Environmental and depositional characteristics of diatomite deposit, Alayunt Neogene Basin (Kutahya), West Anatolia, Turkey

This paper describes the geological-depositional and environmental characteristics of diatomite. The diatomite deposit is situated in the southern part of the Alayunt (Kutahya) Basin. Samples of 18 diatomites and 12 host rocks were collected from four sedimentary profiles in the spring season. Basement rocks are Paleozoic-aged metamorphic rocks (schist, phyllite, quartzite, etc.) and Mesozoic-aged ophiolitic and complex rocks. Host rocks are rhyodacitic–rhyolitic tuffite, volcanic glass. Diatomite is composed of Upper Miocene–Upper Pliocene-aged diatom species. Diatomite shows layer morphology and lies on volcanic glass layer. XRD characteristic peaks of diatomite show that it comprises dominantly of Opal-A silica, whereas volcanic glass has Opal-CT constituent. SEM and NPM photomicrographs indicate that diatomites are dominantly composed of benthic freshwater diatom species, such as Pinnularia microstauron, Pinnularia lundii, Pinnularia subrostrata, Pinnularia brevicostata, Pinnularia tenuis, Pinnularia sp., Navicula eligensis, Fragilaria construens, Mastogloia braunii Grunow, Melosira varians Agardh, Surirella capronii Brébisson, Cymbella lanceoloata, Amphora venata, Gomphonema germainii, Gomphonema angustatum and Rhapalodia gibba. These species are general indicators of shallow paleolake environment and cool climate conditions. Due to the fluvial currents and climatic conditions; lake water levels, temperature and nutrient content fluctuated through the time. Chemical data obtained from 18 diatomite samples show that while silica is the bodybuilding material for diatomite (over 89 % SiO₂), Al, Mg and Fe contents of diatomite samples might be derived from clastic materials. The concentration of Al, Mg and Fe decreases toward the lake center. Diatom genera, sedimentary profile sections and mineralogic data suggest that diatomite deposited in lacustrine-type freshwater shallow lake is associated with Upper Miocene-aged extension tectonics. Physical and filtration tests along with environmental characteristics of diatomite suggest that calcined diatomite can be used for waste treatment processes in the filter aid industry.     

金红石矿床的类型、分布及其主要地质特征

金红石及其同质多象(锐钛矿)是钛的氧化物中最具经济意义的矿产资源,也是中国当前短缺和重要的急需矿种之一。金红石矿床产出的大地构造背景主要是古老地盾区及其边缘或褶皱带中的变质地体。全球范围内,主要的金红石矿床可分为4个大类,即:变质的、与侵入岩有关的、沉积的和风化的,它们又可以分为12个类型,其中,第四纪海滨沉积砂矿是最重要的类型,榴辉岩型、碱性岩风化型和河流沉积砂矿型次之;碱性辉石岩中的钙钛矿、角闪岩型和斑岩铜(钼)矿伴生的金红石矿床经济潜力很大。大多数金红石富矿床来自榴辉岩型、与侵入岩有关的热液交代型和深度风化的碱性岩型,但在变质(粉)砂岩型和古沉积砂矿型中也有富矿床产出。     

夕卡岩型矿床成因类型及成矿特征

夕卡岩型矿床是一种具有重要工业意义的矿床类型,多年以来一直是矿床学研究工作的热点,经过一个多世纪的发展历程,对该类矿床的认识也由传统的接触交代成因演变为多种成因;但目前仍然有很多地质工作者局限于传统的接触交代成因。为了能够更好的认识该类矿床,本文在前期夕卡岩成因类型总结的基础上,归纳了各种夕卡岩及夕卡岩型矿床的主要特征及成矿作用,分析了不同成因夕卡岩类型之间的区别和联系。     

非洲锰矿床成因类型、地质特征及表生富集作用

[研究目的]非洲锰矿资源丰富,储量3.1亿t、资源量6.6亿t排名在世界上均列第一,加强非洲锰矿床的研究和认识对推动锰矿找矿工作具有重要的指导意义.[研究方法]通过对重要成矿带典型矿床的解剖总结了非洲锰矿床的成因类型、地质特征.[研究结果]非洲锰矿成因类型主要有前寒武系条带状铁建造(BIF)型、海相沉积型、陆相(三角洲...     

Palynostratigraphy and vegetation characteristics of Neogene continental deposits interbedded with the Cappadocia ignimbrites (Central Anatolia, Turkey)

A palynological analysis of the Late Miocene and Early Pliocene successions of the Cappadocian Volcanic Province (Central Anatolia, Turkey) has been carried out with the aim of reconstructing the palaeovegetation and palaeoclimatic conditions. The samples are collected from outcrop sections from three different localities (A: Akda?, B: Bayramhac?l? and G: Güzelöz). The pollen spectra reveals the existence of a steppe vegetation dominated by Amaranthaceae–Chenopodiaceae and Artemisia, typical of present day arid and semi-arid continental areas (i.e. Middle East), and Asteraceae Asteroideae in the A section (Late Miocene) developed in arid climatic conditions. The flora of the G (Early Pliocene) and lower part of the B (Late Miocene) sections reflects steppes on which Asteraceae Asteroideae was dominant. This flora also indicates arid conditions. The development of trees in the upper part of the B section was possibly related to local paleoenvironmental conditions rather than a climatic change. This study provides the first palynological data to reveal the presence of an Amaranthaceae–Chenopodiaceae and Artemisia steppe already during the Late Miocene in Turkey.     

吉林龙岗龙泉龙湾火山火口基浪堆积物粒度特征及搬运机制分析

龙泉龙湾是射汽岩浆爆发形成的复合式低平火山口湖。龙泉龙湾火山近火口基浪堆积物地层特征为含有火山弹的厚层粗粒-细粒火山砂与薄层细粒火山砂的韵律层,发育气管构造、透镜体构造、下陷构造、U型下蚀堆积构造和丘状构造等。碎屑粒度中值Mdφ为-2．8～1．8,分选系数σφ为1．38～3．23,整体粒径大、分选差。碎屑成分主要是浮岩碎屑、基岩碎屑和晶屑。本文在火山地层堆积构造和粒度特征研究基础上,通过应用SFT分布模式分析发现,龙泉龙湾火山近火口火山碎屑动力学模式主要以牵引为主,其次为弹道和跳跃,悬浮相对较少。     

Stable isotope study of antimony deposits in the Muratdagi region,western Turkey

The Muratdagi region is rich in antimony deposits having the following common characteristics: post Miocene age, location on the down-thrown blocks next to normal faults, in the vicinity of active or fossil thermal springs, and in contact with carbonate rocks. The isotopic composition of — 7. SMOW of the mineralizing fluid calculated from the measured ° ¹⁸O of quartz and the fluid inclusion microthermometry, is indicative of meteoric water origin. The ° ¹³C of the inclusion CO₂ of — 19.1 to — 25.4 PDB is indicative of interaction with organic material-graphite. The ° ³⁴S of stibnite — 3.6 to — 0.7 is, in view of the mineral assemblage, indicative of magmatic origin of the sulphur. A tightly confined set of structural, lithological, hydrological and geochemical features define a sequence of geochemical processes; formation of acid and reducing fluid, leaching and transport of antimony complexes and precipitation of stibnite within defined lithological units. The set of processes seems to have taken place within a space of 5000 m lateral and 1000 m vertical extension.     

The Upper Pleistocene deposits at Cassington,near Oxford,England

For much of the Middle and all of the Upper Pleistocene the Upper Thames valley has remained outside the limit of ice advance. The main agents of landform evolution have been the River Thames and its tributaries, which have cut down episodically and in so doing have abandoned a series of river terraces. This study reports the findings of an investigation into exposures in the deposits underlying the Floodplain Terrace at Cassington, near Oxford, England. The sequence exposed reveals a stratigraphy of basal, predominantly fine-grained, lithofacies overlain by coarser gravel lithofacies. The fluvial architecture of these deposits indicates a major change in fluvial style from a low-energy (meandering) to a high energy (braided) channel system. The flora and fauna from the lower fine-grained lithofacies display a marked change from temperate at the base, to colder conditions towards the top, indicating a close association between deteriorating climate and changing fluvial depositional style. Amino acid and luminescence geochronology from the basal fine-grained lithofacies suggest correlation with Oxygen Isotope Stage 5 and hence it is argued that the major environmental change recorded at the site relates to the Oxygen Isotope Stage 5–4 transition. Deposition of much of the overlying gravel sequence probably occurred during Oxygen Isotope Stage 4, suggesting that the latter half of the Devensian may be less significant, in terms of fluvial landscape evolution in the Upper Thames valley, than was believed previously. © 1998 John Wiley & Sons, Ltd.     

Depositional setting and geometric structure of the Beypazari lignite deposits, Central Anatolia, Turkey

The Neogene Beypazari basin is one of the important coal districts of Central Anatolia with approximately 600 million short tons lignite reserves. The coal-bearing Neogene sediments occurring in the Beypazari basin are divided into seven formations, in ascending order; Çoraklar, Hirka, Akpinar, Çayirhan, Bozbelen and Kirmir Formations with Sariyar Limestone and Teke volcanics.The Çoraklar Formation consists of cross-bedded sandstones, channel-fill conglomerates, mudstones, carbonaceous shales and volcanoclastic pebblestones, which are fluvial in origin. The lower lignite seam occurs in the lower part of the Çoraklar Formation.The upper lignite seam occurs in the uppermost part of the Çoraklar Formation and is overlain by the Hirka Formation with a sharp contact. The Hirka Formation consists mainly of alternating shale, mudstone, bituminous shale, claystone, tuffite and silicified limestone, and they all are apparently of lacustrine origin.The lignite deposite occur in the Çayirhan and Koyunaǧili parts of the Beypazari Neogene basin. The Çayirhan coal field consists of lower and upper lignite seams, but the Koyunaǧili field contains only an upper lignite seam.The lower lignite seam, which does not crop out at the surface, indicates a fluvial origin of the lignite deposits, based on the lateral discontinuity and the lower sulphur content of the lower lignite seam, and the sedimentologic and stratigraphic features of the associated sediments. But the uniform stratigraphic and sedimentologic features, high sulphur content and wide-spread distribution of the upper lignite seam indicate that the upper lignites were deposited probably in a mud-flat facies of playa-lake environment. The lower and upper lignites are completely different in relation to the depositional environment, the geometry and degree of rank in lateral directions.The lateral spreading and geometry of the lower lignite deposits were controlled by channel, floodplain and well-drained marshes of a fluvial system. On the basis of recent drillings and field investigations, the lower lignite deposit has been demonstrated to be a linear spreading parallel to the axis of the channel fills and throughcross beds in clastic sediments of fluvial facies. Therefore, the lower lignite deposits trend along a northeastern direction and is not expected to be as widely spread as the upper lignites.     

Some last glaciation drift deposits near Pontypridd,South Wales

Drift deposits exposed in a large open cut are described. The basal member of the sequence consists of bedded sandy gravels, and these are overlain by a grey silty sand containing abundant striated pebbles and boulders. The uppermost deposit consists of a brown poorly sorted drift containing silty and sandy lenses. Analysis of the texture, index properties and densities of the sediments, together with the shape, lithology and fabric of the contained pebbles suggests that the basal gravels were deposited by subglacial meltwater, the grey drift is a lodgement till, and the uppermost brown rubbly drift was formed by solifluction of the till, with the addition of frost shattered sandstone from the hilltop above. It is suggested that the glacigenic sediments are of Devensian age, and the solifluction layer Late Devensian.     

Landscape planning and management strategies for the Zir Valley,near Ankara,Turkey

This paper proposes a landscape planning and management method for river basins within the context of the European Landscape Convention (ELC) and European Water Framework Directive (WFD). This method has been applied to the Zir Valley in Ankara, Turkey. Landscape planning is identified by the ELC (European Treaty Series No. 176, 2000) as an important, forward-looking action to enhance, restore or create landscapes. The ELC also states that landscape management should promote sustainable development to ensure the non-degradation of landscapes and to help harmonize inevitable changes. The WFD (Directive 2000/60/EC of the European Parliament and of the Council, 2000) is a set of guidelines for managing large bodies of water. Its principle directive is to identify water bodies and the adjacent land areas that influence, and are influenced by, those water bodies. These are called River Basin Districts, and act as essential physiographic landscape units. While several regulations related to environmental planning, and used on a national as well as European basis, tend to utilize the same tools in practice, there are dissimilarities in how they are specifically applied and little effort is being made to promote a cooperative approach. In this paper, a National Approach for River Basin Management is proposed. This approach, which includes a landscape planning and management method based on landscape form and function, was developed to address the common purposes of the ELC and WFD.     

Geochemical characteristics of iron ore deposits in central eastern Turkey: an approach to their genesis

ABSTRACT

Economically the most important iron deposits of Turkey occur as: (1) skarn-hosted (SH)-type ore deposits, occurring along the contacts between syenitic-monzonitic intrusives and limestone or serpentine; (2) vein-type deposits, found between the serpentine and limestone (SLH); or (3) ore deposits that are entirely within the limestone (LH).

Elemental associations are defined as: Fe+Ni+Cr+U+Bi+Rb+Mg+Ga for the SH-type ores; Fe+Cr+Mn+Nb+V for the SLH-type ores; and Fe+Ag+Au+Cr+Ba+As+Pb+Sb+Ni for the LH-type ores. Positive correlations between Fe, U, Bi, and Rb for the SH type indicate that late magmatic hydrothermal input was related to monzonitic intrusions. Chondrite-normalized rare earth element (REE) patterns of the 14 deposits show very weak light/heavy REE (LREE/HREE) fractionation. Similarities of REE patterns, particularly between the SH and LH types, may indicate a common source of REEs and Fe. Ce depletion in the LH ores indicates long-term fluid flow and interaction with marine sediments. Ni, Cr, and V enrichment of all deposits indicates that iron was scavenged from the serpentinized ultra-basic-basic rocks and transported along fracture zones by hydrothermal solutions driven by intrusions. The iron deposits were formed around the magmatic bodies, or tectonic contacts between the serpentine and the limestone.     

超大型金刚石矿床、磷矿床、油气田、油页岩矿床与碳质球粒陨石星子的成因联系

通过对太阳系起源的研究,笔者指出,超大型金刚石矿床、磷矿床、油气田和油页岩矿床,都与碳质球粒陨石星子有成因联系。碳质球粒陨石星子被吸积于原始地球上地幔表层,形成原始富碳区。当地壳形成后,富碳区的岩石圈没有被软流层的对流作用均匀化,并在155—250km深度范围内,碳质聚合成金刚石。随着金伯利岩和钾镁煌斑岩岩浆侵位,金刚石被带入地壳上部形成金刚石矿床。在富碳区,除金刚石矿床外,还形成了超基性岩-碱性岩-碳酸岩富磷杂岩体及超大型,大型磷灰石矿床。富磷杂岩体为超人型磷块岩矿床的形成提供了成矿物质,也为成油生物群的繁殖提供了矿物养料,从而为形成超大型油气、油页岩矿床创造了物质条件。碳质球粒陨石中的有机质在高温条件下合成油气,被封存于大陆岩石圈上地幔部分,在构造条件有利时进入储油构造,促进了超大型油气田的形成。超大型矿床的存在,是岩石圈成矿物质横向不均匀性的反映。     

Early Miocene lacustrine deposits and sequence stratigraphy of the Ermenek Basin,Central Taurides,Turkey

The lacustrine Ermenek Basin evolved as a SE-trending intramontane graben affected by strike–slip deformation, with the initial two lakes merging into one and receiving sediment mainly through fan deltas sourced from the basin's southern margin. The northern margin was a high-relief rocky coast with a wave-dominated shoreline. The Early Miocene lacustrine sedimentation was terminated by a late Burdigalian marine invasion that drowned the basin and its surroundings. The lacustrine basin-fill succession is up to 300 m thick and best exposed along the southern margin, where it consists of four sequences bounded by surfaces of forced regression. The offshore architecture of each sequence shows a thin lowstand tract of shoreface sandstones overlain by a thick transgressive systems tract of mudstones interbedded with sandy tempestites and delta-derived turbidites, which form a set of coarsening-upward parasequences representing minor normal regressions. The corresponding nearshore sequence architecture includes a thick lowstand tract of alluvial-fan deposits overlain by either a well-developed transgressive systems tract (backstepping parasequence set or single fan-deltaic parasequence) and poorly preserved highstand tract; or a thin transgressive tract (commonly limited to flooding surface) and a well-developed highstand tract (thick fan-deltaic parasequence). The sequences are poorly recognizable along the northern margin, where steep shoreline trajectory rendered the nearshore system little responsive to lake-level changes. The resolution of local stratigraphic record thus depends strongly upon coastal morphology and the character of the depositional systems involved.The sequential organization of the basin-fill succession reflects syndepositional tectonics and climate fluctuations, whereas the lateral variation in sequence architecture is due to the localized sediment supply (deltaic vs. nondeltaic shoreline), varied coastal topography and differential subsidence. The study points to important differences in the sequence stratigraphy of lacustrine and marine basins, related to the controlling factors. A crucial role in lacustrine basin is played by climate, which controls both the lake water volume and the catchment sediment yield. Consequently, the effects of tectonics and the dynamics of changes in accommodation and sediment supply in a lacustrine basin are different than in marine basins.     

Geological, mineralogical and geochemical characteristics of zeolite deposits associated with borates in the Bigadiç, Emet and Kirka Neogene lacustrine basins, western Turkey

The Bigadiç, Emet and Kirka lacustrine basins of western Turkey may be considered as Tibet-type graben structures that were developed during the Miocene within the Izmir-Ankara suture zone complex. The volcanic-sedimentary successions of these basins are made up of mudstone, carbonate (limestone and dolomite) and detrital rocks, and also of crystal or vitric tuffs about 135 to 200 m thick. The Degirmenli (Bigadiç), Emirler (Bigadiç) Köpenez (Emet) and Karaören (Kirka) tuffs constituting the zeolite deposits are situated beneath four borate deposits (colemanite, ulexite, borax). The most abundant diagenetic silicate minerals are K- and Ca-clinoptilolites in the zeolite deposits, and Li-rich trioctahedral smectites (stevensite, saponite and hectorite) and K-feldspar in the borate deposits. In the Degirmenli, Emirler. Köpenez and Karaören deposits, the following diagenetic faciès were developed from rhyolitic glasses rich in K and poor in Na: (glass + smectite), (K-clinoptilolite + opal-CT), (Caclinoptilolite + K-feldspar ± analcime ± quartz) and (K-feldspar+analcime+quartz). K-feldspar which is also rarely associated with phillipsite (Karaören) and heulandite (Degirmenli and Karaören), succeeds clinoptilolite and precedes analcime in these diagenetic facies where dioctahedral smectites, opal-CT and quartz are the latest minerals. No diagenetic transformations exist between clinoptilolite, K-feldspar and analcime that were formed directly from glass. The lateral facies distributions resulted from the differences in salinity and pH of pore water trapped during deposition of the tuffs, but vertical distributions in vitric tuffs seem to have been controlled by the glass/liquid ratio of the reacting system and the permeability or diffusion rate of alkali elements. The Bigadiç, Emet and Kirka zeolite deposits which were formed in saline basins rich in Ca and Mg ions, show similar chemical changes, i.e. loss of alkalis and gain in alkaline-earth elements that have taken place during the diagenetic transformation of rhyolitic glasses to dioctahedral smectites or clinoptilolite. The absence of sodic zeolites such as mordenite, erionite, chabazite and silica-rich phillipsite is mainly due to the very high K/Na ratio of the starting materials rather than initial alkaline conditions or high Na content in lake waters.     

Genetic classification of uranium deposits

Commercial uranium deposits and those likely to become commercial in the near future are genetically classified as magmatic, hydrothermal, exogenous, metasedimentary, and deposits of questionable origin. A brief discussion of each type is included. — C.E. Sears.     

Sulfur isotope study of source and deposits of stibnite in the Turhal Area,Turkey

The Turhal antimony sulfide ore deposits are hosted by a Permian-Jurassic sequence which consists of black phyllites at the base followed by interbedded phyllites and calcareous quartzites with metabasite interlayers and then by brown-gray phyllites with marble blocks. Four different styles and three distinct episodes of mineralization were distinguished according to deposition features of the ores and kinkbands in the stibnite crystals. Stibnite from stratiform, disseminated and vein occurrences as well as pyrite from black phyllites showed the following sulfur isotope composition (³⁴S): +2.8 and +3.0 for stratiform stibnite (n = 2), +3.6 and +5.5 for disseminated stibnite (n = 2), +2.5 to +7.8 for vein stibnite (n = 11) and -6.1 to +0.1 for pyrite (n = 3). The ³⁴S compositions of stibnite are interpreted as suggesting an ultimately single source for sulfur in the various styles of mineralization, i.e. synsedimentary volcanic exhalations for the stratiform and disseminated together with ores and hydrothermal mobilisation of these as well as leaching of volcanic rocks to form the vein ores. Deep basinal fluids probably under normal geothermal gradient conditions caused the leaching of the primary sulfides as suggested by the oxygen isotope composition of vein quartz associated with the ores. By contrast sulfur in pyrite is essentially a derivation of seawater sulfate through bacterial and/or chemical reduction.     

图们江河口沼泽沉积物的粒度特征及碎屑源分析

经对图们江河口沼泽沉积物的粒度分析,其粒度特征:①分选差,粒径φ值为5.66~8.74(0.020 mm~0.002 mm),平均φ值为7.57(0.005 mm);②粒级构成为:粉砂74.21%,黏土25.79%;③频率曲线以双峰态为主,主要为负偏态。热释光测年结果表明该套样品沉积时间为晚更新世末期至今。根据沉积物粒度分布特征推断该区沼泽沉积物主要为图们江碎屑物由上游搬运到河口地区,堆积在河床和河漫滩上,在旱季由风搬运到沼泽中并堆积下来。雨季的面流也将少量细粒碎屑搬运到沼泽中并沉积下来。     

On the formation mode of the Guleman chromite deposits (Turkey)

Kefdag and Soridag chromite pods occur in upper mantle residual peridotites, which consist of harzburgite and dunites. The peridotites represent the residual of multistage, depleted upper-mantle peridotites. The chromitite bodies were formed during the uprising of chromium-rich picritic melts, through the residual upper mantle diapir, along the magma conduits. Chromitite grains were deposited in the caves of the magma conduits under the control of the convection currents.