华南巨型锑矿带的特征及其制约因素   总被引：5，自引：0，他引：5       下载免费PDF全文

刘建明  顾雪祥  刘家军  郑明华 《地球物理学报》1998,41(Z1):207-215

华南巨型锑矿带位于中国南方扬子陆块与华夏陆块的接合过渡地段,锑矿床都产在沉积地层中,具有显著的层控性,常有整合的层状矿体出现,赋矿地层都显示异常高的锑丰度,充分显示了与沉积盆地演化密不可分的内在联系矿石的硫同位素受赋矿地层层位和沉积相的控制,碳同位素特征反映了深部因素与浅部过程的耦合,铅同位素则暗示研究区地层及其中锑矿化的亲缘关系和统一演化历史．锑是一个趋于在地壳浅部富集的中低温热液成矿元素,因此成熟度越高的地壳块段锑的丰度越高,锑矿产出概率也越大．华南巨型锑矿带的形成乃是扬子陆块南缘沉积盆地长期演化的结果,可能与这一岩石圈块段长期以来强烈的物质分异和再循环有关．  相似文献   

Stress in the lithosphere: Inferences from steady state flow of rocks   总被引：9，自引：0，他引：9  

Jean-Claude C. Mercier  Douglas A. Anderson  Neville L. Carter 《Pure and Applied Geophysics》1977,115(1-2):199-226

Mechanical data and flow processes from steady state deformation experiments may be used to infer the state of stress in the lithosphere and asthenosphere. Extrapolations of flow equations to a representative geologic strain rate of 10^–14/sec. for halite, marble, quartzite, dolomite, dunite and enstatolite are now warranted because the steady state flow processes in the experiments are identical to those in rocks and because the geotherms are reasonably well established. More direct estimates are obtained from free dislocation densities, subgrain sizes and recrystallized grain sizes all of which are functions only of stress. Using the last of these techniques, we have estimated stress profiles as a function of depth from xenoliths in basalts and kimberlites, whose depths of equilibration were determined by pyroxene techniques, from four different areas of subcontinental and suboceanic upper mantle. The results are similar and indicate stress differences of about 200 to 300 bars at 40 to 50 km, decaying to a few tens of bars at depths betow 100 km. These stresses are reasonable and are in accord with extrapolations of the mechanical data provided that allowance is made for a general increase in strain rate and decrease in viscosity with depth.  相似文献   

Cenozoic uplift of Variscan Massifs in the Alpine foreland: Timing and controlling mechanisms   总被引：3，自引：0，他引：3  

P.A. Ziegler  P. Dzes 《Global and Planetary Change》2007,58(1-4):237

The European Cenozoic Rift System (ECRIS) and associated fault systems transect all Variscan Massifs in the foreland of the Alps. ECRIS was activated during the Eocene in the foreland of the Pyrenees and Alps in response to the build-up of collision-related intraplate stresses. During Oligocene and Neogene times ECRIS evolved by passive rifting under changing stress fields, reflecting end Oligocene consolidation of the Pyrenees and increasing coupling of the Alpine Orogen with its foreland. ECRIS is presently still active, as evidenced by its seismicity and geodetic data.Uplift of the Massif Central and the Rhenish Massif, commencing at the Oligocene–Miocene transition, is mainly attributed to plume-related thermal thinning of the mantle–lithosphere. Mid-Burdigalian uplift of the SW–NE-striking Vosges–Black Forest Arch, that has the geometry of a doubly plunging anticline breached by the Upper Rhine Graben, involved folding of the lithosphere. Late Burdigalian broad uplift of the northern parts of the Bohemian Massif reflects lithospheric buckling whereas late Miocene–Pliocene uplift of its marginal blocks involved transpressional reactivation of pre-existing crustal discontinuities. Crustal extension across ECRIS, amounting to no more than 7 km, was compensated by a finite clockwise rotation of the Paris Basin block, up warping of the Weald–Artois axis and reactivation of the Armorican shear zones. Intermittent, though progressive uplift of the Armorican Massif, commencing in the Miocene, is attributed to transpressional deformation of the lithosphere.Under the present-day NW-directed compressional stress field, that came into evidence during the early Miocene and further intensified during the Pliocene, the Armorican Massif, the Massif Central, the western parts of the Rhenish Massif and the northern parts of the Bohemian Massif continue to rise at rates of up to 1.75 mm/y whilst the Vosges–Black Forest arch is relatively stable.Uplift of the Variscan Massifs and development of ECRIS exerted strong controls on the Neogene evolution of drainage systems in the Alpine foreland.  相似文献   

现今绝对板块运动   总被引：1，自引：0，他引：1  

魏子卿 《地球科学与环境学报》2009,31(4):331-343

根据热点假设,热点对于中间层是固定的.相对热点的板块运动叫做绝对板块运动.绝对板块运动模型可以通过反演火山链传播的速率和走向数据以确定相对板块运动在角速度空间的原点来得到.利用一组近来(0～7.8 Ma)全球分布的热点的迁移速率和走向数据,结合板块运动模型NNR-NUVEL1A,已研制出一个叫做APM2的现今绝对板块运动模型.按照该模型,太平洋板块围绕60.063°S、102.210°E处的极以(0.833 0°±0.013 3°)/Ma的速率运动,非洲板块围绕46.849°N、44.372°W的极以(0.101 5°±0.013 4°)/Ma的速率运动,南极板块的运动则以46.871°N、146.942°E为极,速率为(0.084 6°±0.017 7°)/Ma,欧亚板块的运动更慢,极为27.291°N、171.925°W,速率为(0.065 5°±0.020 6°)/Ma.这一模型表明,岩石圈相对深部地幔有一个以49.423°S、90.625°E为极,速率为(0.198 3°±0.013 5°)/Ma的净旋转.表明太平洋热点同印度-大西洋热点不一致,显示太平洋热点的运动也不一致.为了分析和比较,还给出了仅用全球分布的热点的走向数据和仅用印度-大西洋热点的走向数据得到的板块绝对运动的角速度.  相似文献   

Autochthonous block fields in southern Norway: Implications for the geometry,thickness, and isostatic loading of the Late Weichselian Scandinavian ice sheet     

Atle Nesje  Svein Olaf Dahl 《第四纪科学杂志》1990,5(3):225-234

The consistent geographical and altitudinal distribution of autochthonous block fields (mantle of bedrock weathered in situ) and trimlines in southern Norway suggests a multi-domed and asymmetric Late Weichselian ice sheet. Low-gradient ice-sheet profiles in the southern Baltic region, in the North Sea, and along the outer fjord areas of southern Norway, are best explained by movement of ice on a bed of deforming sediment, although water lubricated sliding or a combination of the two, may not be excluded. The ice-thickness distribution of the Late Weichselian Scandinavian ice sheet is not in correspondence with the modern uplift pattern of Fennoscandia. Early Holocene crustal rebound was apparently determined by an exponential, glacio-isostatic rise. Later, however, crustal movements appear to have been dominated by large-scale tectonic uplift of the Fennoscandian Shield, centred on the Gulf of Bothnia, the region of maximum lithosphere thickness.  相似文献   

南海东北陆缘的地壳速度结构及其构造意义: 来自广角地震剖面的约束     

赵俐红  刘欣悦  支鹏遥  刘晨光  李官保  郑彦鹏  贺恩远  王星月 《地质学报》2023,97(6):1766-1779

南海东北部深部地壳结构蕴含着南海陆缘伸展张裂过程的重要信息。在南海东北陆缘布设的一条广角地震测线(DP13)沿NW-SE方向依次穿过东沙隆起和台西南盆地。本文利用射线追踪和正演走时拟合软件RayInvr构建地壳纵波速度结构,模型表明：沉积层速度1.6～4.6 km/s,厚度0.5～3.8 km,横向分布不均匀,沉积基底起伏剧烈;莫霍面埋藏深度由陆架区的25.5 km急剧减小到陆坡下方的13 km,随后向下陆坡远端增深至16 km;陆架处东沙隆起下方地壳厚度从～25 km减薄到～21 km,下陆坡远端地壳厚约10～13 km,地壳拉张因子分别为1.3～1.5和2.6～3.1,表现为轻微和中等减薄;陆坡区台西南盆地内地壳厚度从17 km急剧减薄至7～8 km,地壳拉张因子高达4.6,呈超伸展减薄;地壳厚度由陆向海非单调减薄,地壳伸展具有明显的空间差异性;陆架-上陆坡和下陆坡下地壳底部发现两个相对孤立的不连续高速体,速度分别为7.0～7.5 km/s和7.0～7.3 km/s,厚度分别3～5 km和1～3 km,前者位于古太平洋俯冲带前缘,几乎与南海东北部高磁异常重叠,推测由中生代古太平洋板...  相似文献   

Data selection using support vector regression     

Michael B.RICHMAN  Lance M.LESLIE  Theodore B.TRAFALIS  Hicham MANSOURI 《大气科学进展》2015,32(3):277-286

Geophysical data sets are growing at an ever-increasing rate, requiring computationally efficient data selection(thinning)methods to preserve essential information. Satellites, such as Wind Sat, provide large data sets for assessing the accuracy and computational efficiency of data selection techniques. A new data thinning technique, based on support vector regression(SVR), is developed and tested. To manage large on-line satellite data streams, observations from Wind Sat are formed into subsets by Voronoi tessellation and then each is thinned by SVR(TSVR). Three experiments are performed. The first confirms the viability of TSVR for a relatively small sample, comparing it to several commonly used data thinning methods(random selection, averaging and Barnes filtering), producing a 10% thinning rate(90% data reduction), low mean absolute errors(MAE) and large correlations with the original data. A second experiment, using a larger dataset, shows TSVR retrievals with MAE < 1 m s-1and correlations 0.98. TSVR was an order of magnitude faster than the commonly used thinning methods. A third experiment applies a two-stage pipeline to TSVR, to accommodate online data. The pipeline subsets reconstruct the wind field with the same accuracy as the second experiment, is an order of magnitude faster than the nonpipeline TSVR. Therefore, pipeline TSVR is two orders of magnitude faster than commonly used thinning methods that ingest the entire data set. This study demonstrates that TSVR pipeline thinning is an accurate and computationally efficient alternative to commonly used data selection techniques.  相似文献   

中国大陆岩石圈导电性结构研究——大陆电磁参数“标准网”实验（SinoProbe-01）   总被引：6，自引：0，他引：6  

魏文博  金胜  叶高峰  邓明  景建恩  李艳军  张乐天  董浩  张帆  谢成良 《地质学报》2010,84(6):788-800

"中国大陆地壳探测计划"的首要目标是岩石圈物性结构、构造和物质组成的探测,这包括大陆岩石圈的地震波速度、密度、磁性、导电性和放射性结构研究。其中,大陆岩石圈导电性结构的研究越来越引起人们的重视。利用岩石圈导电性结构模型不仅可以推断地球内部的岩、矿石组成和地质构造轮廓,还可以间接提供有关地球内部热结构的信息,为研究地球内部物质状态、地壳运动过程及其动力学机制等科学命题服务。因此,很多发达国家自上世纪70年代以来,陆续启动了岩石圈导电性结构探测。2004年,美国开始了"地球透镜计划(EarthScope)";其中,"大地电磁阵列"(USArray)是整个计划中的重要部分,是一个大陆尺度的大地电磁场观测计划,它将为北美大陆的构造与演化提供新的约束。在中国,大陆岩石圈导电性结构研究虽取得一系列重要成果,但也仅限于对其基本格局有一定认识,远远满足不了大陆动力学问题研究的需要。为了研究中国大陆形成、演化机理,首先需要确定中国大陆岩石圈三维构造模型、热结构和流变性特征,而这一切都与更详细、更准确的中国大陆岩石圈导电性结构有着密切关系。为了实现构建中国大陆岩石圈电磁学参数三维数据体及导电性结构标准模型的目标,"深部探测技术与实验研究专项"设立"大陆电磁参数标准网实验研究(SinoProbe-01)"项目,解决大陆尺度、阵列式(Array)大地电磁场(MT)标准网观测计划的关键技术问题,研究具体的实施方法技术,并提供示范性成果。项目将尽可能预先建立覆盖全国、网度为4°×4°的阵列式区域大地电磁参数标准网控制格架,并以华北和青藏为基地创立阵列式区域大地电磁场"标准点"1°×1°观测网的构建方法、技术;构建华北和青藏地区壳、幔电磁参数三维结构标准模型"格架",以及不同网度的壳、幔物性三维结构模型,为覆盖全国的阵列式区域大地电磁"标准点"观测网最佳网度选择提供依据,为最终建立中国大陆岩石圈三维导电性结构标准模型奠定基础,为预测我国超大型金属成矿远景区提供方向。完成本项目研究将对揭示中国大地构造特点和岩石圈结构提供重要依据,对油气及固体矿产资源远景评估提供制约,并对完善后板块大地构造理论有重要意义。开展这方面的研究将揭开中国大地构造地球物理学新阶段的序幕,为中国可持续发展与地球科学的进步作出贡献。  相似文献   

安徽庐枞火山岩盆地橄榄玄粗岩系的地球化学特征及其对下扬子地区晚中生代岩石圈减薄机制的约束   总被引：17，自引：2，他引：15  

薛怀民  董树文  马芳 《地质学报》2010,84(5):664-681

庐枞盆地内的中生代火山-潜火山岩具高钾和相对富碱为特性,属典型的橄榄玄粗岩系列。它们在地球化学上表现出明显富集Rb、Th、U、K等强不相容元素和轻稀土元素,亏损高场强元素Nb和Ta的特征。Nd、Sr同位素组成总体位于富集型的扬子克拉通岩石圈地幔的范围内或其附近,显示其母岩浆主要是由富集型地幔部分熔融形成的。火山-潜火山岩的成分变异趋势显示橄榄玄粗质幔源岩浆在高压下(斜长石稳定压力之下,1.5GPa)经历过以单斜辉石和钛铁氧化物为主的矿物分离结晶作用。低压下矿物的分离结晶作用及上地壳物质的混染则不明显。这套火山-潜火山岩的部分地球化学性质(如Ce/Yb比值)类似于大洋岛弧内的橄榄玄粗岩,可能意味着区内由于岩石圈的减薄,软流圈地幔上涌到了岩石圈相对较浅的部位,控制源区部分熔融的主要是尖晶石相地幔岩。虽然局部(如靠近郯庐断裂的盆地西缘)可能存在着明显的热侵蚀,但"突发性的"机械拆沉是区内(乃至整个长江中下游地区)岩石圈减薄的主要机制。在整个晚中生代岩石圈减薄的过程中,这两种机制可能一直相互促进着。  相似文献   

河南舞阳南部张士英岩体的地球化学与成因及其构造意义   总被引：4，自引：3，他引：1  

李创举  包志伟 《大地构造与成矿学》2010,34(3)

张士英岩体岩石类型以石英二长岩、石英正长岩为主。岩体属于准铝质的高钾-钾玄岩系列(Al2O3为14.8%～16.7%,A/CNK=0.77～1.02,K2O/Na2O在1.00～1.43之间),稀土元素总量在261.7～381.0μg/g之间,轻稀土元素相对富集,稀土元素球粒陨石标准化模式呈右倾平滑曲线,(La/Yb)N比值为28～50,具有轻微的Eu负异常,Eu/Eu?比值在0.73～0.87之间。微量元素组成上表现为Sr、Ba、Nb、Ta的亏损,而Th、U相对富集。(87Sr/86Sr)i初始平均值为0.709,εNd(t)值为-13.9～-19.9,Nd的模式年龄为1.48～2.10Ga。岩体锆石LA-ICP-MSU-Pb年龄为(124.2±0.5)Ma,为早白垩世岩浆作用的产物。岩体侵位的区域地质背景为华北克拉通白垩纪大规模岩石圈转型和减薄时期,岩石的微量元素及同位素特征表明,岩体主要来源于下地壳物质的部分熔融,但有年轻地幔物质的加入。反映在区域强烈伸展拉张和岩石圈减薄背景下,软流圈地幔岩浆底侵所造成的下地壳部分熔融及壳幔混合过程。  相似文献