New data on the structure of the sedimentary section on the Ita Mai Tai Guyot (Magellan Seamounts,Pacific Ocean)

The geological-prospecting investigations carried out by scientists from the Yuzhmorgeologiya State Scientific Center in the eastern segment of the Magellan Seamounts of the Pacific during the cruise of the R/V Gelendzhik in 2003–2010 brought new data on the topography of the Ita Mai Tai Guyot and its Lower Cretaceous-Pleistocene sedimentary section. The guyot is characterized by its complex irregular morphology with angular outlines being complicated by numerous relief mesoforms: spurs, scarps, and volcanic cones and domes. It is shown that the sedimentary cover was formed during a long period. The analysis of the organic macro- and microfaunal remains from the sedimentary rocks made it possible to define transgressive phases in the guyot’s development: the Albian-Cenomanian, the Late Campanian-Maastrichtian, and the late Paleocene-early Eocene. The oolitic limestone sequence recovered by DSDP Hole 202 is determined to be the Albian in age. Based on the original and published data, the geological development of the guyot was analyzed in comparison with other similar structures of the Magellan Seamounts.     

The first finds of cretaceous belemnites from the Magellan Rise, Pacific Ocean

The occurrence of belemnites in Mesozoic sediments of the Pacific guyots is established for the first time (rostra Dimitobelidae gen. et sp. indet. from the late Campanian-Maastrichtian detrital limestone of the DVGI Guyot, Belemnitella? sp. from oolitic limestone of the Gelendzhik Guyot, which are presumably of the Santonian-Maastrichtian age, and Belemnitidae? gen. et sp. indet. from the Maastrichtian oolitic limestone of the Butakov Guyot, the Magellan Rise). In recent years, fossil cephalopods important in stratigraphic and paleobiogeographic aspects have been found at five guyots of that rise. New data on fossil invertebrates from the study region suggest breaks in the sedimentation here at the terminal Maastrichtian, Paleogene, and initial Neogene time. Possible limits of vertical migration in the tropical Pacific are estimated for the Late Cretaceous belemnites based on preliminary results of the oxygen isotope analysis.     

Structural features of the northeastern slope of Govorov Guyot,Magellan Seamounts,Pacific Ocean

Photo/TV surveying (approximately 4500 photographs of the oceanic floor) and multibeam echo sounding data were compared to analyze the structural features of the northeastern slope of Govorov Guyot. A network of linear structures complicating this slope was visualized. The trajectories of the linear structures were determined and shown in rose diagrams. It was demonstrated that the photo/TV surveying of the oceanic floor represents an effective tool for studying its topography. The blocks bordered by linear fractures are characterized by different parameters of ferromanganese ore mineralization of the crust type, which may be explained by the determining role of the tectonic factor in the relief-forming process. The combination of the topographic features and the hydrodynamic regime within the blocks provides conditions favorable to different extents for the accumulation of Mn hydroxides.     

New geological and paleontological data on Alba Guyot (Magellan Seamounts, Pacific Ocean)

New materials obtained in the Pacific during cruises of the R/V Gelendzhik carried out by the State Scientific Center Yuzhmorgeologiya in 2000–2001 make it possible to specify the geologic and geomorphologic structure of Alba Guyot and clarify lithological and paleontological characteristics of lithotectonic rock complexes ranging from the Early Cretaceous to Pleistocene in age. Based on macro-and microfossils from sedimentary rocks several “transgressive” phases are distinguished in the guyot development: Cenomanian-Turonian, late Campanian-Maastrichtian, late Paleocene-middle Eocene, and Late Cenozoic. Finds of Paleogene molluscan and coral remains, together with planktonic foraminifers, imply relatively shallow sedimentation settings on Alba Guyot during the early Paleocene.     

New data on the morphology and geological structure of the Gramberg Guyot (Magellan Seamounts, Pacific Ocean)

The geological-geophysical studies carried out in the western part of the Pacific Ocean by the State Research Center “Yuzhmorgeologiya“ during cruises of the R/V “Gelendzhik” in 2002–2004 yielded new data on the relief of the Gramberg Guyot and its constituting rocks, which appeared to be Early Cretaceous to Pleistocene in age. The analysis of macro- and microfaunal remains in sedimentary rocks made it possible to define the transgressive phases in the development of seamounts (the Cenomanian-Turonian, Late Campanian-Maastrichtian, and Late Cenozoic). The geological development of the Gramberg Guyot is compared with that of other similar structures of the Magellan Seamounts.     

Conditions of basalt formation in the Dzhida zone of the Paleoasian Ocean

Petrological and geochemical studies performed with invoking data on the compositions of clinopyroxenes have clarified the conditions of formation of Vendian-Cambrian basaltic complexes in the Dzhida zone of the Paleoasian Ocean (northern Mongolia and southwestern Transbaikalia). The research was based on a comparative analysis with reference igneous basaltic associations. Of special importance are our microprobe data on trace and rare-earth elements in clinopyroxenes from igneous rocks of different present-day geodynamic settings, namely, N-MORB (Mid-Atlantic Ridge, Central Atlantic), OIB (Bouvet Island, South Atlantic), WPB (within-plate tholeiitic plateau basalts of the Siberian Platform), and boninites of ensimatic arcs (Izu-Bonin island arc, Pacific). The studies have shown that the paleo-oceanic structures in the district of the Urgol guyot formed during geodynamic processes under the impact of mantle plumes on oceanic spreading crust, which resulted in oceanic basaltic plateaus and within-plate oceanic islands. All these structures were later superposed by typical island-arc structure-lithologic associations. Formation of basalt complexes in the Dzhidot guyot district proceeded with a stronger effect of enriched plume melts of within-plate oceanic islands as compared with the Urgol guyot. This is evidenced from petrochemical and geochemical data showing the development of OIB-type magmatic systems on the oceanic basement. Data on clinopyroxenes confirm the participation of mantle plume in this process, which led to the evolution of magmas from typical oceanic basalts (MORB) to plateau basalts and OIB.     

麦哲伦戈沃罗夫盖特平顶海山钴结壳资源评价

为能科学、快速量化地圈定出大洋海山钴结壳优质矿区,笔者基于国际海底管理局提出的矿区选取模型,利用我国西太平洋海山钴结壳资源调查的公开的拖网采样资料,综合钴结壳的分布规律和证据权法所得海山钴结壳资源预测后验概率图,将西太平洋麦哲伦海山区戈沃罗夫盖特平顶海山圈定为钴结壳资源前景较好的远景区,并采用人机交互式的矿区圈定方法圈定出符合国际海底管理局规章要求的7个群组共100个钴结壳矿块。据此估算出戈沃罗夫盖特平顶海山湿结壳资源量为69 487.6×10⁴ t;圈定的100个矿块主要分布在2 000~3 000 m斜坡上,湿结壳资源量为14 092×10⁴ t,干结壳资源量为9 789.35×10⁴ t;锰金属量为1 961.3×10⁴ t,铜金属量为10.17×10⁴ t,钴金属量为54.06×10⁴ t,镍金属量为34.87×10⁴ t。这些数据表明,戈沃罗夫盖特平顶海山规模较大,钴结壳资源前景潜力大,可作为钴结壳深入调查和矿区申请备选海山。     

维嘉海山沉积过程及其对西太平洋海山演化的意义

海山沉积过程与全球气候变化和古海洋演化有着紧密联系,维嘉海山保留了西太平洋晚中生代以来的完整沉积记录,是探索西太平洋海山构造演化的理想场所.基于浅地层剖面、大洋钻探和最新相关研究成果,通过研究海山的沉积特征、火山活动和沉降速率等,探索西太平洋维嘉海山晚中生代以来的沉积过程.结果显示维嘉海山顶部发育3个沉积单元,并发现了...     

西太平洋海域海山地形分形特征研究

对太平洋麦哲伦海山区、威克—马尔库斯海山区、马绍尔群岛、中太平洋海山区及莱恩群岛5个海山区的平顶海山与尖顶海山地形进行分形研究,结果表明两种类型海山地形具有不同的分形特征。海山形态投影覆盖法揭示平顶海山具有单分形的大尺度构造分形,尖顶海山具有大尺度构造分形和小尺度结构分形的双分形结构。海山等高线尺度法分形结果显示,同一海山区平顶海山分维值小于尖顶海山的;同一海山不同高程段等高线分维值基本保持稳定,垂向上具有明显的分段性,可以参考并使用它进行地貌垂向分带。     

西太平洋维嘉平顶山沉积特征及富钴结壳资源意义

基于中国大洋36和41航次浅地层剖面数据,结合DSDP钻井及国内外相关研究,对西太平洋维嘉平顶山顶部沉积物的浅地层剖面特征、沉积环境、沉积时代、沉积物厚度分布特征等进行了研究,发现3种主要的地层反射特征,分别代表3个沉积单元;山顶沉积物的厚度分布呈现出3个沉积中心区和4个基岩裸露/沉积物稀薄区的特点;平顶山东部的沉积异常可能与始新世的第二次火山活动有关。根据富钴结壳的生长和发育特点,结合维嘉平顶山的沉积物分布特征,圈定了结壳资源潜力分布区。维嘉平顶山作为中国重要的富钴结壳合同区块,本次研究对其富钴结壳资源进一步的勘探工作具有指导意义。     

An Effective Method to Determine the Distribution Boundary of Cobalt-Rich Fe-Mn Crusts on a Guyot： Synchronous Application of Sub-bottom Profiling and Deep-Sea Video Recording

Cobalt richferromanganesecrust,hereaftercalled Fe Mncrust,isoneoftheimportantmarinemineralre sourcesintheinternationalseabed.Fe Mncrustoccurs onthesurfaceofseamounts,whichareenrichedinco balt,nickel,copper,platinumgroupelements,rare earthelementsandothe…     

Geochemical zoning in ferromanganese crusts of Ita-MaiTai guyot

Samples of ferromanganese crusts dredged from Ita-MaiTai guyot (Magellan seamounts, Pacific Ocean) were studied. They are made up of a complete stratigraphic section of different-age layers, including unique oldest relict layers in some samples. The study of trace, rare-earth, and noble element (including Pt and Pd) distribution showed that old layers differ from young ones in terms of Co, TR, S, As, and P. In addition, composition of the crusts significantly varies depending on the spatial position of sample in the guyot. In some zones, crusts enriched in trace elements were generated both in the Pleistocene and Paleogene. Significant variations established in trace element composition of different-age layers indicate that trace element composition of the crusts notably evolved with time, which could be caused by productivity of biocenosis or change in the formation depth of crusts on the guyot due to vertical tectonic movements.     

基于多尺度数字地形定量分析的月球线性构造自动提取研究

月球表面构造对于理解和重建月球地质构造演化具有重要意义,月岭、月溪等线性构造的形态及分布特征与月球内动力构造运动密切相关。极为有限的样品和难度极高的野外勘察使得遥感成为行星科学研究的最主要手段。中国、美国、日本、印度等国先后发射的多颗新型探月卫星获取了大量高质量数据,尤其是高分辨率的数字地形数据(DTM,Digital Terrain Model)。高分辨率的DTM为月球表面构造特征的自动提取带来了新的机遇与挑战。文中利用多种分辨率的DTM数据,基于多尺度数字地形定量分析方法,识别和提取月球表面的线性构造。使用的地形数据包括500 m分辨率“嫦娥一号”激光高度计数据,100 m分辨率LRO-WAC广角相机数据,60 m分辨率的LRO-LOLA激光测距仪数据以及分辨率高达5 m的LRO-NAC窄视角相机数据。文中使用地形曲率来识别月溪月岭等线性构造,并利用不同滑动窗口大小和阈值进行线性构造的自动提取。对研究区试验结果的定量分析表明,文中提出的基于地形曲率的月表线性构造自动提取方法是有效且可行的,其结果可为月球表面线性构造解译提供重要参考,提高构造解译时效性和精度。     

Ore Content of Cobalt-Rich Ferromanganese Crusts of the Govorov Guyot of the Magellanic Mountains of the Pacific Ocean

Doklady Earth Sciences - The main ore minerals of all layers of cobalt-rich ferromanganese crusts of Guyot Govorov of the Magellanic Mountains of the Pacific Ocean are poorly crystallized, poorly...     

西准噶尔地区多源遥感信息的线性构造提取与定量分析

夹持在近东西向额尔齐斯断裂和天山走滑断裂系统之间的西准噶尔地区,经历了自晚古生代晚期以来长期复杂的陆内构造变形历史。线性构造的长度、方向以及空间分布能够反映构造变形的强度和样式,指示应力作用的方式。本文选取新疆西准噶尔地区为研究区,利用ASTER、Landsat等多源遥感数据通过彩色合成、主成分分析、波段比值和Sobel滤波等增强显示断裂构造在遥感影像上的空间分布和光谱信息,并利用Canny边缘检测与人工解译相结合的方法提取研究区内线性构造;运用地质统计学的原理和方法对提取出的线性构造进行定量分析。结果表明,研究区内依长度优选方位确定的主断裂走向为N50°～60°E,代表了区域一级构造即达拉布特断裂展布的方位;依线性构造数量优选方位确定的次级断裂走向为80°～90°(近东西向),代表了区域三级构造的方位;介于以上两者之间的线性构造,即数量与长度均适中的线性构造,代表了区域二级构造的方位。线性构造的区域分布,揭示了在南北向主压应力作用下,西准噶尔地区构造体系的组成与构造变形特征。由此说明,多源遥感信息提取的线性构造定量分析,对于区域断裂构造体系的厘定具有重要意义。     

西昆仑山前冲断系的结构特征

西昆仑山前为一薄皮冲断构造系 ,按冲断系不同区段结构和变形样式的差异 ,由北而南可以将西昆仑冲断系分为以薄皮变形为主的北带和以厚皮变形为主的南带。北带进一步划分为 :帕米尔北缘弧形构造带、齐姆根构造带、柯克亚—桑株构造带和皮山—和田构造带 4个次一级构造带。其中 ,帕米尔北缘弧形构造带为显露型近东西走向展布的紧密的线性冲断褶皱带和断裂带 ;齐姆根构造带为受走滑与冲断作用复合影响的隐伏型盲冲走滑构造带 ;柯克亚—桑株构造带是以冲断作用为主的隐伏型盲冲构造带 ;皮山—和田构造带则是典型的显露型冲断推覆体。构造带的走向差异、边界条件的不同和空间上的制约是各构造带之间差异活动的原因。在每一个构造线变化的区段与邻近部位具有不同的结构 ,从而在空间上形成了较为复杂的冲断体系。     

Lithological and structural prerequisites for localization of ore deposits in the Mesoproterozoic-Neoproterozoic Uchur-Maya depression (Siberian Platform)

A set of sketch maps has been compiled including a structural map for the Uchur-Maya depression, maps of the fractures based on the data derived from the digital elevation model processed using the modulus of the topographic gradient for discriminating the fault boundaries, and maps of the lineament distribution and the density of the elementary linear structures. On these sketch maps, the location of the ore deposits and the occurrences of various metals are plotted within the bounds of the Uchur-Maya depression with the defining structural and lithological factors that control the ore occurrences. The locations of the ore objects relative to the differently oriented faults and the lineament network based on the data of the digital elevation model’s processing and the density of the linear structures have been analyzed. The most important lithological factors that control the ore deposits are the pre-Mesoproterozoic structural-stratigraphic unconformity zones, the contact zones between the Mesoproterozoic formations with their contrasting physical and chemical properties, and the high-porosity (cavernous) dolomite member in the Yudomian Group of the Vendian.     

新疆哈拉奇地区遥感信息提取与解释

以ETM＋图像数据为信息源,运用比值变换和主成分分析技术,进行数据融合和图像增强处理,结合数字高程模型,提取新疆哈拉奇地区构造和近矿围岩蚀变信息。根据线性构造的影像特征分析,划分出3个构造组合：区域性近东西向、北东向、北西向构造。同时利用分形理论的求和法进行了研究区遥感蚀变异常的提取,并将蚀变结果与构造和化探异常区进行了对比分析。     

Assessment of acoustic backscatter intensity surveying on deep-sea ferromanganese crust: Constraints from Weijia Guyot,western Pacific Ocean

Near-bottom observation data from the manned deep submersible Jiaolong with high-precision underwater positioning data from Weijia Guyot, Magellan Seamounts in the Western Pacific Ocean are reported. Three substrate types were identified: Sediment, ferromanganese crust, and ferromanganese crust with a thin cover of sediment. The ferromanganese crusts show clear zoning and their continuity is usually disturbed by sediments on areas of the mountainside with relatively gentle slope gradients. The identified substrate spatial distributions correspond to acoustic backscatter intensity data, with regions of high intensity always including crust development and regions of low intensity always having sediment. Therefore, acoustic backscatter intensity surveying appears useful in the delineation and evaluation of crust resources, although further more work is needed to develop a practicable methodology.     

重磁异常的小波模极大值分解及其在北衙矿区中的应用

位场数据异常存在的线性特征往往对应着地下断裂构造、不同岩性地质体的边界接触带或者其他具有一定密度或磁性差异的构造特征。对这些线性特征进行增强、提取并进行半定量地解释是重磁资料处理的主要内容。然而,位场数据中若混入噪声干扰,再利用总水平导数、总水平梯度倾斜角等方法进行高次求导运算会把噪声放大,导致提取的线性构造位置发生偏离甚至出现错误。为了获取较为准确的线性构造及边界位置,选取对噪声干扰不敏感的小波模极大值方法,将该方法用于模型试验和实际矿区数据处理中,都能较好地定位出异常体模型边界和矿体的投影边界,表明小波模极大值是一种有效的重磁异常线性特征增强与提取方法。