Rocks of the Bazhenovo and Abalak Formations, Central Krasnoleninsk Arch, Western Siberia: Composition, Structure, and Formation Conditions

The finding of hydrocarbon accumulations in Upper Jurassic rocks of the Krasnoleninsk Arch, which were previously considered fluid trap and oil source sediments, stimulated us to have a new look at these rocks. The analysis of geophysical data on boreholes revealed that reservoirs in Upper Jurassic rocks are mainly represented by siliceous and carbonate varieties, which were named potentially productive beds. This work presents results of the detailed investigation of the lithology of Upper Jurassic rocks for distinguishing different rock types (including potentially productive beds) with the aim of their correlation and prediction of lateral distribution.     

Composition,Structure, and Conditions of Formation of Fluorine-Bearing Sodalite: Experimental Evidence

Fluoro-sodalite was synthesized for the first time at temperatures of 400–800°C and H₂O pressures of 1–2 kbar in the Si–Al–Na–H–O–F system. X-ray diffraction and infrared spectroscopic investigations showed that fluorine is incorporated in the sodalite structure as anionic octahedral groups, [AlF₆]^3–, the number of which can vary from 0 to 1. Correspondingly, the end-members of the F-sodalite series are Na₇(H₂O)₈[Si₅Al₇O₂₄] and Na₈(AlF₆)(H₂O)₄[Si₇Al₅O₂₄]. Depending on the composition of the system, F-sodalite associates at 500–650°C with nepheline, albite, cryolite, and villiaumite, which are joined by analcime below 500°C and aluminosilicate melt above 650°C. Fluorine-bearing sulfate–chlorine-sodalite was found for the first time in a pegmatite sample from the Lovozero massif. The highest fraction of the fluorine end-member in natural sodalite is 0.2. The incorporation of F into the sodalite structure requires much more energy compared with Cl^– and SO ₄ ^2- , because it is accompanied by a structural rearrangement and a transition from tetrahedral Al to octahedral Al.     

Massifs of Disintegrated Granitoids in the Junction Zone of the East European and West Arctic Platforms: Composition,Age, and Hydrocarbon Potential

Geotectonics - In the Trollfjord–Rybachy–Kanin fault zone, the major convergent suture between the East European and West Arctic platforms, on the isthmus of Cape Vestnik located...     

Formation Conditions and ore potential of black shales of the Udokan Group,East Siberia

Peculiarities of formation and ore potential of black shales of the Paleoproterozoic Udokan Group are considered. They are compared to the stratotype (Khokholma Formation, Sukhoi Log gold deposit). The black shales are confined to lower parts of the Paleoproterozoic sequence of the Udokan Group. They are observed in sections of the Chitkanda, Inyr, Ayan, and Ikab’ya formations. The black shale complex of the Udokan Group is divided into three levels of Au concentration. The first level with background Au contents is typical of barren shales; the second level is confined to sulfidized rocks; and the third level is related to sulfide-quartz veins in the black shales. The average Au content is 0.12 g/t in the sulfidized shales and 0.28 g/t in the sulfide-quartz veins. Black shales of the Udokan Group and Khokholma Formation were formed in a relatively deep shelf zone, while those of the Shaman Formation precipitated in a shallow zone. Protoliths of black shales of the Udokan Group contained graywackes, diorites, syenites, basic rocks, and tuffites. Protoliths of black shales of the Khokholma Formation were produced by the intense weathering of basic and ultrabasic rocks.     

Fluorides and Fluorcarbonates in Rocks of the Katugin Complex,Eastern Siberia: Indicators of Geochemical Mineral Formation Conditions

The paper discusses the chemical composition and parageneses of fluorides and fluorcarbonates in rocks of the Katugin Complex, with which a unique deposit of REE–Nb–Ta ore with cryolite is associated. In mineralogy and chemical composition, the rocks correspond to biotite, biotite–amphibole, arfvedsonite, and aegirine–arfvedsonite granites, which were regarded in earlier publications as granite-like metasomatic rocks. Aegirine–arfvedsonite granite contains a cryolite–gagarinite assemblage, which reflects depletion of Ca in the mineral-forming medium and enrichment in Na and F. Arfvedsonite granite is characterized by intergrowth of yttrofluorite with fluocerite and gagarinite, which indicates a relative enrichment in Ca and low CO₂ content. Biotite granite is characterized by an assemblage of fluorite with titanite, apatite, and monazite as evidence for an elevated Ca concentration along with moderate F and P contents in the system. Neighborite, coulsellite, gagarinite, fluocerite, and tveitite-(Y) appear in biotite–amphibole granite along with replacement of annite with riebeckite and development of albite after microcline. All this indicates that a moderately alkaline Na-fluoride solution with a low Ca concentration affects biotite granite.     

甘肃柳园地区花岗质岩石时代及成因

柳园花岗质岩石在空间上与榴辉岩共生,是探讨区域构造演化的关键岩石类型之一。岩石学,地球化学和锆石Ｕ－Ｐｂ同位素测年研究表明,这套花岗岩侵入时代系新元古代（８８０Ｍａ）具有先存地壳与幔源岩浆混合的特点,推断系陆陆碰撞地壳增厚的产物。     

Organic Carbon versus Major Elements Relationship in Rocks of the Bazhenov Formation,Western Siberia

A close relation of the organic carbon (C_org) content with major has been established for rocks of the Upper Jurassic–Lower Cretaceous Bazhenov Formation. Applying the method of multiple linear regression, it has been demonstrated that the C_orgcontent in rocks of the Bazhenov Formation is stringently controlled by its bulk chemical composition. This inference is consistent with the existing ideas regarding a close interrelation between the following main components of rocks: organic carbon and authigenic quartz formed on remains of Radiolaria; pyrite formed in a highly reducing medium of C_org-rich sediments; and terrigenous clayey material diluting the authigenic siliceous–carbonaceous–pyritic matrix. These components chiefly determine the spectrum of major elements in the Bazhenov Formation. The establishment of the close relation between the C_orgcontent and the group of major elements refutes the suggestion of some authors that siliceous material was supplied to nonlithified sediments of the Bazhenov sea by hydrothermal solutions, because this mechanism would have inevitably upset geochemical relations between elements in the studied rocks.     

Yurchik Massifs in Kamchatka: Age and affiliation to magmatic associations

Petrographic and isotopic-geochemical data obtained on basic and ultrabasic rocks from the Yurchik Massif in the Ganal block of crystalline rocks in Kamchatka indicate that the distribution of major and trace elements in these rocks are analogous to those in the fractionation products of high-Al tholeiites occurring in island arcs in the eastern continental margin of Eurasia. Allivalites and dunites found as nodules in gabbronorites and gabbro of the massif are thought to be early cumulates of arc basalts. Petrographic and geochemical characteristics of the Yurchik Massif make it different from Ni-bearing Paleocene-Eocene (approximately 50 Ma) norite-cortlandite intrusions in the Sredinnyi Range of Kamchatka. U-Pb zircon and ⁴⁰Ar/³⁹Ar dates for rocks from the massif definitely testify to its younger, Early Miocene (approximately 22 Ma) age.     

辽西义县组的地质时代

长期以来辽西义县组地质时代存在争论。通过对义县组命名地义县上底家沟—砖城子剖面义县组下部玄武岩的定年 ,获得K Ar年龄 131.2± 2 .6Ma ,坪年龄tp130 .4± 1.0Ma ,总气体年龄ttg130 .1± 1.3Ma ,等时年龄tI130 .5± 1.5Ma。这一结果表明 ,辽西义县组的地质时代应属早白垩世 ,其时代可与浙西劳村组、江苏宁芜盆地龙王山组、安徽庐枞盆地砖桥组对比。     

Composition and Formation Conditions of Neoproterozoic Phosphorites in the Middle Urals

Lithology and Mineral Resources - Phosphorite breccias compose a 6-m-thick member in the Vendian terrigenous Kernos Formation in the basin of the Mezhevaya Utka and Sylvitsa rivers (Middle Urals)....     

The Features of the Geological Structure and Oil Potential of the Vikulov Formation within the Vostochno-Kamennoye Field (Western Siberia)

Geological and geophysical materials were analyzed to study the peculiarities of the geological structure of the Vikulov Formation within the Vodorazdelnyi license area. The presented data makes it possible to characterize the geological structure of the studied area more informatively and make an interpretation of the seismic data. The analysis of geological information (well logging and test results) confirms the established level of the water–oil contact in the studied area of the field, making it possible to recalculate the oil reserves.     

鄂西地区大隆组沉积类型及地质时代

鄂西地区的大隆组富含菊石类化石 ,下部产 K onglingites、 Sanyangites、 Jinjiangoceras等 ,上部产 Pseu-dotirolites、 Tapashanites、 Changhsingoceras、 Pleuronodoceras等 ,时代为晚二叠世吴家坪晚期至长兴期。自西而东存在 3种沉积类型 ,即为硅质岩—灰、泥岩型、泥岩—硅质岩型和硅质灰岩—泥岩型。硅质岩层在区域上存在穿时性现象。大隆组与下伏吴家坪组的接触关系有两种 :连续沉积的整合接触和间断沉积的似整合接触     

四川石棉西部地区金矿床形成时代

四川石棉西部地区金矿床和矿点分布在扬子地块盖层碳酸盐岩和基底元古宙变质闪长岩以及中生代石英斑岩中的北北西和北北东走向断裂中。矿脉为含金黄铁矿-（黝铜矿）-多金属硫化物-石英脉、含金黄铁矿-石英脉和含金硅化糜陵岩等,围岩蚀变为硅化、白（绢）云母化、碳酸盐化、绿泥石化和黄铁矿化等。用40^Ar／39^Ar阶段加热法测定瓦斯沟、黄水沟、大岩房、金洞子和金台子5个金矿床蚀变白云母。4^Ar／39^Ar坪年龄分别为约22Ma、25～28Ma、20Ma、20Ma和32-34Ma,代表该地区主要金矿床的矿化蚀变时间。石棉西部地区金矿床是在渐新世和中新世早期的伸展构造背景下形成的。     

Pyritization of Rocks in Black Shale/Host Rock Transition Zones: Evidence from the Bazhenov Formation,Western Siberia

Lithology and Mineral Resources - A complex of lithological-geochemical studies was carried out in rocks of the Upper Jurassic–Lower Cretaceous Bazhenov Formation and their transition zones...     

First Data on the Age of Metamorphic Schists from the Taz Peninsula (Arctic,Western Siberia)

Doklady Earth Sciences - The 40Ar/39Ar dating of metamorphic schists from the basement of the West Siberian Platform exposed by Lenzitskaya well no. 77 on the Taz Peninsula was performed. The...     

Cambrian Magmatism in the Northern Urals: New Data on the Age and Formation Conditions

Cambrian igneous formations in the Northern Urals were identified and described for the first time. It was established that the Timanide orogeny terminated in the Early Cambrian and was followed by continental rifting above a mantle plume in the Late Cambrian.     

北京周口店南窖石英二长岩岩枝的锆石U-Pb年龄和地质意义

应用LA-ICP-MS技术测得北京周口店南窖南沟石英二长岩岩枝两个样品的岩浆锆石的206Pb/238U年龄分别为(133.0 +2.0/-5.0)Ma和(134.0 +1.0/-5.0)Ma,全部数据的统计权重年龄为(134.0 +1.0/-2.0)Ma.测定结果将这些石英二长岩岩枝的侵入时代限定在晚燕山期,并将发育在奥陶系与石炭系平行不整合面之间的构造滑动断层的发育年龄约束在约134 Ma之前.南窖石英二长岩岩枝是华北东部岩石圈减薄峰期的产物.     

Paleozoic evolution of the External Crystalline Massifs of the Western Alps

The External Crystalline Massifs (ECMs) of the Alps record, during the Paleozoic, the progressive closure of oceanic domains between Gondwana, Armorica and Avalonia in three contrasting tectonic domains. The eastern one shows the Early Devonian closure of the Central-European Ocean between Armorica and Gondwana along a northwest dipping subduction zone. The western domain is marked by Lower Ordovician rifting followed by Mid-Devonian obduction of the back-arc Chamrousse ophiolite. The central domain underwent Late Devonian to Dinantian extension in a back arc setting associated with southeast dipping subduction of the Saxo-Thuringian Ocean. Based on tectonostratigraphic correlations, we propose that the western domain shows an affinity to the Barrandian domain while the eastern and central domains correspond to the north-eastward extension of the Moldanubian zone, to the south of the present-day Bohemian Massif. From Mid-Carboniferous to Permian, the eastern and central domains of the ECMs, including the internal parts of the Maures Massif, Sardinia and Corsica were stretched towards the south-west along the ca. 1500 km long dextral ECMs shear zone preceding the opening of the Palaeo-Tethys ocean.     

鲁西中生代金矿形成时代、物质来源及问题讨论

本文将鲁西地区"幔源岩浆型金矿"划归为"与中生代侵入岩有关的金矿",与金成矿相关的岩浆岩主要为产于断裂带及其附近或不同断裂交汇部位的中生代燕山期中性和碱性岩浆岩。根据碳、氢、氧、硫、铅等稳定同位素组成,金矿成矿作用过程中至少部分物质来源于下地壳或上地幔,局部有围岩物质成分的带入。鲁西地区各金矿成矿年龄相差较大,测得兰陵龙宝山含矿石英脉K-Ar年龄为96.2Ma,沂源金星基性岩床年龄为141Ma,代表了与其有关的层状金多金属矿成矿年龄。根据沂南金场早期矽卡岩和晚期矽卡岩黑云母Rb-Sr年龄分别为133±6Ma和128±2Ma,推测其成矿时间为128~121Ma。在剥蚀程度较浅或隐伏岩体及其周围是找矿有利地区。层状微细浸染型金矿的找矿方向重点在岩体外围,其它类型金矿找矿方向重点是在岩体或岩体接触带附近。该区中生代侵入岩缺乏深入系统研究,成矿时代缺乏精准的测年,平邑归来庄金矿尚无可行的测年方法。     

西秦岭北缘花岗质岩浆作用及构造演化

西秦岭北部江里沟、阿夷山、德乌鲁、温泉和中川5个花岗质岩体岩石学、地球化学和LA-ICP-MS锆石U-Pb年代学研究结果表明,花岗岩体的岩性主体为花岗闪长岩-二长花岗岩,属高钾钙碱系列,少数为钙碱系列;形成时代为264~216Ma。江里沟、阿夷山和中川岩体属弱过铝质花岗岩(ACNK1.05),温泉岩体和德乌鲁岩体属准铝和弱过铝质花岗岩(ACNK=0.95~1.05);花岗岩具有埃达克岩(Sr400×10-6,Yb2×10-6)或喜马拉雅型花岗岩(Sr400×10-6,Yb2×10-6)的地球化学特征,或两者兼而有之。花岗岩浆起源于下地壳的部分熔融,源岩最有可能是古老的玄武质岩石。西秦岭北部存在埃达克岩和喜马拉雅型花岗岩,说明三叠纪时期存在陆陆碰撞或陆陆俯冲导致的地壳加厚,加厚的下地壳的部分熔融以及部分熔融发生深度的不同,形成本区具有埃达克或喜马拉雅型地球化学特点的花岗岩侵入体。埃达克岩和喜马拉雅型花岗岩对寻找金铜矿产具有一定的指导意义。