干旱地貌学研究进展

世界上许多沙漠在更新世确实急剧地扩大了(Goudie, 1981; Street,1981)。对于沙漠形成的时代,有了日益增多的证据,尤其是从深海结核沉积中得到的材料。远离西撒哈拉的沉积结核中还含有可以检定的风成物质,表明在约二千万年以前(早中新世)北非就存在着一个发育良好的干旱区(Diester-Haass and Schrader, 1979)。同样,斯埃瑟(Siesser, 1981)证明在晚中新世波恩古尔勒海流(Bengular Current)的寒冷上升流(upwelling water)造成了沿西南非洲(纳米比亚)纳米布海岸的干旱化。对北太平     

苏联社会经济地理学的任务

最近十年来,做为一门科学的地理学已经发生了重大的变化。现在,社会经济地理学形成了一种关于社会空间形式的知识体系。经济一地理这门学科的分化同时又是综合的趋向是和地理学研究当前强调与经济学、生态学与社会学方面的联系有关的。     

电阻率测深量板的快速计算法

水平地层电阻率测深量板广泛用来快速推断解释电测深曲线.现有构制量板的方法都是利用合适的求积法对斯忒藩斯库积分求数值解.随着快速数字计算机的发展,这种方法获得了更大的成效.最近戈什利用线性滤波方法研究成一种迥然不同的计算电阻率测深量板的方法.本文介绍一种基于斯忒藩斯库方程,计算施伦贝尔热和温纳电极排列的水平层状地层测深量板的快速方法.在斯忒藩斯库方程中有贝塞尔函数,由于J_j(x)收敛慢,而且具有振     

费尼克斯铜矿的资源勘探和品位控制

历史情况葛兰拜矿山公司的费尼克斯铜矿位于加拿大不列颠哥伦比亚省南部格兰德·福克斯镇与戈瑞恩坞镇之间.矿区的开采权在1891年就已用标椿作志.从那时起,曾经做过各种评价和勘探工作,但是直到1899年矿山和冶炼厂开始兴建的时候,矿区的储量还没有掌握.连结矿区和恪兰德·福克斯冶炼厂的铁路在1900年建成后,即开始运出矿石.此后,生产延续了19年.矿山初期的产量为每日63O吨,以后曾经发展到3000吨以上.当时,格兰德·福克斯冶炼厂曾经是英国最大的冶炼厂之一,在19年中,矿石的总产量为1370万吨,品位:铜1.2%,金O.04盎斯/吨,     

Fluid-driven Hydrovolcanic Activity along Fracture Zones and near Seamounts: Evidence from Deep-sea Fe-rich Spherules,Central Indian Ocean Basin

An insight on occurrence of Fe-rich spherules from the Central Indian Ocean Basin (CIOB) provides an understanding of their distribution at a water depth of >5,000 m. In the present study, Fe-rich spherules are identified to occur in two different sediment types (i.e., siliceous and pelagic) and tectonic settings (i.e. near seamounts and fracture zones). These are single spheres or aggregates, of different sizes (63 to 390 μm) and show textural variability (smooth/quenched, brickwork, corkscrew, interlocking and dendritic). A comparative study based on physical morphology and chemical composition suggests a common mechanism of formation. The association of spherules with fracture zones (FZ) and seamounts signifies that morpho-tectonic features play an important role in fluid-driven hydrovolcanism. Based on the evidence and geologic conditions existing in the basin, we conclude that molten fuel-coolant interaction (MFCI) coupled with submarine hydrothermal exhalations could be an ideal mechanism for the formation of spherules and Fe-particles. The accretion of the spherules on the surface sediments could be a result of recent volcanic phenomena, while those occurring at different depths (280–355, and 460–475 cm-bsf) within the sediment core indicate two different episodes. The study provides a global implication in understanding fluid-driven magmatism in a deep-sea intraplate environment.     

Neoproterozoic U-Th-REE-bearing Pegmatites in Wadi Ibib,South Eastern Desert,Egypt:Structural and Geochemical Measures for a Syn-Tectonic Anatectic Model of Formation

The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone (HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N-trending pegmatite dikes. Whole-rock geochemistry of the pegmatites reveals a peraluminous (S-type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N-trending tectonic fabrics, such as axial planar foliation and dextral-shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space-localized decompression-induced partial melting of peraluminous garnet-bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage (D3) in the evolution of the south Eastern Desert terrane, due to end-orogeny system pressure-release.     

非恒定流驱动下床面形态变化特征

为深入认识非恒定流驱动下床面形态的演变规律及尺度变化趋势,采用水泵控制系统生成了一系列历时与洪峰流量不同的洪水过程来冲刷由粗沙组成的实验动床（中值粒径d₅₀=1.95 mm）,研究中运用非恒定流的形态、非恒定性及水流做功参数来量化洪水过程;统计分析河床高程数据得到床面形态的波长、波高及陡度。实验结果表明:在不同尺度的非恒定流洪水作用下,实验动床表面分别形成了沙垄、交错边滩以及介于两者之间的过渡型床面形态;洪水的非恒定性对床面形态尺度的影响最大,其次是水流做功参数,而非恒定流的形态影响较为微弱;在此基础上构建了用于描述非恒定流驱动条件与床面形态尺度响应的定量关系。     

Textural and geochemical characteristics of late Pleistocene to Holocene fine-grained deep-sea sediment cores(GM6 and GM7),recovered from southwestern Gulf of Mexico

Texture, mineralogy, geochemistry, and ~(14)C ages of two deep-sea sediment cores(GM6 and GM7) recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The sediments are enriched in fine-grained silt and clay and poor in sand content. Mineralogically, the sediments consist of quartz,calcite, smectite, and kaolinite. Based on the ~(14)C data, the age of the GM6 and GM7 sediment cores were calculated as23,615 cal yrs. BP and 19,007 cal yrs. BP, respectively. The weathering indices such as chemical index of alteration(CIA),chemical index of weathering(CIW), and plagioclase index of alteration(PIA) in GM6(56-69, 60-74, and 61-73,respectively) and GM7(54-69, 57-76, and 55-74, respectively) cores revealed a moderate-to-high intensity of weathering. The rare earth element(REE) patterns suggested that the sediments were derived mostly by the weathering of intermediate rocks, exposed along the coastal regions of the Gulf of Mexico. The trace elemental ratios like V/Cr(2),Ni/Co(2), and Cu/Zn(1), authigenic uranium content(1), and Ce anomaly(Ce/Ce~* ≤ 1) suggested that the sediments were deposited under an oxic condition, which was also revealed by the benthic foraminiferal assemblages throughout the GM6 and GM7 sediment cores.     

日本东北潜在大地震的规模曾被低估

自20世纪70年代以来,科学家已经把地球分为可以产生9.0级地震的板块边界和不会产生9.0级地震的板块边界.然而,2011年发生在日本东北的大地震与2004年发生在苏门答腊—安达曼的超级大地震却让科学家们震惊,因为这两个地区被认为都不可能发生震级超过8.4的大型逆冲地震.现在,地震科学家经重新研究后都承认现有的最大地震规模的预测模型不再有效.人们对这些模型已经提出疑问:苏门达腊什么时候驱动一个板块边界穿过它们的中心?日本东北又在何时驱动了另一个板块边界?     

Serpentinized Peridotites at the North Part of the Wadi Allaqi District (Egypt): Implications for the Tectono-Magmatic Evolution of Fore-arc Crust

The Neoproterozoic Allaqi-Heiani suture （800-700 Ma） in the south Eastern Desert of Egypt is the northernmost linear ophiolitic belt that defines an arc-arc suture in the Arabian- Nubian shield （ANS）. The Neoproterozoic serpentinized peridotites represent a distinct lithology of dismembered ophiolites along the Allaqi-Heiani suture zone. The alteration of peridotites varies, some contain relicts of primary minerals （Cr-spinel and olivine） and others are extremely altered, especially along thrusts and shear zones, with development of talc, talc-carbonate and quartz-carbonate. The fresh cores of the chromian spinels are rimmed by ferritchromite and Cr- magnetite. The fresh chromian spinels have high Cr# （0.62 to 0.79）, while Mg# shows wider variation （0.35-0.59）. High Cr# in the relict chromian spinels and Fo content in the primary olivines indicate that they are residual peridotites after extensive partial melting. The studied ophiolitic upper mantle peridotites are highly depleted and most probably underwent high degrees of partial melting at a supra-subduction zone setting. They can be produced by up to -20%-22% dynamic melting of a primitive mantle source. The mineralogical and geochemical features of the studied rocks reflect that the mantle peridotites of the north part of the Wadi Allaqi district are similar to the fore-arc peridotites of a supra-subduction zone.