Petrological and Os Isotopic Characteristics of Zedong Peridotites in the Eastern Yarlung–Zangbo Suture in Tibet

The Zedong ophiolites in the eastern Yarlung–Zangbo suture zone of Tibet represent a mantle slice of more than 45 km~2. This massif consists mainly of mantle peridotites, with lesser gabbros, diabases and volcanic rocks. The mantle peridotites are mostly harzburgite, lherzolite; a few dike-like bodies of dunite are also present. Mineral structures show that the peridotites experienced plastic deformation and partial melting. Olivine(Fo89.7–91.2), orthopyroxene(En_(88–92)), clinopyroxene(En_(45–49) Wo_(47–51) Fs_(2–4)) and spinel [Mg~#=100×Mg/(Mg+Fe)]=49.1–70.7; Cr~#=(100×Cr/(Cr+Al)=18.8–76.5] are the major minerals. The degree of partial melting of mantle peridotites is 10%–40%, indicating that the Zedong mantle peridotites may experience a multi–stage process. The peridotites are characterized by depleted major element compositions and low REE content(0.08–0.62 ppm). Their "spoon–shaped" primitive–mantle normalized REE patterns with(La/Sm)_N being 0.50–6.00 indicate that the Zedong ultramafic rocks belong to depleted residual mantle rocks. The PGE content of Zedong peridotites(18.19–50.74 ppb) is similar with primary mantle with Pd/Ir being 0.54–0.60 and Pt/Pd being 1.09–1.66. The Zedong peridotites have variable, unradiogenic Os isotopic compositions with ~(187)Os/~(188)Os=0.1228 to 0.1282. A corollary to this interpretation is that the convecting upper mantle is heterogeneous in Os isotopes. All data of the Zedong peridotites suggest that they formed originally at a mid-ocean ridge(MOR) and were later modified in supra–subduction zone(SSZ) environment.     

Strengthening mechanisms in cement-stabilized kaolinite revealed by cross-scale nanoindentation

Acta Geotechnica - The macroscale mechanical properties of cement-stabilized soil have been widely reported, but the microscale behavior remains largely unexplored. This paper presents the first...     

Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems

Listwanite from the Luobusa ophiolite,Tibet,forms a narrow,discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. Three alteration zones characterized by distinct mineral components and texture are recognized and,in order of increasing degree of alteration,these are: zoneIII is rich in serpentine minerals; zoneII is rich in talc and carbonates; and zoneI is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith,although some oxides show linear correlations with Mg O. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zoneI and zoneIIand is up to 0.91 g/t in one sample from zoneI. We show that CO2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains,indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. The compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.     

Ordovician Intrusive-related Gold-Copper Mineralization in West-Central New South Wales, Australia

Three major types of Ordovician intrusive-related gold-copper deposits are recognized in central-west New South Wales, Australia: porphyry, skarn and high sulphidation epithermal deposits. These deposits are mainly distributed within two Ordovician volcano-intrusive belts of the Lachlan Fold Belt: the Orange-Wellington Belt and the Parkes-Narromine Belt. Available isotopic age data suggest that mineralization of the three types of deposits is essentially coeval with the Ordovician intrusive rocks (480-430 Ma).Porphyry gold-copper deposits can be further divided into two groups. The first group is associated with monzonite showing shoshonitic features, represented by Cadia and Goonumbla. The second group is associated with diorite and dacite, including the Copper Hill and Cargo gold-copper deposits. Gold skarn is associated with Late Ordovician (430-439 Ma) monzonitic intrusive complexes in the Junction Reefs area (Sheahan-Grants, Frenchmans, and Cor-nishmens), Endeavour 6, 7 and 44, Big and Little Cadia     

建筑地质环境评价

本文从“风水”一词的由来、发展演化过程,论述了其迷信色彩和科学成分,建议破除迷信,开展建筑地质环境评价,并提出了建筑地质环境的10个评价条件。     

广西邕江流域早全新世贝丘遗址的生业形态和定居模式分析: 来自植物遗存的综合证据

河旁贝丘遗址是广西新石器时代早中期的一种重要文化遗址类型,目前对其生业状态和定居模式的研究还相对薄弱。本研究使用综合性植物考古学研究方法,对邕江流域豹子头、石船头和那北咀这3个河旁贝丘遗址进行了大遗存分析、薄壁组织（parenchyma）遗存分析、炭屑分析以及淀粉粒和植硅体等微体遗存分析。本研究的分析结果与以往的研究成果表明,邕江流域河旁贝丘群体的食谱范围非常广泛,且包含了多种回报率档次差异极大的食物资源,其生业模式应为广谱采集。磨石、陶器、炭化食物遗存的发现以及对棕榈的强化利用行为,表明贝丘群体已经具备改造环境、提高多种食物资源回报率的能力,但是对植物资源的强化利用程度仍然较为初级。贝丘群体掌握了新的食物收获和处理技术,并且可能意识到某些资源的可预测性,这为贝丘群体降低流动意愿乃至定居下来提供了基础条件。贝丘遗址可能是作为采食群体定期或季节性的定居点,以便于采集坚果、棕榈、块茎和贝类等资源,而非作为永久性的定居居址。

     

珠三角地区长时间序列气溶胶时空变化特征分析

本文通过对2000年—2013年长时间序列的MODIS气溶胶产品进行统计,分析了珠三角地区气溶胶光学厚度(AOD)和细粒子光学厚度(FAOD)的空间分布特征以及年度和季节变化特点,有助于深入研究珠三角地区颗粒物污染水平变化及颗粒物的排放与输送等。研究结果显示珠三角地区中部为AOD高值区,东西两翼地区为AOD低值区。AOD和FAOD的最高值通常分别出现在春季和秋季,最低值则通常都出现在冬季。2006年之后,珠三角地区大气气溶胶总消光虽在部分年份仍有反弹上升的现象出现,但已有明显降低。然而,该地区细粒子消光在2000年—2012年期间则呈逐年增加的趋势,且其空间差异性也越加显著,细颗粒物污染仍需进一步控制。     

Multiscale mechanical properties of shales: grid nanoindentation and statistical analytics

Acta Geotechnica - The mechanical properties of shales, a type of heterogeneous and multiphase composite, are of multiscale characteristics in nature. A large number of indentation measurements...     

内蒙古牙克石市秧草沟铅锌银钼矿化探特征及找矿意义

秧草沟铅锌银钼矿位于植被覆盖严重、基岩裸露零星的大兴安岭林区,该铅锌银钼矿床是在1︰1万土壤测量及其所圈定的化探异常查证基础上,通过地表槽探工程揭露、中深部钻探工程验证发现的,现已圈定矿体27个,初步概算铅锌银、钼资源量已达中型矿床规模。该矿区的找矿经验对在地表覆盖厚、基岩裸露稀少的林区开展找矿工作具有指导意义。     

河北省矿产资源前景及对策分析

本文在论述我省矿产资源现状的基础上,对矿产资源远景进行简要分析,提出了合理开发和利用现有矿产资源的几点建议,以期促进我省地质研究和矿产资源的开发利用。