmas were first pro-duced by partial melting of the mantle. Where crustal thinning was greater, the magmas ascended and eruptedon the surface directly so that the basic volcanic rocks formed, but olivine and/or partial pyroxenefractionation occurred in the magmas during their ascent through the thinning crust. On the other hand, wherecrustal thinning was less, ascending mantle-derived magmas reached the lower crust and accumulated there, re-sulting in partial melting of the lower crust and thus giving rise to the contaminated magma which was consoli-dated as acid volcanic rocks on the surface.  相似文献   

2.
The Aktubaik gold deposit lies in the Altay middle-high mountains area, Xinjiang, hosted by the Pa-laeo- and Mesoproterozoic Xemirxek Group. It is the first gold deposit found in Precambrian rocks in Altay. The deposit is controlled by the NW-trending fracture-alteration zone, in which rocks have been strongly altered and bleached. The main wall-rock alterations include silicification, sericitization (muscovitization), carbonation, pyritiza-tion and tourmalinization. Several gold mineralization zones of this type have been found in the study area. The dominant gold mineral is native gold, which is distributed very unevenly, so special methods such as peeling and bulk sampling are required in exploration. The discovery of this gold deposit has laid a foundation for gold exploration in Precambrian rocks in the Altay middle-high mountains area, Xinjiang.  相似文献   

3.
正1 Introduction Salt lakes are widely distributed in the world,and salt lakes in China are mainly located in the area of the Qinghai-Xizang(Tibet),and the Autonomous Regions of Xinjiang and Inner Mongolia.There are more than 700salt lakes,each with an area larger than 1 km2,in the  相似文献   

4.
<正>Pyramid's Arabic meaning"cone",it is a square bottom spire of stone building in Pyramid,the ancient Egyptian burial tomb of the king and queen are the most typical.Because of its grand scale,its sides are composed of plurality of triangular or triangular surfaces which are connected to the top,the area is very small,even a spire shaped,resembling Chinese characters in"gold"word,so  相似文献   

5.
The present study focuses on building a workflow for structural interpretation and velocity modeling and implementing to Jurassic-Cretaceous succession (Chiltan Limestone and Massive sand of the Lower Goru Formation). 2D-Migrated seismic sections of the area are used as data set and in order to confirm the presence of hydrocarbons in the study area, P and S-wave seismic velocities are estimated from single-component seismic data. Some specific issues in the use of seismic data for modeling and hydrocarbon evaluation need to deal with including distinguishing the reservoir and cap rocks, and the effects of faults, folds and presence of hydrocarbons on these rocks. This study has carried out the structural interpretation and modeling of the seismic data for the identification of traps. The results demonstrate existence of appropriate structural traps in the form of horst and grabens in the area. 2D and 3D velocity modeling of the horizons indicates the presence of high velocity zones in the eastern half of the study while relatively low velocity zones are encountered in the western half of the area. Two wells were drilled in the study area (i.e. Fateh-01 and Ichhri-01) and both are dry. Immature hydrocarbons migration is considered as a failure reason for Fateh-01 and Ichhri-01 well.  相似文献   

6.
Water resources system is composed of natural water subsystem and social water subsystem. And it is a complicated large system, which contains certain regional background, as well as specific framework, function and dynamic balance. The evaluation of the water resources system needs the viewpoint of sustainable development and the measurement according to water resources system carrying capacity, which holds the meaning of both water resources carrying capacity and water environment carrying capacity. The Changjiang River Delta is a very important area in China. As the local water resources are concerned, the Delta is an area lack of water as a matter of fact. The water resources system of the Delta experiences a long, intricate and degenerate period. The lack of water due to resources shortage in the 1950＇s was converted to that due to water quality from the 1980＇s. Furthermore, the status of water shortage sharpens gradually. The representations are summarized as follows： firstly, the discharge amount of wastewater and polluted water is large all along. Secondly, the pollution status of rivers, which involve the Changjiang River, the Grand Canal, the rivers in cities and the rivers in small towns and villages, is noticeable. Thirdly, water quality of Taihu Lake is worth of more attention. Therefore, the countermeasures on the reconditioning and regulating of water resources system in the Delta demands the following new strategies, such as to treat the rivers, the lakes and the seas as one overall system, to improve, harmonize and counterpoise water resources system carrying capacity, to implement the integrated management of water resources, which means the integrated management of drainage area along with the regional area, especially the integrated management of city water, and to carry on water saving and scientific use so as to increase the efficiency of water use, and so on.  相似文献   

7.
After the establishment of the global stratotype section and point (GSSP) of the Permian-Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian-Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcoming:(1) the exact TPTB horizon is difficult to define paleontologically with high-resolution, and (2) accurate correlation between marine and terrestrial PTBs in hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic-Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well-developed, allowing bed-to-bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high-resolution demarcation of the TPTB. These features fund in estern Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.  相似文献   

8.
The Lower Yangtze region is one of the important marine sedimentation areas of oil and gas distribution in southern China,for its favorable source rocks,reservoirs and covers.However,the intense tectonic movements and complex hydrocarbon generation process made it highly impossible to form large-sized oil and gas reservoirs.So it was divided to different hydrocarbon-bearing preservation units in oil-gas exploration.Recent study shows that the Permian and Lower Triassic source rocks in the Lower Yangtze region are complicated in lithology.The hydrocarbon generation potential of limestone there is low while argillaceous source rocks are overall of high abundance with excellent organic types,now in the process of hydrocarbon generation,so differences in high maturity influence the evaluation of organic matter abundance and type.Biomarker characteristics indicate a reductive environment.n-alkanes are marked by a single peak,with no odd-even predominance.The composition and distribution of the carbon numbers of n-alkanes,and the high abundance of long-chain tricyclic terpanes are indicative of marine sedi-mentation.The high contents of pregnane,homopregnane,rearranged hopane suggest that the source rocks are of high maturity.There is a good linear correlation between methylphenanthrene index and vitrinite reflectance.The correlation of oil-source rocks indicated that the oil of Well HT-3 may come from the Permian Longtan Formation in the Huangqiao area,the oil of Wells Rong-2 and Juping-1 came from the Lower Triassic Qinglong Formation in the Jurong area.The exploration here is promising in those different source rocks which all have great potential in hy-drocarbon generating,and oil and gas were produced in the late stage of hydrocarbon generation.  相似文献   

9.
The identification of unconformities is the key to reconstructing tectonic evolution, revealing crust movement and establishing tectonic cycle. For a long time, there were some controversial issues on the episodes of Variscan cycle (especially on the period of Carboniferous-Permian stages) of the Tianshan area. The essential questions fall on the numbers and property of unconformities in this area, for example, in the western Tianshan area. Previous research only recognized three or four fold movements. Detailed regional geological mapping of 1:50000 in the Tekes Daban area, western Tianshan have allowed us to characterize the seven unconformities within the Carboniferous-Permian strata and understand its implications for tectonic reconstruction of the Tianshan orogen. Seven angular unconformities, which indicate that seven tectonic episodes occurred in the Late Paleozoic Period, were identified in this area. Therein, the newly discovered unconformities based on the angle-unconformity between the Dongtujinhe and Keguqinshan Formations, and angle-unconformity between the Wulansayi and Wulang Formations, respectively indicates the Tekes episode and Gongliu episode. The unconformity between the Dongtujinhe and Yishijilike Formations is angle-unconformity instead of parallel unconformity indentified by previous research, so the former Bogda ascending can be revised as Bogda movement. Therefore, these newly identified seven episodes, including the Tekes episode, suggest that there are seven tectonic movements in the Tianshan area at least. This has significant implications for reconstruction of the Late Paleozoic tectonics in the Tianshan Area, NW China  相似文献   

10.
Silver occurs in South China wolframited-quartz veins in three forms:(1)as micro inclusions of Ag2S and AgBiS2,(2) as argentite and matildite as a result of exsolution and(3)as Ag-bearing sulfosalts and independent silver minerals.According to mineral assemblaged the Ag-bearing tungsten deposits are classified as two types:(1)Ag-bearing W-Bi deposits in eastern Nanling,where gustavite has been found and（2）Ag-bearing W-Sn(Sb)deposits which are mainly distributed in western Nanling.The authors consider that the enrichment of silver and sulfosalt minerals in the lower parts of pneumato-hypothermal tungsten deposits is the result of reversed vertical zoning caused by high concentrations of F and S in the ore-forming fluids.  相似文献   

11.
This paper takes the South Yellow Sea as an example to show a new method for comprehensive geological-geophysical research such as residual basin and tectonolayering using airborne gravity and magnetic data in China. Based on airborne gravity and magnetic data, by measuring and analyzing stratigraphic density and susceptibility, the depths to the pre-Sinian magnetic basement top, the pre-Jurassic top and the Cenozoic bottom, are obtained by forward and inverse methods constrained by seismic and drilling data; and furthermore, the residual thicknesses of the Sinian–Triassic, the Jurassic–Cretaceous and the Cenozoic are calculated. Based on airborne gravity and magnetic anomalies, the faults in the pre-Sinian magnetic basement, the Jurassic-Cretaceous and the Cenozoic are respectively interpreted by the qualitative and quantitative methods. On the basis of the above study, and combining regional important tectonic events, four tectonolayers are divided in the vertical succession in South Yellow Sea, namely the pre-Sinian magnetic basement, the Sinian-Triassic, the Jurassic-Cretaceous and the Cenozoic. The result shows that there are thick Cenozoic and Jurassic-Cretaceous strata and thin residual Sinian-Triassic strata in the Suzhong-Huangnan depression area, but there are thin or only sporadic Mesozoic-Cenozoic terrestrial strata and thick Sinian-Triassic marine strata reserved in Subei-Huangzhong uplift area and Sunan-Wunansha uplift area. The four tectonolayers are very different in structures as well as distributions in plane.  相似文献   

12.
Two sequences can be identified in the sedimentary strata of the lower Tertiary ShahejieFormation in the Zhanhua hollow. The lowstand, lake-transgressive and highstand systemstracts were formed under the control of ancient structure, palaeotopography, palaeoclimate, sed-iment supply, marine-transgression, and so on. In the paper the authors present a composite se-quence stratigraphical section of the Shahejie Formation in this area, and expound the bounda-ries of parasequences, parasequences set and systems tracts and evolutions of lake sequencestratigraphy and sedimentology and discuss various factors controlling the lake level fluctuation.The differences between lake and marine sequence stratigraphy are also indicated in the paper.The lake sequence stratigraphical study should be based on a synthetic analysis of structural evo-lution, palaeomagnetism, palaeoclimatic changes, geological Well logs, seismic and logging data,palaeontological data, global sea level changes, and so on. The sequence stratigraphical evolutionis closely related to the formation, development and elimination of the whole basin and thesedimentary process.  相似文献   

13.
The airborne gravimetry was an important leap and innovation in the world’s history of geophysical exploration. China's first test of the airborne gravity geological survey in the onshore-offshore transitional area of the western and southern part of the Bohai Sea was successful and effective in geology. Based on the airborne gravity data, and combining previous ground gravity, seismic and drilling data etc., we carried out the geological interpretation by forward and inverse methods. The result shows that the airborne Bouguer gravity anomaly was clear, the fracture interpretation was reliable, and the inversion depth of the main geological interfaces was relatively accurate. This airborne gravity geological survey not only filled the exploring gaps in the onshore-offshore transitional area, and realized the geological and tectonic junction between the sea and the land, but also discovered four local gravity anomalies, 11 fractures and three sags or subsags, and so on. The good geological effect of airborne gravimetry not restricted by terrain condition shows that it can be served as a new geophysical method in the exploration of complex terrain physiognomy area such as mountain, jungle, desert, marsh, onshore-offshore transitional area and so on, and has an extensive application prospect in China in the future.  相似文献   

14.
V.N. Makarov 《冰川冻土》2004,26(Z1):257-262
Placer diamond mining in the Anabar area involves various operations that cause long-term (nearly a quarter of a century) environmental impacts. The long history of mining activities, the technology used to mine the placers, as well as the poor assimilative capacity of the natural systems can result in serious environmental impacts in the area. The primary geochemical processes in the diamond-bearing area are affected by the occurrence of permafrost and relict ice, the lengthy duration of ice cover in water bodies, and the widespread development of cryogenic processes. This promotes physical migration of contaminants, cryogenic metamorphization of waters, and long-term accumulation of organic contaminants in low-temperature, reduction and sedimentation barriers. In this paper, some environmental and geochemical effects of diamond mining in the Arctic area are discussed.  相似文献   

15.
The karst area accounts for 61.9% of the total area in Guizhou Province, which gives rise to a fragile environment and backward economy. Comparative studies on the element contents of rock and soil and agriculture production in both carbonate area and non-carbonate area have been made to establish factors leading to low output and poor quality of agricultural products in the karst area. The result shows that there is an apparent lack of nutrient elements in carbonate rocks. The trace element contents of carbonate rocks are only 3532.27×10-6, but those of non-carbonate rocks are 10894.21×10-6. The available element contents in culti-vated soil delivered from carbonate rocks are merely 101.4×10-6, but those from non-carbonate rocks are 326.05×10-6. The available element contents and total element contents in cultivated soil delivered from non-carbonate rocks are 3 times higher than those from carbonate rocks. Besides, high-quality agricultural products such as rice, potato and tea are mainly produced in the non-carbonate area. It is indicated that the low output and quality of agricultural products are caused by the above-mentioned low trace element contents and poor agricultural environment. Therefore, a new method of mineral nutrients compensation has been put forward, which is very effective to raise the load-bearing capacity of agricultural environment, agricultural output and quality of agricultural products.  相似文献   

16.
A study of faults and their control of deep gas accumulations has been made on the basis of dividing fault systems in the Xujiaweizi area. The study indicates two sets of fault systems are developed vertically in the Xujiaweizi area, including a lower fault system and an upper fault system. Formed in the period of the Huoshiling Formation to Yingcheng Formation, the lower fault system consists of five fault systems including Xuxi strike-slip extensional fault system, NE-trending extensional fault system, near-EW-trending regulating fault system, Xuzhong strike-slip fault system and Xudong strike-slip fault system. Formed in the period of Qingshankou Formation to Yaojia Formation, the upper fault system was affected mainly by the boundary conditions of the lower fault system, and thus plenty of multi-directionally distributed dense fault zones were formed in the T2 reflection horizon. The Xuxi fault controlled the formation and distribution of Shahezi coal-measure source rocks, and Xuzhong and Xudong faults controlled the formation and distribution of volcanic reservoirs of Y1 Member and Y3 Member, respectively. In the forming period of the upper fault system, the Xuzhong fault was of successive strong activities and directly connected gas source rock reservoirs and volcanic reservoirs, so it is a strongly-charged direct gas source fault. The volcanic reservoir development zones of good physical properties that may be found near the Xuzhong fault are the favorable target zones for the next exploration of deep gas accumulations in Xujiaweizi area.  相似文献   

17.
There is a controversy regarding the amalgamation of Xing'an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS) in the eastern Central Asian Orogenic Belt(CAOB). To solve this problem, we performed detailed study on the granites from the Zhangdaqi area, adjacent to the north of the HHS in the northern part of the Great Xing'an Range, NE China. Geochemically, the granites in the study area are metaluminous-weak peraluminous and high-K calc-alkaline series. Trace elements of the granites show that LREEs are relatively enriched, while HREEs are relatively deficient and obvious REE fractionation. The granites are characterized by obvious negative Eu anomalies, meanwhile, they are relatively enriched in Rb, K, Th and depleted in Ba, Nb, Sr, P, Ti. All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A-type granites. The zircon LA-ICP-MS U-Pb ages of these granites are 294–298 Ma, indicating that they formed in the Early Permian. These granites also have positive ε_(Hf)(t) values(8.4–14.2) and a relatively young two-stage model age between 449 Ma and 977 Ma, implying that the magma was derived from the re-melting of the Early Paleozoic-Neoproterozoic juvenile crust. Combined with geochemical characteristics(Nb/Ta ratios of 9.0–22.2, and Zr/Hf ratios of 52.3–152.0), we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle. A-type granites and bimodal volcanic rocks along the Hegenshan-Heihe Suture formed during the Late Carboniferous-Early Permian, indicating that the HHS between Xing'an and Songnen Blocks closed in the late EarlyCarboniferous. Subsequently, the Zhangdaqi area was in a post-orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A-type granites.  相似文献   

18.
Dinggye lies in the middle part of the Himalayan Orogen. A lot of low angle extension detachment faults have been developed in Dinggye area and some of them make up the main body of the South Tibet Detachment System. On the whole, the extension direction of all the detachment faults is perpendicular to the strike of the Himalayan Orogen. Each detachment fault has its distinct characteristics. Mylonite was extensively developed in the detachment faults and can be divided into a variety of types such as siliceous mylonite, felsic mylonite, granite mylonite, protomylonite, crystallization mylonite and so on. On the basis of our field survey works, these detachment faults can be classified according to their locations into three units listed as follows: (1) In the northern part of the study area, the detachment faults occur on large scale and in orbicular shape, and form the middle layer of the metamorphic core complexes. (2) In the southern part of the study area, the detachment faults occur in linear shape that is parallel to the Himalayan Orogen and has a stable attitude, and have undergone two phases of development. In the first phase, the Rouqiechun Group rocks were formed and make up the hanging wall, while in the second phase the Jiachun Group rocks were formed and make up the hanging wall. (3) In the southeastern part of the study area, the detachment faults strike nearly along southeast direction in a stable way and some of these detachment faults were distorted by the late-formed faults and folds. Furthermore, in the southwestern part of the study area, the ductile shear zones are parallel to the detachment faults.  相似文献   

19.
There are many thrust-related structures occurring in the Paleozoic strata of the Niushou Mountain in the central part of Ningxia Hui Autonomous Region. The fault-related folds are the typical structures in this area. Based on the analysis about these structures and their relationships, the processes by which these structures of the Miboshan Formation were formed are reconstructed, and the strata underwent about three stages of deformation: (1) horizontal shortening, (2) folding, and (3) thrusting. And the fact that the Niushou Mountain is the leading edge of an old thrust sheet was proved, the Niushou Mountain, the Daluo Mountain and the Xiaoluo Mountain together constitute the front part of this old thrust zone, so the Niushou Mountain and the Ordovician strata in the central and southern parts of Ningxia now are likely allochthons. In the period from middle Ordovician to Devonian, the areas of the central and southern Ningxia belonged to the back-arc foreland basin of North Qilianshan orogen, which was adjacent to the continent in the north. In the later part of the early Paleozoic period, the Niushou Mountain was formed after the closure of the back-arc foreland basin.  相似文献   

20.
Natural gas exploration in Nanpu sag, Bohai Bay Basin, has achieved breakthroughs in recent years, and a number of natural gas and condensate wells with high yield have been found in several structures in the beach area. Daily gas production of single wells is up to 170,000 m3, and high-yield wells are mainly distributed in?the Nanpu No. 1 structural belt.?Studies have shown that these natural gases are mainly hydrocarbon gases, with methane content about 80% to 90% and ethane 6%-9%, so they are mainly wet gas; and non-hydrocarbons are at a low level.?Carbon isotopes of methane range from -42‰ to -36‰, and ethane from -28‰ to -26‰. Calculated maturity based on the relationship between δ13C and Ro of natural gas, the gases are equivalent to those generated from organic matter when Ro is 1.0%-1.7% (mainly 1.25%-1.32%). The natural gas is oil-type gas generated from the source rocks at mature to high mature stage, associated with condensate, so carbon isotopes of the gases are heavier. Natural gas in the Nanpu No.1 structural belt is mainly associated gas with condensate. The analysis of the origin and source of natural gas and condensate, combined with the monomer hydrocarbon carbon isotopes and biomarker, indicated that the main source rocks in the Nanpu No.1 structural belt were Es3 (the lower member of the Shahejie Formation), followed by Es1 (the upper member of the Shahejie Formation).?The high-mature hydrocarbons from source rocks in the deep sag mainly migrated through deep inherited faults into shallow traps and accumulated to form oil and gas pools. Therefore, there is a great potential for exploring gas in deep layers.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号