Marine Early Bajocian Deposits of the Lower Volga Region (Volgograd Region) and Their Belemnite-Based Stratigraphy

A representative early Bajocian belemnite assemblage containing four genera and 11 species (two identified in open nomenclature and five new: Eocylindroteuthis weisi sp. nov., E. mariottii sp. nov., E. yarkovi sp. nov., Homaloteuthis volgogradensis sp. nov., and Hastites orphana sp. nov.) is described from a section near the Dubovoi hamlet in the Greater Don Bend area (southern termination of the Don-Medveditsa dislocations). Some members of this assemblage were previously known from the Caucasus; however, it is possible to state the discovery of a Euroboreal belemnite fauna completely new for Russia, previously described only from Central Europe and almost unknown for Eastern Europe. The age of the studied assemblage collected from the lower part of the section, traditionally considered to be Upper Bajocian, corresponds to the Laeviuscula ammonite Chronozone and is the first reliable evidence of marine settings in the Volga Region for the early Bajocian. Two new biostratigraphic units, Beds with Eocylindroteuthis weisi and Beds with H. orphana, are introduced. The former, judging from the occurrences of its characteristic species in Western Europe, has a broad correlative potential. On the basis of datings obtained, the scheme of the formational subdivision of the Middle Jurassic of the Volga Region near Volgograd is revised, and the formerly abandoned Bakhtemir Formation is reinstated as a valid unit. Its total range is reestablished as corresponding to the upper part of the Discites (?)/Laeviuscula Chronozone (lower Bajocian)–Garantiana Chronozone (upper Bajocian).     

Paleogeographic provinces of the periglacial loess association in the middle Volga basin

Specific features of the formation and distribution of periglacial loess association in the Volga region are discussed. Based on generalization of the results of the systematic paleogeographic analysis, the paper presents a comprehensive characteristic of the polygenetic and polychronous loess rocks. The results show regional specifics in the structure and composition of loess rock horizons confined to different-aged paleogeographic zones of the Russian Plain. Provincial discrepancies in the distribution and thickness of loess rocks are demonstrated in the summary map. Comparison of the complex characteristics of the loess rocks provides insight into the general trend of spatiotemporal variability of their structure and composition. Latitudinal zonation is manifested in the thickening of loess rock sequences along the distal direction of the paleoglacial zone (on the average, from 1.3 m to 5–10 m or more) and is usually accompanied by increase in contents of the silty material and carbonates and degree of sagging. Moreover, the stratigraphic structure of sections becomes more complicated with increase of the age interval of loess–soil series. The spatiotemporal trends, which are revealed in the development and periodicity of loess formation, have a great significance for the reconstruction of paleogeographic events in the Neopleistocene.     

Spatial and Temporal Distribution of the Cryptospirifer Fauna(Middle Permian Brachiopods) in the Tethyan Realm and Its Paleogeographic Implications

The middle Permian Cryptospirifer fauna （brachiopod） has hitherto been found in more than 30 localities in the Yangtze Platform, South China. Examination of data from various localities shows that it occurs stratigraphically in three intervals in the range from the upper Kungurian to Wordian. In the Baoshan block in western Yunnan the fauna occurs in the basal part of the Daaozi Formation and is of possibly an early Wordian age. Outside China the Cryptospirifer fauna has been reported from central and northwest Iran and central Turkey, where the fauna may have an age around the Wordian／Capitanian boundary. Rapid global warming since the late Early Permian and possession of other suitable environmental factors such as proper substrate, clastic input and water depth enabled the Gondwana-derived Baoshan Block and related tectono-stratigraphic units in Iran and Turkey to host the Cryptospirifer fauna, a fauna evolved in the Yangtze Platform that is a type area of the Cathaysian province.     

Chemical Compositions of Calcites in Carbonatites from Panxi Region Implications for Genesis of Carbonatites and Associated REE Deposits

The Panxi region is important REE mineralization belt in China. Chemical compositions of calcites in carbon-atites from Daluxiang and Maoniuping REE deposits are analyzed by LA-ICPMS. At Maoniuping the reserve of REE2O3 is estimated to be more than 1.45 million tons.     

Palaeomagnetic Study on a 1765 Ma Dyke Swarm from Singhbhum Craton: Implications to the Paleogeographic Position of India

正The paleogeographic position of India within the Columbia supercontinent during Paleoproterozoic era is still uncertain because of very few reliable,high-quality palaeomagnetic data with precise geochronology.Here we     

扬子地块泥盆纪—石炭纪古地磁新结果及其古地地理意义

本文通过对扬子地块西南缘贵州独山－平塘地区泥盆－石炭纪316块定向岩心样品的系统退磁处理，揭示出晚侏罗世、新生代两期重磁化成.73个岩心样品，分布在早一中泥盆世（17个）、晚泥盆世（25个）、早石炭世（24个）和中－晚石炭世（7个）4个统计单元，得到了最可能的原生剩磁。结合已有的古地磁数据，修订了扬子地块极移曲,纯利 移曲线拟合的结果表明，扬子地块在早古生代是冈瓦那大陆的组成部分，与印度－喜马拉雅－澳大利亚地区临近。晚泥盆世、冈瓦那大陆发生大规模顺时针旋转，扬子地块开始与之分离。     

东昆仑加鲁河中三叠世含石榴石二云母花岗岩的成因及地质意义

东昆仑造山带广泛发育晚古生代-早中生代富含暗色微粒包体的花岗闪长岩类,被认为是研究壳幔岩浆混合作用的天然实验室,然而同时代的过铝质-强过铝质型花岗岩在该地区鲜有报道.在东昆仑东段加鲁河地区新识别出一套含石榴石二云母花岗岩,为了探究其成因归属及地质意义,我们对其开展了详细的矿物学、岩石学、锆石U-Pb年代学、岩石地球化学及锆石Lu-Hf同位素研究.该套岩石呈多条近平行脉状侵入花岗闪长岩中,主要组成矿物包括石英、斜长石、钾长石、黑云母和白云母,副矿物中可见少量石榴石.LA-ICP-MS锆石U-Pb定年获得含石榴石二云母花岗岩成岩年龄为242.0±1.4 Ma,属于中三叠世岩浆活动产物.化学成分上,该岩石具有高SiO₂（74.49%~75.24%）、高K₂O（4.21%~4.33%）、低P₂O₅（0.02%~0.03%）含量和过铝质-强过铝质（A/CNK值为1.08~1.12）特征,表现出较高的分异程度.其U、Th、Pb、Rb等元素相对富集,Nb、Ta、P、Ti等元素相对亏损,其中P、Ti强烈亏损,这可能与磷灰石及钛磁铁矿的早期结晶分异有关.稀土元素总量较低为（61.55×10-6~119.05×10-6）,有弱负Eu异常（δEu=0.51~0.65）.锆石ε_Hf（t）值变化范围为-8.19~-2.78（均值为-5.61）,二阶段模式年龄（T_DM2）为1.3~1.6 Ga,全岩Nb/Ta比值8.22~9.67（接近地壳比值10.91）,这与区域内近同期的黑云母二长花岗岩特征相似,均指示该岩石可能源于下地壳的重熔.岩石中广泛发育的富云包体暗示岩浆上升途中捕获围岩物质,岩浆存在明显同化混染作用.综上,本文认为东昆仑加鲁河地区的含石榴石二云母花岗岩脉为一套过铝质-强过铝质的高分异I型花岗岩,是下地壳部分熔融产生的长英质岩浆经历长期结晶分异作用并在上升途中受到围岩同化混染作用之后的产物.      

Lithological and Hydrogeochemical Implications of Ion Exchange in Sedimentary Basins: Evidence from the Volga–Ural Basin

Implications of ion exchange processes for the formation of lithological and hydrogeochemical systems under various thermobaric conditions of the subsurface hydrosphere are discussed on the basis of on-location, experimental, and thermodynamic studies. It is shown for the case of the Volga–Ural sedimentary basin that ion exchange interaction in the water–rock system bears a zonal character and is differentiated with depth. Exchange and adsorption processes are most efficient in the upper 500-m-thick supergene zone composed of terrigenous clayey rocks, where the HCO₃–Na- and SO₄–Na-waters with a mineralization reaching 20 g/dm³ are formed. In cata- and metagenetic zones at a depth of more than 1000–1500 m, these processes do not strongly affect the brine composition. Metasomatic dolomitization of limestones as an exchange adsorption process plays the crucial role in the formation of Cl–Ca-brines at that depth.     

十足目节肢动物化石在关岭生物群的发现

云南罗平岔江新江底村发现的十足目节肢动物化石产出于三叠统卡尼阶小凹组,是十足目化石在关岭生物群的首次发现,也是此类化石在中国上三叠统中首次报道。此发现增加了关岭生物群的多样性,为今后在中国三叠纪其他特异埋藏化石库中寻找更多的十足目节肢动物化石提供了新的线索。     

Distribution of Rare Metals and REEs in Brown Coal Deposits of the Upper and Middle Amur Region

Doklady Earth Sciences - The distribution of REEs and rare metals in the Paleocene and Lower–Middle Miocene brown coals of the Zeya–Bureya Basin is analyzed. The migration of minor...     

Detrital Tourmaline from the Riphean Terrigenous Deposits of the Middle Timan: Chemical Composition and Genesis

Geology of Ore Deposits - Data on the chemical composition and a degree of roundness of detrital tourmaline from the Chetlasskaya, Bystrinskaya, Vymskaya, and Kislorucheyskaya groups of Upper...     

Stratigraphy of the Bathonian-Callovian boundary deposits in the Prosek section (Middle Volga Region). Article 1. Ammonites and infrazonal biostratigraphy

In European Russia, the most complete succession of Boreal sediments of the terminal Bathonian and lower Callovian is exposed near the Prosek Settlement. After its revision, the infrazonal division of the upper Bathonian and lower Callovian and position of the Bathonian-Callovian boundary are difined more carefully. The Calyx Zone and bodylevskyi Biohorizon are established in the upper Bathonian. The base of the lower Callovian is defined at the first occurrence level of Macrocephalites jacquoti. Based on four successive ammonite assemblages occurring in lower part of the Elatmae Zone, the breve, frearsi, quenstedti, and elatmae biohorizons are identified. The joint occurrence of Boreal, Subboreal, and Tethyan ammonites in the section facilitate its correlation with the other sections of the Panboreal paleobiogeographic superrealm.     

Middle Proterozoic Vein-Hosted Gold Deposits in the Pontes e Lacerda Region,Southwestern Amazonian Craton,Brazil

Structural, geochemical, and isotope studies were carried out on the gold deposits of the Pontes e Lacerda region (Mato Grosso state, Brazil), where rocks of the Aguapei and Rondoniano mobile belts (southwestern Amazonian craton) occur. The orebodies are hosted in metavolcanic, gneiss-granite, quartzite, tonalite, and granite units. Tectonics involve oblique overthrusting (from northeast to southwest), which led to the formation of recumbent folds and thrusts (pathways for the mineralizing fluids), upright folds, and faults with dominant strike-slip component. These unconformities represent potential sites for mineralization. During geological mapping, it was observed that the orebodies consist of quartz, pyrite, and gold, and that the hydrothermal alteration zone contains quartz, sericite, pyrite (altered to limonite), and magnetite (altered to hematite). Chalcopyrite, galena, and sphalerite occur only in the Onca deposit. Chemical analysis of sulfides indicates high contents of Bi, Se, and Te in sulfides and gold, suggesting plutonic involvement in the origin of hydrothermal solutions.

K-Ar dating of hydrothermal sericites from gold veins yielded ages in the range from 960 to 840 Ma, which may indicate the age of original crystallization of sericite. Pb-Pb dating in galenas yielded model ages in the range from 1000 to 800 Ma for the Onca deposit, which is in agreement with K-Ar ages. Pb-isotopic ratios indicate high U/Pb and low Th/Pb for the upper-crustal Pb source before incorporation in galena crystals. The Pontes e Lacerda gold deposits yielded ages correlated to the Aguapei event and probably were formed during a Proterozoic contractional tectonic period in the southwestern part of the Amazon craton, which may characterize an important metallogenic epoch in the Pontes e Lacerda region.     

The appearance of the elements of the Protopteris floras: Paleogeographic constraints

The elements of the Protopteris floras were identified in lower Emsian deposits in areas of collision and rift-related volcanism in Gorny Altai, Tuva Trough, Khakassia, Rybinsk Depression, and the eastern Kuznetsk Basin. The appearance of this type of flora in Siberia was accompanied by short-term climatic transitions from humid to arid conditions and periodic shoreline oscillations. The eruptions of volcanoes brought chemical elements and compounds into the atmosphere, which were responsible for mutations in the plants. Natural selection, which was caused by changes in climatic conditions, also played an important role.     

Geophysical Expression of Low Sulphidation Epithermal Au-Ag Deposits and Exploration Implications –Examples from the Hokusatsu Region of SW Kyushu, Japan–

Abstract: Low sulphidation epithermal Au-Ag deposits constitute a major exploration target for many mining companies worldwide. These deposits are commonly characterized by quartz vein systems which formed at temperatures often in the range 150–250°C giving rise to major alteration halos. Accompanying mineralization and associated alteration is the destruction and redistribution of magnetite in the host rocks and the formation of various K-bearing minerals such as adularia, illite and alunite. These alteration halos can often cover an area of at least several square kilometres and as such have the potential to be detected during reconnaissance geological surveys utilizing high resolution airborne aeromagnetic and radiometric sensors.
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan.     

环渤海地区非金属矿地质特征

环渤海地区非金属矿产品种繁多、分布广泛、资源丰富、经济效益明显.区内已发现非金属矿种近80种,已探明小型以上矿产地1 294个(其中超大型矿床22个,大型矿床232个,中型矿床497个).其中菱镁矿、金刚石、滑石、硼、耐火黏土、玉石、硅灰石、石墨、硫、磷、石膏、珍珠岩、澎润土和芒硝等是本区的优势矿产,已探明小型以上矿产地436个.这些矿产主要分布在胶辽、鲁西、燕山、太行山吕梁山和内蒙古等地.单矿种区域分布极不均匀,如硼矿床、菱镁矿床集中分布于辽东地区,金刚石集中分布于鲁西和辽南地区.此外辽宁、河北、天津、山东还是我国北方海盐的主要产区.该类矿床成因有风化型、沉积岩型、变质岩型、热液型、岩浆岩型等五大类,其形成时代自太古代始,各个地质时代都有产出.     

Astronomo-climatic cycles in the sequence of Upper Cretaceous sediments of the Saratov Volga Region

The composition and genesis of the cyclic sequence of Upper Cretaceous sediments near the town of Volsk (Saratov Region) were first investigated using a series of analytical methods. The results were statistically processed using methods of manual counting, as well as spectral and wavelet analyses. Elementary formation cyclites and cyclic variations in several parameters are correlated with astronomo-climatic Milankovitch cycles.