Passive and active margin history of the northern Tatricum (Western Carpathians, Slovakia)

The Tatricum, an upper crustal thrust sheet of the Central Western Carpathians, comprises pre-Alpine crystalline basement and a Late Paleozoic–Mesozoic sedimentary cover. The sedimentary record indicates gradual subsidence during the Triassic, Early Jurassic initial rifting, a Jurassic–Early Cretaceous extensional tectonic regime with episodic rifting events and thermal subsidence periods, and Middle Cretaceous overall flexural subsidence in front of the orogenic wedge prograding from the hinterland. Passive rifting led to the separation of the Central Carpathian realm from the North European Platform. A passive margin, rimmed by peripheral half-graben, was formed along the northern Tatric edge, facing the Vahic (South Penninic) oceanic domain. The passive versus active margin inversion occurred during the Senonian, when the Vahic ocean began to be consumed southwards below the Tatricum. It is argued that passive to active margin conversion is an integral part of the general shortening polarity of the Western Carpathians during the Mesozoic that lacks features of an independent Wilson cycle. An attempt is presented to explain all the crustal deformation by one principal driving force – the south-eastward slab pull generated by the subduction of the Meliatic (Triassic–Jurassic Tethys) oceanic lithosphere followed by the subcrustal subduction of the continental mantle lithosphere.     

应用磁异常信号监测填埋体位移的技术研究

在比较填埋场内部位移监测方法的基础上,提出利用增强填埋场内目标体所产生的磁异常信号(磁通量密度,以ΔT计)观测填埋体位移的方法. 建立正演模型,研究目标体磁异常信号的理论曲线变化特征及其在不同环境条件下的信号变化规律. 对ΔT实测值分析表明,填埋场环境背景值(-100～100 nT)并不会掩盖特征目标体磁异常信号的最大理论值(724.31～2 804.24 nT),确定了该方法的可行性. 模拟表明,在规定目标体大小、磁化强度的条件下,当目标体埋深为1～2 m时,其水平位置定位误差≤0.02 m,竖直位置定位误差≤0.09 m,证实了磁测定位方法具有良好的应用前景.      

Avian magnetic compass: fast adjustment to intensities outside the normal functional window

To determine how fast birds can adapt to magnetic intensities outside the normal functional window of their magnetic compass, we tested migratory birds in a magnetic field of 92,000 nT, twice the intensity of the local geomagnetic field at the test site in Frankfurt a.M., Germany. In the local field, robins showed a significant preference of their southerly migratory direction, whereas in the 92,000-nT field, they were initially disoriented. However, when the birds were preexposed to 92,000 nT for 1 h before being tested, they were able to orient under this intensity, and their behavior did not differ from that in the geomagnetic field. These data show that birds require only a short time to adjust to magnetic intensities, which they cannot spontaneously use for orientation. Interpreting these findings in view of the radical pair model (Ritz et al. 2000), this means that they can learn rather quickly to interpret novel activation patterns on their retina.     

华北地区下古生界海相碳酸盐岩二次生烃作用机理研究

我国下古生界海相碳酸盐岩中有机质由于形成时间早，经历了漫长的地质历史演化，一部分有机质深埋已形成了烃类，由于后期构造运动抬升则停止了生烃过程，但当再次深埋时，源岩干酪根受热温度超过一次生烃温度时，源岩又开始第二次生烃。本文对我国古老的下古生界海相碳酸盐岩的二次生烃作用及其机理进行了较为详尽的研究。     

浙江遂昌柘岱口-湖山断裂带活动期次与萤石成矿关系

遂昌柘岱口一湖山北东向断裂带在晚侏罗世至晚白垩世晚期经历了多期次、不同性质的活动，断裂活动与该地区两个大规模萤石矿田的形成关系密切。晚侏罗世晚期到早白垩世早期断裂活动表现为拉张松驰作用，为黄沙腰萤石矿田的形成提供了导矿和容矿构造空间，萤石矿主体赋存于北东向断裂带内。晚白垩世晚期，断裂活动表现为挤压环境，断裂带具有导矿作用，矿体受控于派生之北西向次级断裂内，湖山萤石矿田的形成具有此特征。     

关于浙东塘上组的时代问题

浙东塘上组中、下部火山岩的沉积夹层中首次发现?Halysestheria叶肢介及孢粉化石,并找到Pseudofrcneloysis parceramosa与P.cf.rapillosa为主的植物化石。本文综合各门类化石所反映的地质时代,认为浙东塘上组应归属早白垩世晚期。这与剖面上获得的同位素年龄值(110 Ma)相吻合。塘上组层位与邻区石帽山群上组、禾口组(闽),周家店组(赣东),徽州组上部(皖南)及葛村组上部(江苏)相当。     

西昆仑库科西鲁克地区基性岩脉地球化学及构造意义

新疆库科西鲁克地区广泛发育基性岩脉,多呈岩墙、岩枝和小岩滴。基性岩脉岩石类型为辉长岩和辉绿岩。辉长岩属于碱性玄武岩,而辉绿岩属于过铝质碱性系列碱玄武岩与粗面玄武岩过渡型,其形成深度(浅成相)比辉长岩浅(中深成相)。区内基性岩脉形成于闭合边缘岛弧、活动陆缘造山带环境,是由幔源原生岩浆经过分异并同化混染地壳物质而形成,结晶分异是控制岩浆演化的主要因素。辉长岩中δEu具有弱的亏损。辉绿岩δEu为正异常,而C e均具弱亏损,成岩氧逸度较高,其成因与典型的I型花岗岩类相似,为壳幔混合型。辉长岩偏幔源,而辉绿岩偏壳源,可能为幔源岩浆上侵受围岩混染所致。辉长岩年龄(119 M a)要比辉绿岩年龄(46.1M a)老,辉长岩为冈底斯陆块向欧亚大陆板块碰撞拼贴过程中,逆冲挤压结束的标志,辉绿岩为大规模逆冲挤压剪切结束,青藏高原隆升初期拉张作用的产物。     

相山矿田铀矿地质研究进展与趋势

相山铀矿是华南最大的产于火山-侵入杂岩体中的热液脉型铀矿田。文章对相山铀矿地质研究的历史进行了简略回顾,重点阐述了铀矿地质研究的新进展,主要有:火山杂岩时代为早白垩世、火山岩浆具有反方向演化特点,成矿作用是一个相对连续的演化过程,铀矿类型归属斑岩型,属于与燕山晚期火山-斑岩作用有关的铀或铀-多金属矿床成矿系列。最后,文章展望了未来的研究方向。     

Tracking pigeons in a magnetic anomaly and in magnetically “quiet” terrain

Pigeons were released at two sites of equal distance from the loft, one within a magnetic anomaly, the other in magnetically quiet terrain, and their tracks were recorded with the help of GPS receivers. A comparison of the beginning of the tracks revealed striking differences: within the anomaly, the initial phase lasted longer, and the distance flown was longer, with the pigeons' headings considerably farther from the home direction. During the following departure phase, the birds were well homeward oriented at the magnetically quiet site, whereas they continued to be disoriented within the anomaly. Comparing the tracks in the anomaly with the underlying magnetic contours shows considerable differences between individuals, without a common pattern emerging. The differences in magnetic intensity along the pigeons' path do not differ from a random distribution of intensity differences around the release site, indicating that the magnetic contours do not directly affect the pigeons' routes. Within the anomaly, pigeons take longer until their flights are oriented, but 5 km from the release point, the birds, still within the anomaly, are also significantly oriented in the home direction. These findings support the assumption that magnetically anomalous conditions initially interfere with the pigeons' navigational processes, with birds showing rather individual responses in their attempts to overcome these problems.     

The isostatic state of the southern Urals crust

The Uralide orogen, in Central Russia, is the focus of intense geoscientific investigations during recent years. The international research is motivated by some unusual lithospheric features compared with other collisional belts including the preservation of (a) a collisional architecture with an orogenic root and a crustal thickness of 55–58 km, and (b) large volumes of very low-grade and non-metamorphic oceanic crust and island arc rocks in the upper crust of a low–relief mountain belt. The latter cause anomalous gravity highs along the thickened crust and the isostatic equilibrium inside the Uralides lithosphere as well as the overthrust high-metamorphic rocks. The integrated URSEIS '95 seismic experiment provides fundamentally new data revealing the lithospheric architecture of an intact Paleozoic collisional orogen that allows the construction of density models. In the Urals' lithosphere different velocity structures resolved by wide-angle seismic experiments along both the URSEIS '95- and the Troitsk profile. They can be used to constrain lithospheric density models: a first model consists of a deep subducted continental lower crust which has been highly eclogitized at depths of 60–90 km to a density of 3550 kg/m³. The second model shows a slightly eclogitized lower crust underlying the Uralide orogen with a crustal thickness of 60 km. The eclogitized lower crust causes a too-small impedance contrast to the lithospheric mantle resulting in a lack of reflectors in the area of the largest crustal thickness. Both models fit the measured gravity field. Analyzing the isostatic state of the southern Urals' lithosphere, both density models are in isostatic equilibrium.     

喀斯特地区典型风化剖面重金属超标程度及元素迁移特征研究

我国西南喀斯特地区是著名的重金属元素地球化学异常区。除了人类活动所导致的土壤污染问题以外,地质背景很可能是造成土壤重金属超标的重要因素。为了弄清岩石风化和成土过程中重金属的释放规律及其环境效应,本次研究以贵州省罗甸县典型的碳酸盐岩和碎屑岩风化剖面为载体,采用实地调查、地球化学测试分析等手段,结合质量平衡系数的计算方法对研究剖面的重金属元素超标程度及元素迁移规律展开调查。研究结果表明:碳酸盐岩比泥质岩具有更高的重金属元素释放潜能,其风化和成土过程向环境中释放重金属的量与风化壳的发育程度有关。研究区石灰土剖面重金属元素超标程度严重,且以Cd和As的超标程度最大。地带性黄壤中Cr、Ni元素的富集很可能与剖面发育过程中铁氧化物的沉淀富集有关。综合分析认为岩性不同所导致的风化速率的差异很可能是造成碳酸盐岩和泥质岩剖面重金属淋失程度差异的主要原因。而且,重金属元素在风化剖面中的迁移规律受元素自身地球化学性质、母岩类型和风化壳发育程度等多重因素控制。     

安徽栏杆地区橄榄辉长岩地球化学特征及其与金刚石成矿的关系

安徽栏杆地区碱性基性岩岩性为橄榄辉长岩,微量元素特征表现为大离子亲石元素(K、Rb、Sr、Th和Ba)富集,但高场强元素(Nb、Ta、Zr和Hf)无明显亏损,表明岩石形成于大陆板内环境,为地幔低度部分熔融的产物;稀土元素特征表现为LREE强烈富集,而HREE相对亏损,暗示了源区富集特征,Eu负异常显示岩浆经历了明显的斜长石结晶分异。结合中国东部碱性基性岩的金刚石成因条件及地球化学特征分析,认为本区碱性基性岩具有金刚石成矿地质条件。     

雁荡山自然景观的科学价值

雁荡山是一座白垩纪复活破火山，经断裂切割抬升而成为典型性的破火山立体模型。它向人们展示了破火山内部的各种地质要素和各类岩石的相互关系，提供了破火山喷发产物与中央侵入体有直接联系的证据。涵盖了流纹质岩浆火山爆发、喷溢、侵出、侵入等的完整过程，堪称流纹质火山岩类的天然博物馆。雁荡山不仅显现了白垩纪时期亚洲大陆边缘复活型破火山形成与演化的地质过程，而且是古太平洋伊泽奈奇（ｌｚａｎａｑｉ）板块向亚洲大陆俯冲、壳幔深部作用的一种地表标志性展示。雁荡山破火山的奇特景观代表着东亚亚热带滨海山岳地质生态模式、奇特优秀的自然景观、具普遍意义的杰出科学价值和浓厚的民族山水文化，三者交融在一起，构成了雁荡山所特有的世界上独一无二的、兼符自然与文化双重标准的自然遗产。     

应用地球物理方法研究撞击坑

陨石的撞击作用使靶岩形成一个特殊的地球物理场，具有低密度、低电阻率、低速度、磁力异常等不同于周边的岩性。因此，可利用重力、电法、磁法、地震等地球物理方法探测撞击坑的形态特征和寻找新的冲击构造。     

唐古拉坳陷中-新生代高钾钙碱性火山岩及其成岩构造环境

藏北唐古拉坳陷中央隆起带与北部凹陷带海相体罗－白垩纪地层中，夹杂一套以高钾安山岩、高铝玄武岩为主体的高钾钙碱性火山岩系列。主要岩石类型有玄武岩、高铝玄武岩、高钾安山岩、英安岩、流纹岩及流纹质角砾凝灰岩。根据火山岩产出特征和全岩同位素年龄测定，将本区火山活动划分为中生代晚期和老第三纪两个旋回。这套火山岩系的REE、相容元素和不相容元素分布特点与造山带火山岩类似；在构造判别图解上，其投影点均落在造山带大山岩区域内。对火山岩特征分析表明，它们的形成与俯冲作用有关，显示出在俯冲造山带的构造背景下演变而来。     

论蓬家夼金矿基础地质──答杨金中等商榷之疑

蓬家夼金矿容矿地层为下白垩统莱阳群一段含碳碎屑岩系 ,与世界上已知的产于含炭岩系金矿床对比 ,以容矿地层时代新、陆相沉积及未经变质区别于已知的金矿床而认为是一种新类型金矿。笔者依据蓬家夼金矿控矿条件 ,成功预测并找到新的盲金矿床 (宋家沟 -发云夼金矿 )。本文论证蓬家夼金矿基础地质 ,指出杨金中等《论蓬家夼金矿的地质特征及成因与聂爱国等商榷》一文基础地质中的错误 :将莱阳群一段含碳碎屑岩错认为荆山群变质杂岩 ,将沉积碎屑岩误认为滑脱构造岩 ,从而导致对该矿床成因的错误认识     

对壳幔二元混合模型的讨论

壳幔二元混合模计算结果的意义是多解的。对该模型所获得的“壳幔比”,并不象一些研究者所认为并强调的那样具有定量意义。所以,将f_M视为岩浆形成时地幔物质直接参与的质量比是不正确的;实质上,它只能被用来定性地反映岩浆源区岩石的成熟程度。     

胶莱盆地一种新金矿类型——蓬家夼式金矿床研究

赋存于胶莱盆地下白垩统莱阳组含碳碎屑岩系中的蓬家夼式金矿床与金矿化 ,无论其形成地质时代还是岩石特征或沉积环境 ,均与国内外已知的金矿不同 ,为一种新类型金矿床。本文阐述了蓬家夼式新类型金矿床的地质特征 ,并论述了其成因 ,认为其为一种沉积 -改造作用形成的新类型金矿床。     

在壳幔作用过程中Sr含量对岩浆岩Sr同位素组成的影响──兼论东南沿海白垩纪双峰式火山岩成因

在壳幔作用道程中，壳幔源岩浆常会发生一定程度的混合，而它们Sr含量的差异会对混合岩浆的Sr同位素组成产生重大影响。本文简要介绍壳幔源岩浆的Sr含量差异对形成大陆型等同位素组成的双峰式火山岩的制约、幔源基性岩浆岩高（87Sr／86Sr）i的可能成因、岩浆混合程度的定量汁算及壳幔相互作用的一些最新的观点与研究成果，并讨论东南沿海白垩纪等同位素组成的双峰式火山岩的成因．指出基性端员玄武岩起源于上地幔楔．其高的Sr含量和高（87Sr／86Sr）i归因于地幔源区受到了俯冲板决的深海沉积物的参与，而酸性端员流纹岩岩浆由古老变质基底部分熔融生成的初始熔体与少量（5～6％）玄武质岩浆混合而成，并由于后者Sr含量近高于前者而使混合成因的流纹岩岩浆之（87Sr／86Sr）i明显低于古老变质基底而接近于玄武岩。     

冀北沽源盆地中生代火山岩的同位素年龄及成因

根据同位素年龄测定,冀北地区张家口组三段酸性火山岩的形成年龄为138Ma,属于上侏罗统顶部;花吉营组中基性岩石的形成年龄为133Ma,应划归下白垩统底部为宜。根据火山岩全岩Pb—Pb等时线年龄、残留锆石的年龄及基底岩石的变质时代等信息,结合火山岩中稀土元素的分布特征等推断:张家口组火山岩主要是由基底岩石(硅铝壳)重熔形成,而花吉营组岩石可能为壳幔混染成因。