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1.
青藏高原新生代火山岩矿物化学及其岩石学意义   总被引：10，自引：1，他引：9  
《矿物学报》1999,19(2):2
This paper deals with the features of mineral chemistry about olivine, pyroxene, feldspar, sanidine megacryst and garnet megacryst from Cenozoic volcanic rocks, Qinghai-Tibet plateau. The forming condition including temperature and pressure of the volcanic rock series is also studied. The results show that olivine belongs to forsterite (Fo=81—85) and clinopyroxene is rich in TiO2 (1.06%—1.74%). Especially the sanidine megacryst is optical homogeneous. There are not zonal texture, exsolution texture and twin crystal. It is low in ordering degree and belongs to K-sanidine. The garnet megacryst mainly consists of Alm and Pyr, which crystallization depth resembles the depth of middle crust. The mineral chemistry, major element and isotopic features indicate that of the Cenozoic volcanic rocks in the north part of the Qinghai-Tibet plateau mainly consists of shoshonite series formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust-mantle mixed belt.  相似文献   

2.
Developed in the Mt.Kunlun orogenic belt at the northern margin of the Tibetan Plateau is an active Cenozoic volcanic zone which is more than 1000km in length and some ten to hundred kilometers in width.It extends east-westwards and is roughly parallet to the strike of Mt.Kunlun.The Cenozoic volcanic rocks are divided into the northern(N-)and southern(S-)subzones.Eruptions of volcanic lavas in the S-subzone are related to an initial rift zone within the north Qiangtang terrane,but the volcanic rocks in the N-subzone are relatively close to the contact zone between the Mt.Kunlun and the Tarim terrane.The space-time distribution,petrological and geochemical features can be explained by a model of southward intraplate subduction of the Tarim terrane.  相似文献   

3.
Neogene volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, are represented by a typical intermediate-basic and intermediate alkaline rock association, with latite-trachyte as the main rock type. The results of chemical analysis are: SiO2=52%–62%, Al2O3>15%, Na2O/K2O>1 and MgO<3.30%. In addition, the volcanic rocks are LREE-enriched with LREE/HREE=10–13, (La/Yb)N=15–19, and show a weak negative Eu anomaly with δEu=0.71–0.89. The close relationship between Mg# and SiO2 and the co-variation of the magmatophile elements and ultra-magmatophile elements such as La/Sm-La and Cr-Tb indicate that this association of volcanic rocks is the product of comagmatic fractional crystallization. The rock association type and lower Sm/Yb values (Sm/Yb=3.23–3.97) imply that this association of volcanic rocks should have originated from partial melting of spinel lherzolite in the lithospheric mantle. On the other hand, the weak negative Eu anomaly and relative depletion in Nb, Ta and Ti reflect the features of terrigenous magma. So the Neogene Belog Co alkaline volcanic rocks should be the result of partial melting of the special crust-mantle transition zone on the Qinghai-Tibet Plateau.  相似文献   

4.
Tengchong Cenozoic volcanics that have record key information on the tectonic evolution and mantle features of the southeast margin of the Tibetan Plateau are of great importance because of its unique eruption history spanning the entire Quaternary period. Magma origin and evolution of Tengchong Cenozoic volcanic rocks were studied on the basis of Nd-Sr-Pb isotope and major and trace element data from different eruptions in the Ma’anshan area. Different samples within one eruption show relative identical lithologies, chemical and isotopic compositions. However, the geochemical features for the five eruptions are distinct from each other. These volcanic rocks show low Mg# values (<45), moderate to high fractionation of LREEs and HREEs, and enrichment of Pb and Ba and depletion of Nb. Tengchong Cenozoic volcanic rocks were derived from an enriched mantle based on Nd-Sr-Pb isotopic studies. And lines of evidence show that crustal contamination should be involved before the eruption of different periods of Tengchong Cenozoic volcanic rocks. Older subducted components may be responsible for adakite recycling at various stages of evolution, which results in the origin of the enriched mantle source magma accounting for the isotopic features of Tengchong Cenozoic volcanic rocks. Segregated primitive magma pulsating injected into magma chamber, fractional crystallized and contaminated with crust component. Finally, magmas with distinct chemical and isotopic compositions for each eruption formed. The extension of the northeast segment of the Yingjiang tectonic belt triggered the pulsating eruption of the Cenozoic volcanics in the Tengchong area.  相似文献   

5.
The Pulang porphyry copper deposit is located in the Zhongdian island arc belt, NW Yunnan, in the central part of the Sanjiang area, SW China, belonging to the southern segment of the Yidun island arc belt on the western margin of the Yangtze Platform. In the Yidun island arc, there occur well-known "Gacun-style" massive sulfide deposits in the northern segment and plenty of porphyry copper deposits in the southern segment, of which the Pulang porphyry copper deposit is one of the representatives. Like the Yulong porphyry copper deposit, this porphyry copper deposit is also one of the most important porphyry copper deposits in the eastern Qinghai-Tibet Plateau. But it is different from other porphyry copper deposits in the eastern Qinghai-Tibet Plateau (e.g. those in the Gangdise porphyry copper belt and Yulong porphyry copper belt) in that it formed in the Indosinian period, while others in the Himalayan period. Because of its particularity among the porphyry copper deposits of China, this porphyry copp  相似文献   

6.
The Cenozoic evolution history of Guizhou Province, which is located on the southeastern flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesi  相似文献   

7.
正Objective The East Kunlun Orogenic belt constitutes the first marked change in the topographic reliefs north of the Qinghai-Tibet Plateau.The Cenozoic tectonic evolution of this orogenic belt is crucial for understanding the remote deformational effects of the Eurasian plate collision and the migration track at the northern margin of the plateau.However,when and how the uplift occurred remains  相似文献   

8.
Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect co  相似文献   

9.
Abstract: The Shijuligou deposit was separated by an arcuate ductile shear zone cross the center of the deposit region, resulting in the difference between the southern and northern ore bodies. The lead (Pb) isotopic data of ores of the Shijuligou copper deposit have averages of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in 17.634, 15.444, and 37.312, respectively. It has been shown that ore-forming metals originated from intrusive and extrusive rocks in the upper part of ophiolites. The sulfur isotopic data of pyrite and chalcopyrite in the northern part change from +7.61‰ to +8.09‰ and +4.95‰ to +8.88‰ in the southern part. Isotopes of δ18O in the Shijuligou copper deposit are between +11.1‰ and +18.6‰, with the calculated δ18OH2O at +0.65‰. It is suggested that the mineralized fluid is a mixture of magma fluid, meteorological water, and seawater through circulating and leaching metals from the volcanic rocks. The zircon uranium-lead (U–Pb) dating of gabbro is 457.9±1.2 Ma, and the lower crossing age of the discordant and concordia curves of pyroxene spilite of zircon is 454±15 Ma. It is indicated that the Shijuligou deposit formed in a new ocean crust (ophiolite) of the back-arc basin in the late Ordovician. Mineralization should occur in the intermittence period after strong volcanic activity, and the age should be the late Ordovician. Moreover, the mineralization of ophiolite-hosted massive sulfide deposits in the ancient orogenic belt of the late Ordovician in the northern Qilian Mountains was controlled by the primary fault/fracture, with the forming of a metallogenic hydrothermal system by a mixture of volcanic magma fluid and seawater, which circularly leached the metallogenic metals from the volcanic rocks, resulting in their accumulation. The ore bodies were transformed with morphology and metallogenic elements. Jasperoid is an important sign for prospecting such deposits. There were many island arcs in the continent of China. This study provides evidence for understanding and exploration of ophiolite-hosted massive sulfide deposits in western China, especially in the area of northern Qilian Mountains.  相似文献   

10.
1. IntfoductionThe eastern Guangdong province is located in the southern part of the NE trending Chinacoastal volcanic belt and also is the intersection part of the E-W trending Namingtectonic-magmatic belt. Mesozoic orcks and intrusive rocks (dominated by acidic) widelycrop out over the area. The outcrop area of the intrusive rocks is l/2 of the whole district,and that of the volcanic rocks is 1/4 of the magmatic rocks formed in Yanshanian. Only afew of basic stocks and pillars formed in …  相似文献   

11.
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen.  相似文献   

12.
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.  相似文献   

13.
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″.  相似文献   

14.
东濮凹陷北部沙三中亚段广泛发育盐岩和烃源岩,这两个看似不能共存的物质却在这里互层共生。该时期研究区沉积特征为多盐韵律与多层烃源岩互层共生、连续沉积,单个盐韵律厚度从几米到十几米,烃源岩有机质丰度高、类型好。平面上,两者在湖盆沉积沉降中心共生;垂向上,高有机质丰度、好干酪根类型与高盐度地层具有较好的对应关系。因而成为恢复古气候和古环境的重要研究对象。通过岩石学、古生物学以及Sr/Ba、B/Ga、(V+Ni+Mn)、Fe/Mn、Sr/Cu、Mg/Ca、V/(V+Ni)、稀土元素含量和氯同位素等方法对凹陷北部沙三中亚段的沉积环境进行研究。结果表明,凹陷北部沙三中亚段为深水沉积的还原环境,古盐度较高,达到半咸水-咸水沉积;微量元素和孢粉化石特征表明研究区沙三中亚段为温暖潮湿的环境。  相似文献   

15.
Important tendencies in development of the world mineral-resources sector at the beginning of the 21st century were an increase in production and consumption of mineral materials differentiated by types of metals and nonmetallic mineral raw materials, by countries and regions, as well as the concentration of the production of mineral raw materials in a small number of countries, and a reduction in industrial reserves of minerals in the world economy, even at the current stage of their extraction. These tendencies should be taken into account in working out a strategy for development of the Russian mineral raw-material base.  相似文献   

16.
Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators.  相似文献   

17.
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18.
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19.
郯庐断裂南段研究进展与断裂性质讨论   总被引：13，自引：3，他引：13  
据1：5万区域地质调查和专题研究资料，就郯庐断裂带是否南延与消失的原因，其与大别—苏鲁造山带交截形成的假位错效应，以及与中新生代沉积盆地形成演化的关系等作了新的阐述。在此基础上，讨论了郯庐断裂带是否为巨大的左行平移断层或转换断层。认为郯庐断裂带可能是在“古郯庐带”的基础上于早侏罗世重新活动、白垩纪强烈活动的地堑型枢纽断裂带。  相似文献   

20.
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning.  相似文献   

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