前陆盆地钾盐矿床成因及模式——以西班牙北部埃布罗盆地为例

前陆盆地蕴藏有巨量的钾盐资源,而对于其内的钾盐矿床成因和模式还欠缺系统的总结。西班牙埃布罗盆地是由于伊比利亚和欧亚块体碰撞而形成的前陆盆地。始新世晚期(约36 Ma)海水完全从盆地退出后,在极端干旱气候作用下,由于碰撞造山导致盆地的封闭作用,在南比利牛斯前陆盆地系统的前渊带(即埃布罗盆地北部)形成了典型的厚层含钾石盐_光卤石的正常海相蒸发岩序列。后期受到构造挤压作用,钾盐地层以盐底劈的形式出露在背斜核部。埃布罗盆地钾盐成因是构造、气候和物源三者耦合作用的结果,与中国库车前陆盆地有很大的相似性。据此,作者建议可重点关注盆地南北盐丘地带苏维依组蒸发岩以及卤水的迁移方向。     

Oceanic basins in prehistory of the evolution of the Arctic Ocean

During geodynamic reconstruction of the Late Mezozoic-Cenozoic evolution of the Arctic Ocean, a problem arises: did this ocean originate as a legacy structure of ancient basins, or did it evolve independently? Solution of this problem requires finding indicators of older oceanic basins within the limits of the Arctic Region. The Arctic Region has structural-material complexes of several ancient oceans, namely, Mesoproterozoic, Late Neoproterozoic, Paleozoic (Caledonian and Hercynian), Middle Paleozoic-Late Jurassic, and those of the Arctic Ocean, including the Late Jurassic-Early Cretaceous Canadian, the Late Cretaceous-Paleocene Podvodnikov-Makarov, and the Cenozoic Eurasian basins. The appearances of all these oceans were determined by a complex of global geodynamical factors, which were principally changed in time, and, as a result of this, location and configuration of newly opened oceans, as well as ones of adjacent continents, which varied from stage to stage. By the end of the Paleozoic, fragments of the crust corresponding to Precambrian and Caledonian oceans were transported during plate-tectonic motions from southern and near equatorial latitudes to moderately high and arctic ones, and, finally, became parts of the Pangea II supercontinent. The Arctic Ocean that appeared after the Pangea II breakup (being a part of the Atlantic Ocean) has no direct either genetic or spatial relation with more ancient oceans.     

The distribution of neodymium isotopes in Arctic Ocean basins

Nd concentration and isotope data have been obtained for the Canada, Amundsen, and Makarov Basins of the Arctic Ocean. A pattern of high Nd concentrations (up to 58 pM) at shallow depths is seen throughout the Arctic, and is distinct from that generally seen in other oceans where surface waters are relatively depleted. A range of isotopic variations across the Arctic and within individual depth profiles reflects the different sources of waters. The dominant source of water, and so Nd, is the Atlantic Ocean, with lesser contributions from the Pacific and Arctic Rivers. Radiogenic isotope Nd signatures (up to ε_Nd = −6.5) can be traced in Pacific water flowing into the Canada Basin. Waters from rivers draining older terrains provide very unradiogenic Nd (down to ε_Nd = −14.2) that can be traced in surface waters across much of the Eurasian Basin. A distinct feature of the Arctic is the general influence of the shelves on the Nd concentrations of waters flowing into the basins, either from the Pacific across the Chukchi Sea, or from across the extensive Siberian shelves. Water-shelf interaction results in an increase in Nd concentration without significant changes in salinity in essentially all waters in the Arctic, through processes that are not yet well understood. In estuarine regions other processes modify the Nd signal of freshwater components supplied into the Arctic Basin, and possibly also contribute to sedimentary Nd that may be subsequently involved in sediment-water interactions. Mixing relationships indicate that in estuaries, Nd is removed from major river waters to different degrees. Deep waters in the Arctic are higher in Nd than the inflowing Atlantic waters, apparently through enrichments of waters on the shelves that are involved in ventilating the deep basins. These enrichments generally have not resulted in major shifts in the isotopic compositions of the deep waters in the Makarov Basin (ε_Nd ∼ −10.5), but have created distinctive Nd isotope signatures that were found near the margin of the Canada Basin (with ε_Nd ∼ −9.0). The deep waters of the Amundsen Basin are also distinct from the Atlantic waters (with ε_Nd = −12.3), indicating that there has been limited inflow from the adjacent Makarov Basin through the Lomonosov Ridge.     

A model for the three-dimensional evolution of continental rift basins,north-east Africa

Large areas of north-east Africa were dominated by regional extension in the Late Phanerozoic. Widespread rifting occurred in the Late Jurassic, with regional extension culminating in the Cretaceous and resulting in the greatest areal extent and degree of interconnection of the west, central and north African rift systems. Basin reactivation continued in the Paleocene and Eocene and new rifts probably formed in the Red Sea and western Kenya. In the Oligocene and Early Miocene, rifts in Kenya, Ethiopia and the Red Sea linked and expanded to form the new east African rift system.This complex history of rifting resulted in failed rift basins with low to high strain geometries, a range of associated volcanism and varying degrees of interaction with older structures. One system, the Red Sea rift, has partially attained active seafloor spreading. From a comparison of these basins, a general model of three-dimensional rift evolution is proposed. Asymmetrical crustal geometries dominated the early phases of these basins, accompanied by low angle normal faulting that has been observed at least locally in outcrop. As rifting progressed, the original fault and basin forms were modified to produce larger, more through-going structures. Some basins were abandoned, others experienced reversals in regional dip and, in general, extension and subsidence became focused along narrower zones near the rift axes. The final transition to oceanic spreading was accomplished in the Red Sea by a change to high angle, planar normal faulting and diffuse dike injection, followed by the organization of an axial magma chamber.     

Association of oil source algae in some Tertiary basins,northern Thailand

A coal petrographic study of sediments, including coals, oil shale, and oil source rocks, in the fossil fuel deposits of northern Thailand revealed changes in alginite associations. In the Lower part of these Tertiary deposits, especially in the Fang oilfield, alginite A (a Botryococcus sp.) was the only type of alga found. Later, the association of Botryococcus braunii, Pila algae, thick-walled alginite B, and temperate palynomorphs were recognized in many coalfields, as well as in the middle part of the deposits in the Fang Basin. Their ages were Late Oligocene (?) to Early Miocene. In the upper part of the fossil fuel deposits, alginite B is dominant in many basins, together with Botryococcus-related taxa such as Pila algae, Reinschia and fresh-water-dwelling ferns. In the Mae Sod Basins Reinschia was found to be dominant in the northern part, whereas lamaginite dominated in the south, showing different environmental conditions in different parts of the basin during deposition. These different associations indicate changes in depositional environments in northern Thailand, resulting from climatic and/or sea level changes during Tertiary time.     

A paleolimnological constraint to the extent of the Last Glaciation on northern Devon Island, Canadian High Arctic

Pre-Holocenelacustrine sediments from a small coastal lake on the TrueloveLowland, northeastern Devon Island,Nunavut Territory, Canada, indicatethat a viable terrestrial ecosystem existed prior to postglacialmarine inundation and subsequent isostatic emergence of thebasin. An AMS ¹⁴C age of 38 kaBP on the basal lacustrine unit provides a preliminarygeochronological framework. This find has directimplications for regional glacial history, becauseit argues against both the Late Wisconsinan glaciation ofcertain coastal lowlands on northern Devon Island,as well as the occupation of Jones Sound by an outlet of theInnuitian Ice Sheet between Devon and Ellesmere islands.     

Burial and thermal history of the West Bashkirian sedimentary basins

The GALO system is applied to the numerical reconstruction of burial and thermal histories of the West Bashkirian lithosphere from the Riphean to the present. An analysis of the variation in tectonic subsidence of the basin during its development is utilized to estimate approximately the mantle heat flow variations. Our variant of basin evolution suggests that after cooling in the Early Riphean, the rather weak thermal reactivations have not led to considerable heating of the lithosphere in the study region. Surface heat flow decreased from relatively high values in the Early Riphean (60–70 mW/m² in the eastern area and 40–50 mW/m² in the western part) to present-day values of 32–40 mW/m². In spite of the relatively low temperature regime of the basin as a whole, a syn-rifting deposition of more than 10 km of limestone, shale and sandstone in the Riphean resulted in rather high temperatures (180–190 °C) at the base of present-day sedimentary blanket in the eastern area. In agreement with the observed data, computed present-day heat flow through the sediment surface increases slightly from 32 to 34 mW/m² near the west boundary of the region to 42 mW/m² near the boundary of the Ural Foldbelt, whereas the heat flow through the basement surface decreases slightly from 28–32 to 24–26 mW/m² in the same direction. The mantle heat flow is only 11.3–12.7 mW/m², which is considerable lower than mean heat flow of the Russian Platform (16–18 mW/m²) and comparable with the low heat flow of Precambrian shields.     

中国北方主要产铀盆地砂岩型铀矿成矿年代学研究

本文通过用铀矿石的U—Ra平衡系数修正样品的铀含量，再进行U—Pb等时线拟合，获得了北方主要产铀盆地的实际成矿年龄：伊犁盆地为12Ma、5～6Ma、1～2Ma；吐哈盆地为48Ma和28Ma；巴彦塔拉凹陷为7Ma；鄂尔多斯盆地东胜地区为107Ma。对含矿砂体中的碎屑钻石与相应蚀源区中酸性火成岩类的锆石U—Pb同位索年龄进行对比，发现含矿砂体的物质成分直接来自中酸性火成岩类的剥蚀产物。该物源是形成富铀砂体的物质基础。通过对蚀源区岩石和盆地含矿地层不同部位砂体岩石样品的U—Pb同位索体系演化特征的研究，论证了可地浸砂岩型铀矿的铀源主要来自两方面，一是蚀源区活性铀含量高的中酸性火成岩类，另一是已经发生铀预富集的沉积砂体。     

中国北方中新生代含铀盆地类型划分

含铀盆地类型划分是铀矿勘查工作的重要基础,目前对北方系列陆相盆地尚未开展过系统的对比研究工作。近年来,独具特色的砂岩型铀矿床跌宕成矿理论、"红-黑"岩系耦合沉积控矿、盆内隆缘控矿等新认识的提出,得益于我国北方砂岩型铀矿床的勘查实践,并在铀矿勘查中不断丰富和拓展应用,取得了一系列重要找矿突破。在此基础上,本文据北方陆相盆地30万余米岩芯勘探成果,以含铀岩系时代和盆地铀富集机理为基础,兼顾盆地构造位置及构造演化,首次提出了中国中新生代含铀盆地类型划分方案,分为三类含铀盆地:复合盆地、叠合盆地和简单盆地。复合盆地其含铀岩系均为中生代构造层;叠合盆地是含铀岩系为中生代和新生代两个构造层的产铀盆地,如准噶尔盆地、柴达木盆地;简单盆地其含铀岩系仅在新生代构造层产出,如龙川江盆地。根据不同含铀盆地类型与构造岩浆岩带的空间分布关系划分为两型,分别为构造岩浆岩带之间的开阔盆地和岩浆岩带内的山间盆地。含铀盆地类型的划分,不仅具有砂岩型铀矿成矿环境、成矿规律及成矿模式研究的重要成因指示意义,也可为目前正在开展的砂岩型铀矿勘查工作提供重要的实践指导。     

北极地区盆地分类与油气资源分布规律

北极地区油气资源潜力大,且油气勘探开发尚处于初期,是未来国内外油气工业发展的重要战略领域。文中综合运用全球领先信息服务公司埃信华迈（IHS）和美国地质调查局（USGS）的最新资料及已有研究成果,对北极地区的盆地类型和油气资源分布规律展开研究。结果表明:北极地区至少发育35个沉积盆地,具体划分为裂谷盆地（5个）、被动大陆边缘盆地（16个）、克拉通盆地（5个）、前陆盆地（5个）和大洋盆地（4个）。裂谷盆地是北极地区油气最富集的盆地类型,发现油气探明和控制可采储量（简称2P储量）441.12×108 t油当量,占北极地区油气总储量的74.6%,其次为前陆盆地、被动大陆边缘盆地和克拉通盆地。北极地区大部分油气储于白垩系、侏罗系和二叠系的碎屑岩储集层,仅有小部分油气储于石炭系和泥盆系碳酸盐岩储集层,且不同国家、不同含油气盆地的主力储集层存在明显差异。北极地区的油气主要源自侏罗系和白垩系的烃源岩,三叠系和泥盆系烃源岩次之。此外,复合圈闭是北极地区油气藏的主要圈闭类型,其次是构造圈闭。北极地区盆地类型和油气宏观分布规律的研究将为中国石油公司在北极地区的长远发展奠定基础。      

Late Pleistocene and Holocene vegetation and climate on the northern Taymyr Peninsula, Arctic Russia

Pollen data from a Levinson-Lessing Lake sediment core (74°28'N, 98°38'E) and Cape Sabler, Taymyr Lake permafrost sequences (74°33'N, 100°32'E) reveal substantial environmental changes on the northern Taymyr Peninsula during the last c. 32 000 [Formula: See Text]C years. The continuous records confirm that a scarce steppe-like vegetation with Poaceae, Artemisia and Cyperaceae dominated c. 32 000-10 300 [Formula: See Text]C yr BP, while tundra-like vegetation with Oxyria, Ranunculaceae and Caryophyllaceae grew in wetter areas. The coldest interval occurred c. 18 000 yr BP. Lateglacial pollen data show several warming events followed by a climate deterioration c. 10 500 [Formula: See Text]C yr BP, which may correspond with the Younger Dryas. The Late Pleistocene/Holocene transition, c. 10 300-10 000 [Formula: See Text]C yr BP, is characterized by a change from the herb-dominated vegetation to shrubby tundra with Betula sect. Nanae and Salix. Alnus fruticosa arrived locally c. 9000-8500 [Formula: See Text]C yr BP and disappeared c. 4000-3500 [Formula: See Text]C yr BP. Communities of Betula sect. Nanae, broadly distributed at c. 10 000-3500 [Formula: See Text]C yr BP, almost disappeared when vegetation became similar to the modern herb tundra after 3500-3000 [Formula: See Text]C yr BP. Quantitative climate reconstructions show Last Glacial Maximum summer temperature about 4°C below the present and Preboreal (c. 10 000 [Formula: See Text]C yr BP) temperature 2-4°C above the present. Maximum summer temperature occurred between 10 000 and 5500 [Formula: See Text]C yr BP; later summers were similar to present or slightly warmer.     

Postglacial emergence and Late Quaternary glaciation on northern Novaya Zemlya, Arctic Russia

Recent observations on postglacial emergence and past glacier extent for one of the least accessible areas in the Arctic, northern Novaya Zemlya are here united. The postglacial marine limit formed 5 to 6 ka is registered on the east and west coasts of the north island at 10 ± 1 and 18 ± 2 m aht, respectively. This modest and late isostatic response along with deglacial ages of >9.2 ka on adjacent marine cores from the northern Barents Sea indicate either early (>13 ka) deglaciation or modest ice sheet loading (<1500 m thick ice sheet) of Novaya Zemlya. Older and higher (up to 50 m aht) raised beaches were identified beneath a discontinuous glacial drift. Shells from the drift and underlying sublittoral sediments yield minimum limiting ¹⁴C ages of 26 to 30 ka on an earlier deglacial event(s). The only moraines identified are within 4 km of present glacier margins and reflect at least three neoglacial advances in the past 2.4 ka.     

南海北部陆缘盆地形成的构造动力学背景

摘要：南海北部陆缘盆地处于印度板块与太平洋及菲律宾海板块之间,但三大板块对南海北部陆缘盆地的影响是不同的。通过对三大板块及古南海演化的研究,可知南海北部陆缘地区应力环境于晚白垩世发生改变。早白垩世处于挤压环境,晚白垩世以来转变为伸展环境并且不同时期的成因不同。晚白垩世-始新世,华南陆缘早期造山带的应力松弛、古南海向南俯冲及太平洋俯冲板块的滚动后退导致其处于张应力环境。始新世时南海北部陆缘裂陷盆地开始产生,伸展环境没有变,但因其是由太平洋板块向西俯冲速率的持续降低及古南海向南俯冲引起的,南海北部陆缘盆地继续裂陷。渐新世-早中新世,地幔物质向南运动及古南海向南俯冲导致南海北部陆缘地区处于持续的张应力环境;渐新世早期南海海底扩张;中中新世开始,三大板块开始共同影响着南海北部陆缘盆地的发展演化。     

An early Holocene caribou antler from northern Ellesmere Island, Canadian Arctic Archipelago

During the last glaciation of northern Ellesmere Island many areas remained ice-free. A caribou antler from deglacial-marine sediments in Clements Markham Inlet dates 8,415 ± 135 B.P. (S-2501). If locally derived it places caribou at the northern limit of their contemporary range at the onset of deglaciation in this area. Immediately to the south, on the Hazen Plateau, ice remained at its limit until c . 8,000 B.P. Therefore, this antler may indicate the presence of caribou during full glacial time.     

A linked fold-thrust model for the deformation of the Tennant Creek goldfield,northern Australia

Several major shear zones trending WNW through the southern Tennant Creek goldfield show evidence for south up over north (reverse) movement during low temperature brittle-ductile shear. Total vertical displacements across two of these shears are around 1 km based on the apparent offset of a concordant porphyry. A thin-skinned linked fold-thrust model for the early deformation of the Tennant Creek goldfield is supported by the disharmonie fold profile shapes, the subhorizontal enveloping surface of folding and a shallow and relatively planar basement topography inferred from two-dimensional gravity modelling. Massive iron oxide deposits within the Warramunga Group, which host gold, copper and bismuth ore, formed during folding and reverse faulting, but the shear zones are neither unusually altered nor mineralised compared to the surrounding rocks emphasising the importance of chemical controls on ironstone formation, such as hematite-rich layers in the stratigraphy, rather than direct structural controls.     

A new palaeoenvironmental model for the evolution of the Byzovaya Palaeolithic site,northern Russia

Recently, the sediment stratigraphy and geochronology of the well‐known Palaeolithic site Byzovaya in northern Russia were investigated. New technological analyses of the artefacts suggest a Middle Palaeolithic Mousterian culture, and occupation by Neanderthals, not Modern humans as previously thought. We present here a new and detailed documentation of the stratigraphy, including the geological context of the artefacts and faunal remains. From sedimentological criteria we confidently interpret the find‐bearing strata as debris‐flow deposits, covered by aeolian sediments. The chronology is based on radiocarbon and luminescence (OSL) dates from the find‐bearing and overlying strata. The results are utilized to reconstruct the geological history at the excavation area. The stratigraphy varies considerably across the excavation area. The most intact and undisturbed part of the sequence was found inside the most recent Excavation II. In this part the artefacts and bones appear to have been permanently sealed and protected by aeolian sand. The older Excavation I shows a more complicated stratigraphy, as the finds may have been temporarily exposed during the early Holocene owing to ravine incision and slumping activity. The individual radiocarbon dates that were collected from different parts of the site and from various stratigraphic positions are re‐investigated in this study. By using Bayesian statistics the conclusion is that the site was occupied during a restricted period around 30.6–34.7 ka. A series of partly unpublished OSL dates of coversand from different sites demonstrates a regional aeolian signal during the Lateglacial in northern Russia, 15–14 ka.     

Dynamics of the Arctic and adjacent petroleum basins: a record of plume and rifting activity

The Late Paleozoic and Mesozoic history of high-latitude petroleum and coal basins is investigated and compared with the history of plume magmatism in the same areas. The sedimentation rates in all discussed cases are proven to be the fastest (more than 100 m per 1 Myr) during rifting events. Other peaks of rapid deposition may be associated with collisional mountain growth and/or climate change.     

A new model of Pleistocene glaciation in the northern Urals

This is an overview of the latest data on the age of topographically expressed glacigenic formations of the Polar Urals obtained by international geological teams by modern dating techniques including optical luminescence, radiocarbon and cosmogenic beryllium in exposed boulders. The new dates combined with the results of geological mapping and remote sensing data is a basis for rejecting the concept of the Quaternary Uralian ice caps in favor of small alpine glaciers which developed south of the Kara ice sheet.     

试论鄂尔多斯北部中新生代盆地砂岩型铀矿找矿前景

本文概述了鄂尔多斯盆地北部地区区域地层、构造运动、地质发展历史，水文地质特征，运用层间氧化带砂岩型铀矿的成矿理论和找矿准则，分析本区的找矿前景和重点找矿对象，提出了工作建议。