华北中部岩石圈电性结构——应县—商河剖面大地电磁测深研究

20 0 1年, 沿着山西应县到山东商河, 重新布置大地电磁测深剖面进行研究.采用现代先进的大地电磁数据处理技术和快速松弛二维反演方法获得该剖面二维电性结构模型, 从而充分展示了华北地区岩石圈电性结构的特点.从电性特征上讲, 华北岩石圈以太行山前断裂为界划分为东、西两区, 东区为低阻区, 西区为高阻区.在东区, 上地壳电性结构基本与华北裂谷系的隆、坳构造格局相对应, 岩石圈的电导最高达3× 104 S, 远远大于强烈活动的安第斯山岩浆弧区和西藏高原岩石圈的电导.这里, 在构造连接部位的地壳中有不连续的高导体存在, 电导率大约0.1~ 0.8S/m.在西区, 太行山和恒山的岩石圈为高阻块体, 表现出稳定大陆区岩石圈导电性结构的特点.但恒山高阻块体之下发现一组向西缓倾的高导层, 其电导率为0.0 4~0.2 5S/m, 顶面在2 0km深处, 底面深度大约40km.      

大陆岩石圈导电性的研究方法

随着地球科学的进展 ,大陆岩石圈导电性结构的研究越来越引起人们的重视 ,而超宽频带大地电磁测深则是目前用于探测岩石圈导电性最有效的地球物理先进技术。它把现代性能优良的宽频带大地电磁系统 (MT 2 4NS或V5 2 0 0 0 )与长周期智能化大地电磁系统 (LIMS)配套使用 ,采集地面上频率范围为n× 10 -4～n× 10 2 Hz的天然电磁场信号 ,并通过一系列数据处理和反演计算 ,获得深达下地壳和上地幔的地下导电性结构模型。此模型不仅可以提供有关岩石圈地质构造轮廓的信息 ,更重要的是可以间接反映现今地下深部的热结构特征和物质状态分布特点。多年来 ,应用超宽频带大地电磁测深对青藏高原岩石圈导电性结构的研究表明 ,高原的中、下地壳确实是良导电性的 ;它可能说明西藏地壳中普遍存在岩石的局部熔融 ,或地热流体。沿着应县—商河剖面的大地电磁测深研究结果从电性的角度证明了太行山山前断裂为一组向东倾斜的深断裂 ,华北地区岩石圈以其为界划分为东、西两区 ;东区为低阻区 ,与构造活动区的岩石圈导电性特征相符 ;西区为高阻区 ,表现出稳定大陆区岩石圈导电性结构的特点。     

华北地区东部岩石圈导电性结构研究——减薄的华北岩石圈特点

华北古大陆克拉通解体、岩石圈减薄的深部过程,对于建立中国大陆中新生代演化动力学模型是亟待深入研究的重要科学问题,因而"华北克拉通破坏"也就成了当前学术界的热门话题。为了研究"华北克拉通破坏"首先需要给出较准确的华北岩石圈结构,这必须依靠包括超宽频带高精度大地电磁深探测在内的现代深部地球物理探测技术。2001和2005年在华北地区东部布置了应县—商河(HB-MT01)、文水—日照(HB-MT02)大地电磁测深剖面进行研究。研究结果表明,在华北地区东部沿地壳-上地幔探测剖面可划分为4个电性区,区内发现有下地壳高导带和上地幔高导层存在。文中依据研究区壳-幔电性结构特征,推断华北地区东部地壳和上地幔之间发生过大规模构造运动,导致壳-幔之间存在解耦现象。研究结果还发现,华北东部确实存在岩石圈减薄区,其岩石圈厚度约50~80km厚。岩石圈明显减薄的区域包括北太行山隆起、华北裂谷带北部和鲁西断隆,其范围比原先认识到的要复杂,并非以太行山重力梯度带为界划分东、西两区,简单地认为东区即是减薄区。此外,在华北地区东部的现代高精度大地电磁探测结果也进一步证明了地球物理观测对于大陆动力学研究的重要性,这使人们更加认识到在今后的研究中必须强调地球物理-地质-地球化学之间的有机结合。     

长江中下游南京（宁）-芜湖（芜）段深部壳幔电性结构——宽频大地电磁测深研究

为了较全面、客观地认识南京(宁)-芜胡(芜)地区岩石圈深部结构,探讨岩石圈热结构和壳、幔物质状态等重要科学问题,为矿集区成矿作用和成矿规律的研究提供依据,我们完成了6条宽频大地电磁测深剖面。通过分析各剖面电性成像结果,讨论了研究区地壳-上地幔导电性的"拟三维"结构,发现测区普遍存在连续的下地壳-上地幔低阻层,仅在巢湖冲褶体断开。结合区域热流结果,我们认为下地壳-上地幔有较好的导电性,可能存在局部"熔融体"或"含水剪切断裂",其物质状态很可能是热的、软弱的。此外,我们通过物质状态和电性界面推断了上地幔隆起的位置和长江深断裂带的分布范围,认为长江断裂带不但存在,而且由多条北深南浅的断裂组成,较为复杂。     

中国大陆地壳上地幔不均匀性与矿产资源预测

在充分收集、整理、综合研究中国大陆11条地学断面(简称GGT)、数十条其它地球物理剖面(地震剖面、大地热流、大地电磁测深等剖面)和覆盖中国大陆及邻区的剪切波三维速度结构资料的基础上,阐述了中国大陆及邻区地壳结构、岩石圈结构和软流圈结构,并对中国大陆矿产资源预测作了简单的讨论。中国岩石圈结构是在三种不同性质的软流圈基础上发展起来的,有明显的继承性。中国岩石圈结构在某种程度上与大地构造单元相吻合,说明地壳构造受到岩石圈的影响和制约。尤其在地震波垂向低速带上(地壳上地幔都表现为低速性质)是内生多金属矿带的良好产出环境。     

大地电磁测深(MTS)用于研究地壳上地幔的初步成果

地质矿产部物化探研究所自1980年先后完成了青藏、川滇、华南、甘肃、新疆、内蒙、山西、松辽、长江中下游、秦岭等地区的深大地电磁测深剖面约6800km。得出了剖面通过地区地壳、上地幔的电性结构,研究了各电性单元与地质构造单元的关系,对发现的地壳、上地幔内低阻层的成因进行了探讨。根据已掌握的深大地电磁数据编制了中国大陆电性图件,得出中国大陆岩石圈的平均厚度为100～120km,东部地区薄,西部地区厚的结论。利用高温高压岩石电阻率测定结果,粗略地给出了剖面通过地区岩石圈内主要的物质组成。     

华南地区进贤-柘荣剖面深部电性结构

为了研究华南地区的深部电性结构,探寻浅部地质过程的深部背景,布设了江西进贤至福建柘荣超长周期大地电磁测深剖面。通过剖面数据的处理、定性分析及二维反演,获得剖面岩石圈尺度的电性结构模型,并分区块对壳幔电性结构及主要断裂进行了分析。反演结果表明：1）剖面可分为4个构造单元,分别为江南造山带、华夏地块内部、华夏褶皱带和东南沿海岩浆岩带;2）武夷山与东南沿海岩浆岩带两处电性莫霍面隆起,电性莫霍面的起伏特征受控于区域深大断裂;3）剖面电性岩石圈整体表现为西薄东厚,江南造山带岩石圈-软流圈界面埋深为80~100 km,华夏褶皱带及东南沿海岩浆岩带的岩石圈-软流圈界面埋深约为140 km,存在一处岩石圈减薄区和两处软流圈上涌区,反映了伸展构造作用对岩石圈的不均匀改造。     

基于MapGIS组件二次开发MT成果数据的查询及应用

为了方便快捷地利用大地电磁测深来研究深部地壳和上地幔岩石圈层的信息,这里以首次建立的大地电磁测深成果MicrosoftSQLSever数据库为基础,结合VisualBasic语言与MapGIS组件二次开发技术,实现了大地电磁测深成果的空间数据和属性数据信息的查询等功能,其可为不同研究区的岩石圈壳幔电性结构特征的研究提供便捷的技术支持。同时以长江中下游重要成矿区带为例,利用大地电磁测深成果数据的查询功能,开展了岩石圈电性结构的初步研究,并取得了一定的应用效果。     

中国大陆特大型矿床地球物理背景研究

在研究中国数10条地球物理剖面(地震、大地热流、大地电磁测深剖面)和中国大陆及邻区剪切波三维速度结构资料的基础上,给出中国大陆地壳上地幔三维结构模型。讨论了中国特大型矿床产出的深部地球物理背景。指出特大型矿床虽然为数极少,但也具有成“点”“带”“面”的分布特征。大多数大中小矿床分布在不同构造单元的边界附近。特大型内生多金属矿床主要产在岩石圈地幔减薄部位、软流圈上隆(地震波垂向低速)区、地壳上地幔的横向不均匀区的变换带(地壳上地幔薄弱     

东北地区新生代火山作用-深部作用与大陆裂谷型盆地

新生代火山岩含有丰富的上地幔岩包休和高压巨晶，火山岩系列、岩石类型、痕量元素等特征以及空间分布特征和与俯冲作用有关的中生代火山岩截然不同，其岩石学特征及热力学研究等表明它们形成于大陆裂谷构造环境。根据出露地表的古老的变质岩系和新生代玄武岩中的上地幔岩包体的岩石学特征以及热力学计算，建立了陆壳一上地幔结构岩石学剖面，新生代岩石圈拉伸，软流圈上隆，为一减薄的陆壳结构，形成了下辽河等一些大陆裂谷型盆地。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)