东北太平洋东部CCB53孔沉积物Mn元素活化、迁移和沉淀与沉积环境演化的统一

本文引用地质矿产部“七五”东北太平洋CCB53孔柱状沉积物（＜63μm）的元素地球化学分析数据,采用“标准元素对比值法”定量分离Mn元素在不同物源（陆源、生物源、热液源和自生源）中的绝对含量,确定Mn元素地球化学本底,提取CCB53柱状沉积物中Mn元素的正、负异常。据此讨论了Mn元素发生活化、迁移和再沉淀的时间演化规律,即从沉积物的底部到顶部（22．42～0Ma）,Mn元素经历了四个活化、迁移和沉淀旋回,分别为840～320、320～170、170～120和120～0。Mn元素的正、负异常分布与自生源组分和氧化还原环境的变化对比分析表明,Mn元素正、负异常分布与自生源组分的高→低变化规律和氧化还原条件的周期振荡紧密相关。早期成岩过程中发生的氧化还原环境的振荡是元素发生活化、迁移和沉淀的动因。     

Incorporation of Transition and Platinum Group Elements (PGE) in Co-rich Mn Crusts at Afanasiy-Nikitin Seamount (AFS) in the Equatorial S Indian Ocean

Of the 12 elements enriched in Co-rich Mn crusts from the Afanasiy-Nikitin Seamount in the Equatorial S Indian Ocean, Mn, Fe and Co are enriched by a factor of ~10⁹ compared to their concentrations in seawater whereas Ni and Cu are enriched by a factor of ~10⁷ and the PGE and Au by a factor of ~10⁵ to 10⁷ compared to their concentrations in seawater. The relatively high concentration of Pt in the crusts reflects its occurrence as fine-grained particles in the crusts rather than adsorption of the elements from seawater.     

深水型水库环保疏浚对水质的影响及敏感参数研究——以通济桥水库为例

国内对于作为饮用水水源地并具有水温分层特征的深水型水库环保疏浚,缺乏长期实测评价工程前后水质变化规律以及易于发生变化的水质参数的实例.因此,对于这种类型的环保疏浚,如何进行效果评价并在工程实施中控制敏感参数成为一个没有解决的问题.本文以典型的饮用水水源地、深水型的通济桥水库为对象,通过长期水质监测,研究了环保疏浚的影响.结果发现环保疏浚对总氮（TN）削减起到较好的效果,但是疏浚期间总磷（TP）浓度明显上升,完工半年后TP浓度仍略高于往年同期水平.其中,坝前库区TN浓度降低至疏浚前多年同期均值的56%~87%,而TP浓度却为疏浚前的1.87倍以上.并发现浊度、TN、TP和锰（Mn）对于环保疏浚敏感响应.其中,TP波动与底泥扰动引起的浊度变化有密切的关系;坝前库区疏浚新生底泥Mn含量较高（1251.25 mg/kg）,夏季水温分层加剧了库底水体的厌氧状态,是Mn出现异常的主要原因.以通济桥水库为鉴,建议深水型环保疏浚重点考虑底泥扰动及后续季节性水温分层对水质控制效果产生的影响.     

广西东平沉积锰矿地球化学特征及成矿物质来源研究

东平沉积锰矿为桂西南的一个中大型锰矿床,大地构造位置处于滇桂地洼系,主要的含矿层位是下三叠统北泗组,沉积相主要为浅海陆棚相。本文通过研究东平锰矿矿床地球化学特征,结合东平锰矿的岩相古地理、含锰岩系、矿石矿物等特征,阐明矿床成因及成矿物质来源。测试结果表明,含锰岩系富集Co、Ni、Ba、Sr、Ti、V等元素,w(Ba)/w(Sr)值在3~7之间,N(Fe)/N(Ti)、N(A1)/N(Al+Fe+Mn)值分别为6~59、0.26~0.66,w(Co)/w(Ni)值在0.4~1之间;w(ΣREE)为36.9×10~(-6)~774.1×10~(-6)之间,w(Nb)/w(Ta)值为9~22(平均13),w(Y)/w(Ho)值为26~35,HREE与LREE分馏不明显;微量元素的图解均显示成矿过程中有海底热液的加入,说明矿床的形成受稳定的大地构造环境与局部海底火山热液喷流活动的控制。     

南部非洲锰矿成矿规律与资源潜力

锰作为一种重要的金属矿产,广泛应用于各种工业领域。世界锰矿资源总量丰富,但分布极不均衡,主要分布在南非、乌克兰、巴西、澳大利亚等国。中国锰矿资源具有总量大、平均品位低、开采难度大等特点,为满足国内需求,中国每年需从海外进口大量锰矿。南部非洲地区锰矿资源丰富,主要有海相沉积受变质型、海相沉积型、热液型及表生型锰矿4种成矿类型。其中,海相沉积受变质型和海相沉积型最重要,依据含矿岩系特征又进一步将其划分为BIF岩系型锰矿、黑色页岩系型锰矿及硅-泥-灰岩系型锰矿。南部非洲原生锰矿成矿时代主要集中在2.2~2.0 Ga,与Eburnean造山运动时代耦合;空间上主要分布在古陆块边缘,成矿背景以弧后盆地及边缘盆地为主。南部非洲地区锰矿成矿地质条件优越,且总体找矿勘查程度较低,资源潜力巨大。     

贵州省从江县高增锰矿矿床地质特征及成因浅析

从江县高增锰矿严格受控于地层层位和古构造,矿体呈层状、似层状产于南华系大塘坡组底部灰色、浅黑灰色含炭粉砂质粘土岩中,本文总结分析了高增锰矿床矿床地质及矿石质量特征、分析研究成锰期沉积环境,认为该矿床属浅海海湾相沉积型碳酸锰矿床,为黔东及邻区又一典型南华纪“大塘坡式”锰矿床。     

Space-time distribution of manganese ore deposits along the southern margin of the South China Block,in the context of Palaeo-Tethyan evolution

The evolution of the Palaeo-Tethys Ocean played an important role in the Palaeozoic tectono-metallogenesis in Southeast Asia, in which diverse blocks amalgamated due to its closure. Previous researches focused mostly on endogenic metallogenesis related to the evolution of the Palaeo-Tethys Ocean. However, the tectonic control on the numerous Mn ore deposits in the southwestern South China Block (SCB) developed during Palaeo-Tethys evolution is largely unknown. In this article, we review Palaeo-Tethys evolution and define its four evolutionary stages from initial opening, maturity, incipient subduction, to post-closure. This study further investigated the geology and palaeogeography of Mn ore deposits in Upper Devonian, lower Carboniferous, middle Permian, and Lower-Middle Triassic formations in the southwestern SCB. We show that each of the four Mn metallogenic episodes was a response to each of the four evolutionary stages of the Palaeo-Tethys Ocean. Wall rocks of orebodies transitioned from chert-mudstone-carbonate in the Devonian, Carboniferous, and Permian to siltstone-mudstone in Lower-Middle Triassic. The ores of the four episodes of Mn mineralization are composed primarily of rhodochrosite, manganocalcite, and rhodonite. The carbonate C–O isotope and ore trace element composition data suggest that ore-forming fluids were dominated by seafloor water with involvement of magmatic hydrothermal fluids and organic matter as well. Palaeogeography reconstructions indicate the Mn-ore deposits formed along the margins or in the centre of the abyssal basins. Despite the diverse tectonic settings of the four Mn mineralization episodes, it is proposed that the crustal sagging, restricted seafloor environment, and hydrothermal activities that occurred in the southwestern margin of SCB contributed to Mn mineralization.     

东太平洋锰结核中叠层石纹层周期信号的谱分析及其意义

利用光学显微镜对一取自东太平洋的光滑型锰结核中的叠层石纹层进行分级统计，得到纹层带、纹层组和纹层对的韵律周期分别约为500μm、50－42．8μm和11－9．0μm。利用电子探针线扫描分析获取了锰结核磨光面上一生长剖面（长0．7mm)的Si、Al、Fe、Mn元素的含量变化序列，运用功率谱分析方法识别出上述4种元素序列具有111．3μm、46．5－40．6μm、24．9－28．1μm、23．1－23．9μm和11．7－13．4μm的显著振荡周期。除了纹层带周期由于受剖面长度限制没有出现外，显微镜下统计得到的叠层石的纹层组和纹层对周期在元素序列的功率谱分析结果上均得到了反映。通过对锰结核生长速率的讨论，认为锰结核的纹层韵律很可能与地球轨道参数的周期性变化有关，纹层组周期可能对应地球轨道的黄赤交角变化周期，纹层对周期可能对应地球轨道的半岁差周期，所研究剖面叠层石的生长速率约为1．134mm/Ma。     

辽宁省锰元素分布规律及锰矿床潜力评价

通过研究不同地质构造单元、不同时代地层和不同岩石类型中锰元素分布特征,认为辽西台陷和松辽拗陷区可作为形成锰矿的重要矿源地体.结合辽宁省富锰地层特征和锰矿床地质特征,认为铁岭组含锰灰岩岩层是沉积锰矿找矿的重要标志,其分布的辽西地区可划为辽宁省境内大型浅海沉积锰矿成矿远景区;辽东、辽南白垩系富锰页岩分布的地区有望找到中到大型河湖相沉积锰矿床;火山热液锰矿可在朝阳、锦西以西地区寻找,其矿源层为串岭沟组石英砂岩,高于庄组含锰细砂岩,大红峪组、铁岭组、洪水庄组富锰碳酸盐岩,成矿热液为酸性岩浆提供.     

Columnar microbialites of the upper Miocene of Mallorca (Spain): A new morphogenetic model based on concurrent accretion and bioturbation – uncommon or overlooked?

Bioturbation has long been considered an antagonist of microbialite development and preservation, because metazoan grazing and burrowing destroy benthic microbial communities. However, metazoan bioturbation, in conjunction with microbial accretion, may have had a significant role in the morphogenesis of some columnar microbialites, as suggested by the case study presented and by some Phanerozoic and Upper Proterozoic analogues discussed here. Late Miocene in age, the studied microbial biostrome developed in a western Mediterranean restricted shallow-water platform dominated by grainy sediments and with a notable influence of bioturbation. This study is focused on the complex accretionary history of the columnar microbialite biostrome and on its striking dark grey colour, which is attributed to Mn-oxyhydroxides precipitated during meteoric diagenesis linked to subaerial exposure. The characteristic columnar structure of the microbialite biostrome has features consistent with an accretionary origin of the columns, but also has features suggesting metazoan disruption. Therefore, a new morphogenetic model for columnar microbialites is presented, highlighting the concomitant roles of microbial accretion, bioturbation and grainy sediment infill of the intercolumn space. Whether this model is an exception or a rule, should be tested on other examples of Phanerozoic and Upper Proterozoic columnar microbialites. Nevertheless, this model is a step forward in understanding the complex microbe–metazoan interactions as constructive coexistence rather than just as destructive competition.