共查询到20条相似文献，搜索用时 15 毫秒
1.
New data on geochemical features of the Lower Paleozoic terrigenous rocks in the Mamyn terrane (eastern Central Asian Fold Belt) and U–Pb geochronological studies of the detrital zircon from these rocks are presented. The obtained results suggest the following conclusions. 1. At present, the Kosmataya sequence includes different age Lower Cambrian terrigenous–carbonate and Lower Ordovician terrigenous rocks or represents Lower Ordovician olistostromes including limestone blocks with the Lower Cambrian fauna. Lower Ordovician terrigenous rocks were formed in an island arc or active continental margin, mainly, owing to the erosion of Cambrian–Early Ordovician plutons and volcanics that are widespread in structures of the Mamyn terrane and weakly reworked by the chemical weathering. 2. The Silurian Mamyn Formation was developed at a passive continental margin. The main sources of clastic material for this formation were the same Cambrian–Early Ordovician igneous rocks as for the Cambrian sequence, with the participation of Early Silurian and Vendian igneous complexes. The obtained data significantly refine concepts about the geological structure of the Mamyn terrane, which is a member of the Argun Superterrane, one of the largest tectonic structures in the eastern Central Asian Fold Belt. 相似文献
2.
According to Sm-Nd isotopic-geochemical studies, the t Nd(DM) of the terrigenous rocks of the Turan Group of the Bureya terrane is 1.4–1.5 Ga and their sources are Precambrian rocks and (or) younger effusive rocks, the formation of which is related to the reworking of the Late Precambrian continental crust. The U-Pb LA-ICP-MS geochronological studies indicate dominant Vendian-Cambrian (588–483 Ma) and Late Riphean (865–737 Ma) detrital zircons. Our data point to their accumulation at the beginning of the Paleozoic rather than in the Precambrian as is accepted in modern stratigraphic schemes. 相似文献
3.
内蒙古阿拉善北部杭乌拉地区位于中亚造山带的中段南缘,处于西伯利亚板块、塔里木板块和华北板块之间,是研究中亚造山带和古亚洲洋演化的重要区域。文中以杭乌拉地区硅质岩地球化学特征为主要研究内容,结合前人研究结果,对阿拉善北部地区早古生代构造背景进行分析。杭乌拉地区下古生界西双鹰山组和班定陶勒盖组硅质岩镜下可见黏土、陆源粉砂和放射虫等,表现为明显的沉积成因特征。硅质岩地球化学特征一致性较差,其中Fe、Mn、Al等主量元素、Sc/Th值、(La/Ce)n值和δCe值反映出硅质岩为大陆边缘沉积,(La/Yb)n值反映硅质岩接近于远洋沉积背景,δEu 值表现为无热液作用影响,V、V/Y、Ti/V值多接近于洋中脊和大洋盆地硅质岩特征,U/Th、Ba/Sr值也属于热水成因硅质岩特征。硅质岩稀土元素配分曲线呈平坦状,无明显的右倾(大陆边缘轻稀土元素富集配分模式)和左倾(开放洋盆重稀土元素富集配分模式)特征。研究区早古生代地质记录相对较少,但是鉴于该地区晚古生代复杂的构造演化特征及其对早古生代古地理格局的继承,并结合上述硅质岩地球化学特征,认为研究区在早古生代为一个多岛洋环境。 相似文献
4.
研究区位于准噶尔成矿省巴尔鲁克山—三塘湖晚古生代、中生代Cu、A u成矿带东段,构造上属唐巴勒-卡拉麦里古生代复合沟弧带。出露地层主要为奥陶系中酸性火山岩、火山碎屑岩及正常碎屑岩组合,泥盆系陆源碎屑岩、火山岩及火山碎屑岩组合,及石炭系正常碎屑岩夹火山碎屑岩组合。研究区侵入岩主要形成于华力西晚期,表现为从基性到酸性演化的特征。区内断裂和褶皱构造发育,为成矿提供了空间。笔者主要是通过对巴里坤县八墙子一带A u、Cu等元素在各个地层单元、侵入岩及构造中的分布特征研究,结合区内已发现的金、铜矿床、矿（化）点及异常的分布特征,总结了研究区金、铜矿成矿规律及找矿方向,认为区内金、铜矿产的形成与大地构造环境、区域构造以及岩浆活动有直接的关系。 相似文献
5.
V. I. Belousov 《Geotectonics》2007,41(5):392-402
The Upper Paleozoic preflysch sedimentary rocks in the Türkstan-Alay ranges are combined in a common section with limestone of autochthon and synsedimentation carbonate nappes, thus forming the upper-most layers of the stratigraphic section of the latter. By their lithology, relatively small thickness, facies variability, and position at the boundary between carbonate and flysch-olistostrome sequences (in the autochthon), these rocks correspond to a certain extent to preflysch of the Urals and the Mediterranean Alpine Belt. This association of clayey, carbonate, and terrigenous rocks is strictly constrained in stratigraphy (the upper portion of the lower Moscovian substage and the lower portion of the upper Moscovian substage) and localization (the southern slopes of carbonate platforms). The formation of this rock association immediately predated the Late Paleozoic overthrusting and deposition of terrigenous flysch. In paleotectonic terms, preflysch is an indicator of the initial stage of tectonic and magmatic activation that led to the replacement of carbonate sedimentation with deposition of terrigenous and clayey sediments, coeval volcanism, and stratiform ore formation. The following sequence of events has been outlined in the Early and Middle Carboniferous: (1) thrusting of volcanic-sedimentary rocks filling troughs over the northern margins of carbonate platforms, (2) lateritic weathering and deposition of marine bauxite in the Bashkirian and early Moscovian, (3) repeated overthrusting and deposition of preflysch on southern slopes of platforms, (4) invasion of the frontal flysch trough from the south, (5) scouring of preflysch and the underlying limestone, and (6) formation of flysch-olistostrome sequences and tectonic and gravity nappes in the late Moscovian time. This interpretation takes into account the southward vergence of thrust sheets and nappes, the structure and localization of allochthonous fragments of marginal zones of carbonate platforms, and the pre-Bashkirian thrusting of volcanic and sedimentary rocks over the condensed pelagic deposits of the Shalan Group. It is suggested that bauxite and preflysch materials had the same source and were deposited in the Middle Carboniferous on the offshore carbonate shoals. 相似文献
6.
Source rocks are present in all the stratigraphic units of the Mesozoic-Cenozoic deposits of the Turkmen shelf in the Caspian
Sea. The highest source rock potential is characteristic of I terrigenous and carbonate-terrigenous rocks of Middle Jurassic
age, and the Aptian, Paleogene, Neogene and Apsheron stages of the Quaternary system. To reveal the formation conditions of
hydrocarbon deposits within Southwestern Turkmenistan, the principle of chemical thermodynamics is primarily used via the
calculation of the free energy of gaseous hydrocarbons. This showed that hydrocarbon deposits within the topmost depositional
complex (the red-colored strata of the Middle Miocene at the Akchagyl and Apsheron stages) are syngenetic; their formation
was due to lateral migration from even-aged deposits from depression zones neighboring the uplifts. 相似文献
7.
Study of the element composition of ten samples of modern terrigenous and carbonate sediments from the northern part of the Caspian Sea by the ICP-MS method showed that these sediments were enriched in sulfur, nonferrous metals, and some related minor elements including Se, Te, Re, and others in comparison with the average composition of sedimentary rocks. It is assumed that local hydrothermal seeps similar to those known on the Cheleken Peninsula and which may be formed in other areas of this tectonically active zone are the sources of these elements. In addition, such a composition of sediments may indicate the sporadic contamination of bottom water with hydrogen sulfide, which has been observed in areas of the South and Middle Caspian by many researchers. 相似文献
8.
V. G. Popov 《Lithology and Mineral Resources》2000,35(4):365-372
This work treats lithofacies and hydrogeochemical features of the Late Paleozoic sedimentation on the eastern Russian Plate
and the geochemistry of principal types of brines, which are spatially and genetically related to halogenous formations. It
is shown that the density convection of primary magnesian chloride brines, which inflow into underlying Paleozoic and Proterozoic
rocks from Permian evaporite paleobasins, plays the principal role in the formation of chlorocalcium brines that are predominant
in the sedimentary cover of the Volga-Urals sedimentation basin. The problem of metamorpbization of brines by exchange-adsorption
and hydrolytic processes in terrigenous rocks and the problem of metasomatic dolomitization of limestones are discussed. 相似文献
9.
Lithology and conditions of the formation of Paleozoic rocks in northern areas of the Scythian Plate
The Paleozoic sequence recovered during the prospecting for oil and gas in different areas of the Scythian Plate is composed of terrigenous rocks (sandstones, siltstones, silty pelites, mudstones, shales, and phyllites) of different stages of alteration varying from late catagenesis to initial metamorphism. Their investigation allowed us to refine the sedimentation environment during different Carboniferous and Permian epochs at the southern margin of the East European Craton. 相似文献
10.
11.
《International Geology Review》2012,54(11):1279-1297
The Paleozoic tectonic evolution of Hsieh-fen-shan, western Hunan, belongs to the Caledonian and Hercynian tectonic cycles. The base of the lower Paleozoic group is defined by a geographical unconformity; the Sinian system unconformably overlies the Pan-ch'i group of the Proterozoic. The Hsieh-fen movement represented by this unconformity had not transformed this area into a platform. The lower Paleozoic group may be divided into four structural stages: Lower Sinian, Upper Sinian-Cambrian, Lower Ordovician and Middle Ordovician-Silurian. These stages are represented by the corresponding sedimentary formations: lower terrigenous elastic formation, siliceous and carbonate rocks intercalated with shale, flush formation and upper terrigenous elastic. Due to the absence of magmatic activity it is believed to be of the miogeosyncline type. In the Variscan cycle this area was already consolidated and partly covered with upper Paleozoic neoplatform sediments. Hereditary characters of the early Paleozoic tectonic evolution are obvious. According to the isopachous maps there occurred a strong tectonic differentiation at the end of the Cambrian. In Early Ordovician a northeast extended flysch geosyncline formed, and to the west of it, an uplifted denudation region. The eastern part of the uplifted region rose strongly, in parallel with the flysch geosyncline and with similar dimensions, and may be considered a geanticline. The geosyncline and geanticline have asymmetrical forms, their neighboring flanks being steeper than their opposite ones. Consequently the existence of a so-called pre-Sinian Hsieh-fen axis has not been proved and the boundaries of the Southwestern Platform with the adjoining southeastern Caledonian fold may be located approximately along T'ao-yuan, Yuan-ling Chen-chi, Hsin-Hua and Ch'ien-yang. – Authors. 相似文献
12.
泥盆纪是秦岭构造与古地理格局发生重大变革的时期。秦岭的泥盆系主要分布在南秦岭。资料表明，南秦岭泥盆系不是在统一的盆地中形成的，而是被古陆分隔的几个裂陷盆地的沉积产物。柞水石瓮子地处镇安盆地北缘，该处滑塌块体和斜坡砾岩广泛发育，物源为沿山阳－凤镇断裂向南作大规模逆冲推覆而被掩盖消失的小磨岭古陆，其形成受早古生代南秦岭区域抬升、全球海平面下降以及区内山阳－凤镇断裂和镇安－板岩镇断裂强烈活动的控制。区域性同造山陆块隆升与全球海平面下降造成了南秦岭晚古生代与早古生代地层之间区域性的不整合，一南秦岭在继续向北俯冲的同时，又沿南缘的勉略－巴山断裂带发生扩张，其内部也因拉张作用形成裂陷与块断隆起相间的古地理格局。南秦岭区域性隆起和裂陷可能与加里东运动和勉略有限洋盆的打开相关联。 相似文献
13.
A. I. Malinovsky V. V. Golozubov V. P. Simanenko 《Lithology and Mineral Resources》2005,40(5):429-447
Based on structure, mineralogy, petrography, and geodynamic setting of sedimentation, Barremian(?)-Albian terrigenous rocks in the Kema terrane (Eastern Sikhote Alin) are interpreted as back-arc rocks of the Moneron-Samarga island-arc system. The composition of terrigenous rocks indicates that an ensialic volcanic island arc, the basement of which was composed of the oceanward-advancing continental crust fragment, served as the main source of clastic material. Genetic features of rocks suggest their formation in the lower zone and near the foothill of submarine slope, as well as in adjacent areas of the basin plain. Accumulation of the thick gravitational sequence in the rear zone of the island arc was accompanied by active volcanic processes. 相似文献
14.
《International Geology Review》2012,54(11):28-36
Within the mountainous Taymry the oldest formations are highly metamorphosed sedimentary and extrusive rocks of Proterozoic age, overlain by less altered rocks of the Sinian complex. These in turn are overlain with angular unconformity by Lower Cambrian deposits, whose age has been determined on the basis of fossils. Paleozoic rocks are widespread, and all systems of the era are represented. Proterozoic rocks occur on the northern coast of the peninsula. The younger Sinian and Paleozoic formations are south and southeast of these. Mesozoic rocks constitute small areas in depressions. Quaternary sediments, consolidated by permafrost, are widely distributed throughout the area. Magmatic activity is well developed. The lower Proterozoic magmatic cycles began with intrusion and extrusion of basic rocks, and ended with granitoid injections accompanied by formation of pegmatitic zones. In the upper Proterozoic, magmatic activity is again characterized in early stages by extrusion and intrusion of basic rocks, and later by the formation of granitic intrusions and their facies, as well as by extrusion of felsite porphyry towards the end of the era. Intrusions of granitoids appeared in the middle Paleozoic. The upper Paleozoic was marked by the formation of traprock and sulfide mineralization. In the early Mesozoic, the occurrence of small subalkaline intrusions resulted in the formation of ores of various types. 相似文献
15.
The paper presents data on high-grade silicate–carbonate rocks (calciphyres) from the Irkut block (Sharyzhalgai uplift, southwestern Siberian craton). Their origin and age were determined from the rock characteristics, U–Pb dating, REE content, and Hf isotope composition of zircon. The calciphyres occur both as independent section fragments and as interbeds within Paleoproterozoic garnet-bearing and high-alumina (cordierite- and sillimanite-bearing) gneisses. They were produced by metamorphism of terrigenous-carbonate sediments. The terrigenous sediments range in maturity from arenites and wackes to argillaceous rocks; this is consistent with the reconstruction of the sedimentary protoliths of paragneisses, which are predominant in the metasedimentary rocks. The petrogeochemical features of the calciphyres, their LREE enrichment relative to “pure” carbonate rocks, and a distinct Eu anomaly were inherited from the terrigenous component of calc-silicate sediments. The Nd model age (2.4–2.7 Ga) of the calciphyres and the value THf(DM-2st) = 2.5–3.0 Ga for zircon from these rocks indicate that carbonate accumulation was accompanied by the supply of terrigenous material, which formed during the erosion of Archean and Paleoproterozoic crust. Zircon from the calciphyres is similar to metamorphic zircon in REE patterns and Th/U ratios. It might have been of detrital origin and then recrystallized during high-temperature metamorphism. Terrigenous-silicate rocks were metamorphosed at ca. 1.87 Ga. This is close to the previous age estimates for the terrigenous rocks metamorphism (1.85–1.86 Ga) and the age of baddeleyite from apocarbonate metasomatic rocks (1.86 Ga). 相似文献
16.
青岛青山湾—垭口出露一套浅变质的海相陆缘碎屑沉积岩,上覆岩浆锆石的LA-ICP-MS U-Pb年龄为(118.9±3.3)Ma,成熟度较低,与中新生代造山带砂岩类似。稀土元素球粒陨石化标准配分曲线均为轻稀土明显富集的右倾型,表明,研究区碎屑岩具有相同的物源区和构造背景,与活动陆缘的稀土元素配分曲线非常接近。Ce具弱的负异常,指示碎屑岩为大陆边缘海相成因,(La/Ce)N(PAAS)表明陆缘碎屑物质对该区碎屑岩有明显的贡献。主微量元素构造环境判别图解表明,研究区碎屑岩具有活动陆缘和大陆岛弧的特征,经历了相对简单的沉积演化过程;结合稀土元素配分曲线的特征,该区碎屑岩更可能是活动大陆边缘沉积形成。主微量元素分析揭示研究区碎屑岩物源富长英质岩石,镁铁质岩石作为物源也参与到成岩过程中。 相似文献
17.
I. M. Simanovich 《Lithology and Mineral Resources》2007,42(1):75-83
The simplest intergranular cleavage and foliation of clayey rocks are typical of postsedimentary lithogenesis of folded terrigenous complexes at passive continental margins if the rocks do not contain metamorphic minerals. Cleavage zones coincide with metagenesis (anchimetamorphism) zones. Cleavage is often superimposed on the rock fabric formed in the process of subsidence lithogenesis (e.g., in the Verkhoyansk terrigenous complex). In other cases, cleavage in terrigenous rocks is regarded as the final stage of the development of their microfabric formation related to folding (e.g., Jurassic sequence of southern Dagestan). 相似文献
18.
《Geodinamica Acta》2000,13(6):345-366
In the Radicondoli–Travale area of the Larderello geothermal field (Italy) new structural and petrologic data on some metamorphic units, cored from geothermal wells, reveal the existence of a wide complex of hornfels rocks. The development of the complex is related to the emplacement of Neogene magmatic rocks at a shallow depth within a Permo–Triassic terrigenous metasedimentary sequence of a low metamorphic grade. The sequence was subjected to alpine tectonic-metamorphic events. This reconstruction gives new insights in the tectonic setting of metamorphic units below the Tuscan Nappe, in southern Tuscany. Particularly, the medium and high grade metamorphic rocks seem strictly related to the development of Neogene thermal aureoles and do not represent remnants of a Paleozoic basement. Furthermore, in this sector of the Larderello geothermal system, the presence of deep geothermal reservoir at a depth of 3 000 m is mainly linked to the enhanced permeability caused by fracturing in these hornfels rocks. This fracturing is a consequence of the dehydration reaction occurring in the metapelites due to Neogene thermal metamorphism. This mechanism allowed the development of a long-lived hydrothermal system, shown by the secondary mineralogical assemblages. These testify the presence of at least two hydrothermal stages which are well preserved in the less permeable units. 相似文献
19.
本文主要研究扬子地台西部黄陵背斜周缘早古生代有机壳化石的特征、光学特性和有机质成熟度规律，同时较为详细地研究了有机壳化石反射率随热成熟度变化特点与镜质组反射率之间的关系。提出该区以有机壳化石反射率为主要指标的有机质成熟度划分方案。认为笔石、几丁虫和虫牙等有机壳化石在形态、结构和构造上具有各自的特征，并具有突起、反射色、显微结构构造、非均性、异向光性、反射率和双反射现象等光学特征。有机壳化石反射率与 相似文献
20.
The deformation value in the Lower and Middle Jurassic terrigenous rocks from the valley of the Belaya River (the northern slope of the Greater Caucasus) is quantified by the morpholology of the cleavage zones. The numeral determination of the axis ratios of the deformation ellipses by the Fry method is performed as well. It is shown that for a statistical sample of the random cross-sections of the thin sections in the terrigenous rocks with cleavage structure the deformation value can be estimated correctly. The method of random cross-sections described in this work can be used for the quantitative estimation of deformation in nonoriented samples of terrigenous rocks. 相似文献