广西宁明组植物化石中黄铁矿及其沉积意义

对化石中的黄铁矿进行研究,有助于明确生物的化石化过程以及期间的沉积微环境。利用光学显微镜和扫描电镜,对广西宁明组植物化石中保存的黄铁矿进行了分析,发现离散型单晶和成群的莓状体共同保存。单晶绝大多数为无规则至球状体,晶棱不明显,表面可见凹点;少数为八面体,晶棱明显,表面光滑;单晶直径为0.79~1.58 μm;莓状体为圆球状,粒径为7.23~14.95 μm,S/Fe原子个数比的均值为1.54。莓状体的粒径大小和变化幅度均处于低值段,其S/Fe原子个数比值小于2,结果均说明当时植物体上、下表皮间为一种贫氧的水体环境,并在短时间内形成了莓状体。植物化石上、下表皮间由于未保存组织结构,而被大量的、近似层状分布的黄铁矿单晶和莓状体充填,结果支持了化石内莓状体形成与有机质降解之间存在着必然联系。     

龙门山地区中泥盆统养马坝组风暴沉积中的遗迹化石及其环境意义

龙门山地区泥盆纪地层中含有种类丰富、数量众多的海相遗迹化石。以野外剖面实测为基础,对北川甘溪石沟里剖面中泥盆统养马坝组风暴沉积中的遗迹化石进行了系统描述,共识别出5种类型的遗迹化石属种,包括Chondrite、Changchengia、Rhizocorallium、Skolithos和Zoophycos。根据遗迹化石的组合特征,将其划分为Chondrites-Zoophycos遗迹化石组合类型,反映了受风暴影响的浅水沉积环境。通过遗迹化石的分布位置、相互间的切割关系,建立了龙门山地区石沟里剖面养马坝组风暴岩中各种遗迹化石形成的先后顺序,依次为Chondrites、Zoophycos、Rhizocorallium、Changchengia和Skolithos。发育于风暴岩中的Chondrites和Zoophycos遗迹化石,具有鲜明的机会种特征,对沉积环境有重要的指示意义。保存于龙门山地区泥盆系养马坝组风暴岩中丰富的具细小分支直径的Chondrites遗迹化石,反应水体氧含量并非控制Chondrites潜穴直径大小的唯一控制因素,可能与造迹生物生活环境的恶劣与否间存在着一定关系;风暴沉积中发育的Zoophycos遗迹化石,指示其在泥盆纪可以沉积于浅海环境。     

贵州独山泥盆系大河口组遗迹化石Teichichnus及其地质意义

贵州独山中泥盆统大河口组中含有丰富的遗迹化石Teichichnus Seilacher(包括5个遗迹种：潜穴及蹼状构造直立排列的Teichichnus rectus Seilacher，潜穴管具有二分枝现象的T．palmatus Seilacher，潜穴管近口孔部位膨大呈葫芦状的T．majiatunensis Wang，潜穴管近口孔部向上折曲的T．sinuosatus Wang和蹼状板构造呈S状扭曲的T．aff．sigmoi—dalis(Seilacher)。本文主要讨论其生态环境意义及地质意义。通过野外观察及研究分析认为：与层面斜交的Teichichnus潜穴管为造迹生物居住和觅食的活动场所，为Seilacher(1967)的Cruaiana遗迹相的典型分子；蹼状构造的形成系造迹生物在保持一定生态位下与沉积或侵蚀作用相关，并可确定地层的顶底面；潜穴管口孔的弯曲程度和膨胀程度是区分遗迹种的重要特征，可利用Teichichnus的遗迹种和其潜穴管与层面之间的交角分析其沉积环境的微相变化；Teichichnus潜穴管口孔多迎着主水流方向发育，可指示古水流的方向。     

河南西峡盆地上白垩统河流及湖泊沉积中的遗迹组构

河南西峡盆地上白垩统马家村组沉积厚度巨大,达1 960 m,由辫状河沉积、曲流河沉积和湖泊沉积组成。在河流与湖泊沉积中,发育丰富的遗迹化石,共6种类型,分别为Skolithos linearis、Cylindricumichnosp、Palaeophycus tubularis“J”形潜穴、垂直分枝潜穴和垂直螺旋潜穴。从形态分析,大多数为居住迹,按照遗迹化石产出岩层的岩性、扰动特征和残留遗迹等总体特征,将所发现的遗迹化石层划分为两类遗迹组构,即软底组构和僵底组构。前者主要发育在纹层状极细砂岩和粉砂岩中,潜穴密度大,属种单一,包括Skolithos组构和Palaeophycus组构;后者主要发育在厚层泥岩中,潜穴密度较大,类型稍多,包括由Cylindricum ichnosp、垂直分枝潜穴J形潜穴和垂直螺旋潜穴所组成的遗迹组构。与报道过的其他地区陆相遗迹化石的对比表明,随着时间的推移,河流沉积中的组构特征在白垩纪有明显变化,而浅湖沉积中的遗迹组构表明造迹生物的扰动能力显著加强。     

贵州独山下泥盆统丹林组陆相地层中的U形潜穴

具蹼状构造的垂直 U形潜穴 Diplocraterion广泛产出于全球寒武纪—古近纪的滨浅海相中 ,被认为是 Seilacher(196 4 ,196 7)的 Skolithos遗迹相的主要分子 ,也见于中—新生代的河湖相中 ,被视为高能环境的重要分子。Diplocraterion在古生代陆相地层中的发现仍是首次。产于贵州独山丹林组陆相地层具有水平层理的黑色泥岩中的 Diplocraterion dushanensis ichnosp.nov.其近于平行的 U形栖管由许多的节管组成 ,节管和蹼状构造可能系造迹生物的居住潜穴阶段性地随沉积物的增厚而向上移动的过程中所形成 ,其造迹生物主要生活于泛滥平原相对平静贫氧的水体环境中。     

松辽盆地腰南5井上白垩统嫩江组一段遗迹化石组合及其沉积环境

【研究目的】松辽盆地上白垩统嫩江组中含有丰富的遗迹化石,但相关研究主要集中于松辽盆地北部。通过鉴定遗迹化石还原松辽盆地南部嫩江组一段沉积环境,为该地区后续遗迹化石研究提供证据支持。【研究方法】通过观察腰南5井嫩江组一段岩心,发现了Chondrites及Planolites等共计2属,2种遗迹化石,建立了Chondrites-Planolites遗迹化石组合;结合遗迹化石围岩岩性、潜穴规模、测井曲线记录对造迹生物生存习性进行分析;通过腰南5井采样,分析样品中铀、钍、钒、镍与钴含量,使用铀/钍、钒/（钒+镍）与镍/钴等手段对嫩一段遗迹化石保存层位的古氧相进行还原。【研究结果】研究认为Chondrites-Planolites遗迹化石组合形成于水动力较小的深水环境;古氧相数据分析表明,腰南5井嫩一段泥岩样品铀/钍指示常氧环境,钒/（钒+镍）与镍/钴指示贫氧-缺氧环境。【结论】腰南5井嫩一段遗迹化石组合保存于泥岩且潜穴直径小,遗迹化石丰度低,表明水体含氧量低。结合古氧相数据和测井曲线分析,认为造迹生物的生活环境为水动力较弱且水体氧含量低的半深湖相环境。     

藏北比如中侏罗世马里组遗迹化石的发现及其意义

描述了藏北比如地区中侏罗统马里组的遗迹化石8属8种（其中包括1个新遗迹属和2个新遗迹种）：表面光滑无饰、具有较薄管壁和密集新月形回填构造的不分枝水平潜穴Beaconites biruensis ichnosp.nov.,沿层面分布的哑铃形潜穴Bifungites cf. hanyangesis Yang,圆柱状厚管壁的分枝并构成假网状的潜穴Biruichnus maliensis ichnogen. et ichnosp. nov.,窄长的、内肢抓痕的二叶形遗迹Cruziana ichnosp.,以垂直于层面的圆管为中央放射出排列不规则且粗细变化较大细管的多分枝潜穴系统Micatuba cf. verso Chamberlain,平行或微斜交于层面的圆柱状微弯曲或弯曲的潜穴Palaeophycus ichnosp.,栖管段有规律地交替向两侧分叉呈Z字形或锯形的三维潜穴系统Treptichnus cf. bifurcus Miller,平行层面的、具有蹼状构造的简单U形潜穴Rhizocorallium ichnosp.。西藏比如地区中侏罗统马里组有大量的波状层理、透镜状层理和脉状层理等潮汐层理,发育侵蚀构造,上部紫红色含砾粗砂岩、长石砂岩发育,为滨岸相沉积。马里组的遗迹化石以浅层内生迹的爬行觅食潜穴和居住滤食性潜穴占有优势,也见有节肢动物的爬行迹和系统觅食潜穴,且产遗迹化石的层位见小型干涉波痕,为近海浅水中至低能的沉积环境。     

滦河三角洲潮坪环境现代生物遗迹组合及其分布特征*

现代生物遗迹的特点、分布和组合特征及其与沉积环境、沉积物性质的关系,对遗迹化石及古环境研究具有重要的实证价值,但现代生物遗迹研究起步较晚,国内研究成果较少。文中论述了滦河三角洲潮坪环境中现代生物遗迹的组成、组合与分布特征,并分析了遗迹组合与沉积环境的关系。研究表明: (1)层面遗迹以节肢动物、环节动物、腹足动物的爬行迹和拖迹为主; 层内遗迹包括垂直或高角度倾斜于层面的潜穴、平行于层面的潜穴,以居住迹为主,丰度高,类型多样。(2)建立了3种生物遗迹组合: 遗迹组合I以Y形和垂直管状潜穴为特征,局部丰度较高,表层潜穴和层面拖迹不发育,造迹生物主要为沙蚕和螃蟹,沉积物底层具有砂含量较高、水动力强、有机质含量低的特点,显示其出现于三角洲潮坪砂质沉积环境;遗迹组合Ⅱ以各种形态的层内潜穴和大量的层面爬行拖迹为特征,层内潜穴包括垂直管状、J形、U形、Y形和分枝形潜穴,丰度高,造迹生物主要是沙蚕和螃蟹,层面遗迹常见爬行拖迹和足辙迹,造迹生物主要为沙蚕、螃蟹、扁玉螺、寄居蟹,沉积物底层具有高泥质含量、高含水率和高有机质含量的特点,形成于三角洲潮坪中低潮区;遗迹组合Ⅲ以与层面近似垂直和与层面近似平行的层内潜穴以及大量的层面运动迹为特征,与层面近似垂直的潜穴包括垂直管状、J形、U形、Y形和复杂分枝形潜穴,造迹生物主要是螃蟹、泥甲虫及其幼虫, 与层面平行的表层潜穴主要是蝼蛄、泥甲虫及其幼虫营造的,层面上的运动迹常见为螃蟹足辙迹和鸟类足迹,沉积物底层具泥质含量高、含水率低、有机质含量高、底质固结程度较高的特点,产生于三角洲潮坪高潮区。(3)基于对遗迹组合和分布特征及其与底层性质和沉积环境关系的分析,建立了三角洲潮坪生物遗迹组合的沉积环境分布模式。该研究成果既可作为古代三角洲潮坪沉积环境的判识依据,也可为相似遗迹化石组合的沉积环境恢复提供佐证。     

华北寒武纪—奥陶纪豹皮状碳酸盐岩系生物扰动成因

华北地区寒武系和奥陶系发育了大量的生物扰动白云岩/生物扰动灰岩,选择两个代表性剖面——河南登封寒武系剖面和山西兴县奥陶系剖面进行碳酸盐岩系生物扰动成因研究。河南登封寒武系第二统朱砂洞组中的遗迹化石较单一,主要为Thalassinoides、含有少量Planolites;山西兴县中奥陶统马家沟组五5亚段中遗迹化石较丰富,识别出的遗迹化石共7个遗迹属,分别为Arenicolites、Cylindricum、Helminthopsis、Lorenzinia、Planolites、Teichichnus、Thalassinoides,其中Thalassinoides占主导地位。朱砂洞组主要为滨岸碳酸盐潮坪相,中奥陶统马家沟组五5亚段主要为局限台地相。通过野外地质考察及室内相关实验手段及方法,利用偏光显微镜、扫描电镜对生物潜穴及围岩进行了宏观和微观结构分析,发现生物潜穴内部主要为白云石,基质围岩主要为方解石,生物潜穴在野外露头上表现为颜色不一的斑块状。两个剖面大量发育遗迹化石Thalassinoides(海生迹),Thalassinoides的三维潜穴系统为白云石化流体提供了良好的运移通道,为回流渗透作用提供了有利条件,促进潜穴充填物白云石化,从而形成了大量豹皮状的生物扰动白云岩。     

山东山旺中新世硅藻页岩中的遗迹化石

山东山旺中新世湖相沉积硅藻页岩下部，首次发现无脊椎动物潜穴遗迹化石。本文描述了这一新遗迹属及新遗迹种，定名为硅藻山旺迹讨论了遗迹动物的行为习性和沉积环境。该遗迹化石保存为全浮雕，为觅食迹。新遗迹特征为平直和销弯曲的管状潜穴。潜穴一般可不分枝或二分枝，二分枝时两侧枝近相互平行延伸，潜穴直径２－２．５ｍｍ，沿长度粗细变化不大，估计潜穴动物身体粗细与潜穴相适应，推测可能是由湖生的寡毛动物蠕虫类所形成。     

有孔虫壳体内草莓状黄铁矿成因及其地质意义——以湖北雁门口地区栖霞组有孔虫化石为例

在湖北省京山县雁门口地区栖霞组上部的含泥灰岩中存在丰富的节房虫科底栖有孔虫化石,主要有节房虫属、厚壁虫属和郎格虫属,壳体均被草莓状黄铁矿充填。对其系统的显微镜、扫描电镜观察和黄铁矿的能谱分析结果发现,黄铁矿草莓体直径最大为15 μm,平均约10 μm,硫铁原子比值（S/Fe）为1.90±0.10,表明在黄铁矿形成过程中,有孔虫壳体空腔内呈轻度- 中度贫氧的微环境。在分析该类黄铁矿成因的基础上,认为有孔虫壳体内的黄铁矿在指示沉积环境和保存环境方面具有局限性。     

Pyritization of tubes and burrows from Late Pleistocene continental shelf sediments off North Norway

Four different types of pyritized tubes and three types of pyritized burrow fillings are described from Pleistocene glaciomarine sediments in Andfjorden, northern Norway. The tubes and burrows probably originated from tubicolous and burrowing polychaetes respectively. The decomposition of the organic matter in the tubes and burrows created a reducing micro-environment favouring precipitation of pyrite. By comparison with Holocene tubes from marine sediments in Andfjorden and FugloSyfjorden, it is seen that pyritization commenced with isolated spherules. These spherules with incipient pyrite crystals and framboids were formed mainly on the inner wall of the tube. Presence of a monosulphide in the Holocene Fugløyfjorden material suggests that the pyritization process has reached a later phase; the final result would be a completely pyritized trace fossil. It is shown that single pyrite crystals (octahedra) generally attain greater size in the burrow fillings than in the tubes. The microstructure found in some of the pyritized tubes is interpreted as a reflection of the microstructure in the original wall. Finally, the implications for the depositional environment in Pleistocene in Andfjorden is investigated with reference to the benthic skeletal macrofaunal assemblage in the sequence. The pyritized trace fossils occur frequently in an opportunistic assemblage from a period (c. 14,000–13,000 yr BP) characterized by some oxygen deficiency. Later (13,000–10,000 yr BP) they play a minor role in an established assemblage under improved oxygen conditions.     

Pyrite and oxidized iron mineral phases formed from pyrite oxidation in salt marsh and estuarine sediments

We used scanning electron microscopy and energy dispersive X-ray analysis to examine sediments from vegetated portions of three salt marshes, the Great Sippewissett Marsh (Cape Cod, MA), Sapelo Island (Georgia), and the Hackensack Meadowlands (N.J.), and from the sediments of an estuary, Newark Bay (N.J.). Pyrite particles were abundant in sediments from all sites. Both fine grained pyrite crystals and framboids were found. Single, fine grained crystals (diameter = 0.2 to 2.0 micrometers) predominated in all samples, strong evidence for rapid formation of pyrite.We also found both microcrystalline and framboidal iron-oxyhydroxide phases in many of the sediment samples. This is evidence of pyrite oxidation within the sediments and suggests that iron is conserved in salt marshes even as pyrite is oxidized. The thermodynamic stability of iron phases in marsh sediments, and recent pyrite oxidation studies in coal, suggest goethite as the crystalline iron-oxyhydroxide phase present. In addition, we sometimes found a red amorphous coating on grass roots from the Great Sippewissett and Sapelo Island marshes. This coating is likely a form of hydrated iron (III) oxide.     

Formation process of pyrite polyframboid based on the heavy-metal analysis by micro-PIXE

Pyrite framboid in sedimentary rocks could be concerned with arsenic contamination in groundwater of acidic environment and has been studied for the formation process of its unique morphology. However, not much has been discussed about the formation process based on the heavy-metal distribution in pyrite framboids and their aggregates. To reveal the formation process of pyrite framboids and their aggregates, mudstone from the Late Cretaceous Hakobuchi Group, central Hokkaido, Japan, are investigated for mode, petrographical, mineralogical, and micro-PIXE (particle-induced X-ray emission) analysis in this study. Spherical and sub-spherical pyrite framboids observed in polyframboids can be divided into two types based on the diameter of framboids (D) and the average diameter of microcrystals (d) within framboids: type 1, ranging from 2 to 9 μm and from 0.4 to 0.9 μm, respectively, and type 2, ranging from 8 to 50 μm and from 0.5 to 1.8 μm, respectively. Based on the quantitative traverse analyses and 2-D elemental mapping results by micro-PIXE, heterogeneities in the concentrations of heavy metals within the analyzed aggregations of pyrite are exhibited. On the basis of the As and Pb zoning patterns, the time range and chronological stages of pyrite-aggregation growth are revealed.     

Arsenic in framboidal pyrite from recent sediments of a shallow water lagoon of the Baltic Sea

Arsenic is a redox‐sensitive element of environmental relevance and often enriched in iron sulphides. Because sediments from the Achterwasser lagoon, a part of the estuarine system of the river Oder, south‐west Baltic Sea, show unexpectedly high pyrite concentrations of up to 7·5 wt% they were used to investigate the influence of authigenic pyrite on the mobility and burial of As in the coastal environment. Micro‐X‐ray‐fluorescence measurements of 106 micrometre‐sized pyrite framboids from the anoxic sediments show highly variable As concentrations ranging from 6 to 1142 μg g^?1. Even within a 1 cm thick layer, the As concentration of different framboids varies greatly and no clear depth trend is visible throughout the 50 cm long sediment core. Pyrite can account for 9 to 55% (average 22%) of the total As budget of the sediments and the degree of trace metalloid pyritization for As ranges from 26 to 61%, indicating that authigenic pyrite formation is an important process in the geochemical cycling of As in coastal sediments. High‐resolution micro‐X‐ray fluorescence mapping of single pyrite grains shows that As is distributed inhomogeneously within larger framboids, suggesting changing pore water composition during pyrite growth. X‐ray absorption near edge structure spectra indicate that As is usually present as As(‐I) substituting S in the pyrite lattice. However, in samples close to the sediment/water interface a considerable part of As is in higher valence states (+III/+V). This can be explained by frequent re‐suspension of the surficial sediments to the oxic water column due to wave action and subsequent re‐deposition, leading to the adsorption of As oxyanions onto pyrite. Although reduced As(‐I) becomes more important in the deeper samples, reflecting decreasing redox potential and a longer time since deposition, the occurrence of oxidized As species (AsIII/AsV) in pyrite in the anoxic part of the sediment suggests formation under dysoxic conditions.     

北大西洋Logatchev热液区多形貌黄铁矿特征及其意义

北大西洋Logatchev热液区产出的黄铁矿形貌丰富、成分各异,极具特殊性和代表性.运用扫描电镜和电子探针系统观测黄铁矿矿物学特征,发现粒状黄铁矿粒径不一,具高Fe、S,低微量元素的特点;草莓状黄铁矿见有松散莓体、球形-次球形莓体和自形结构莓体,其Cu含量总体较高,不同晶体特征的莓体成分存在差异;胶状黄铁矿见有多层环带,内核到环带由纳微米晶体聚合生成,由内到外成分具有S/Fe比、Zn含量减小,As含量增大的趋势.分析认为早期粒状黄铁矿是在较高温度下的热液体系中直接形成,随热液作用衰减,生成的粒状黄铁矿多呈纳-微米晶产出;草莓状黄铁矿是由松散纳-微米晶逐步聚集形成,受溶液过饱和度影响,莓体粒度和聚集程度存在差异;胶状黄铁矿多晶聚集环带生长方向是由内向外的,聚集程度差异指示沉积环境的反复交替.研究区多形貌黄铁矿具有由分散的微晶→多晶聚合体→自形单晶的完整演化系列特征,对于解读现代海底热液活动的方式和特点,揭示纳米晶体-宏观晶体的演化过程有积极意义.      

Morphology and formation mechanism of pyrite induced by the anaerobic oxidation of methane from the continental slope of the NE South China Sea

In order to understand the response of authigenic pyrite to gas hydrate geo-systems, pyrite tubes or rods at the sulfate–methane transition (SMT) zone of core GC10 from the northern continental slope of the South China Sea (SCS) were investigated. In situ X-ray diffraction (XRD) results show that the pyrite tube consists of pyrite micro-crystals with trace amount of graphite in the inner tube. Scanning electron microscope (SEM) observations of pyrite tubes indicate various aggregations in the form of framboidal, euhedral, and colloidal pyrite microcrystals. Typical framboidal pyrite is considered as packing of octahedral microcrystals. Interestingly, many framboids in the tubes consist of round or irregular microcrystals and have an outer crust that consists of secondary pyrite. The size of the framboids in the inner wall of the tube is larger than that in the middle wall or foraminifer-filled pyrite. High-resolution transmission electron microscopic (HRTEM) images show marcasite lamellae defects in the spherulitic pyrite crystals, which reveal different solution conditions during the pyrite precipitation. Nano-foil-like graphitic carbon was observed to be closely associated with the pyrite spherules. The occurrence of both marcasite layers and nano-foil-like graphitic carbon suggest that the migration of methane from deep sediment. It is suggested that the formation of pyrite serves as a catalyst during the reaction from methane to elemental carbon under the anaerobic oxidation of methane. Meanwhile, this reaction results in local acidification of the solution inside the pyrite tubes, which favors marcasite lamellae growth on the host pyrite substrate.     

Sulfide minerals in Seelyville Coal III,Chinook Mine,Indiana

Sulfide minerals in coal bed III at the Chinook Mine, Indiana, are pyrite, marcasite, and rarely sphalerite. Pyrite occurs as framboids concentrated mainly in exinite, as bands or lenses in vitrinite and clay partings, as cell fillings in fusinite, and in cleats. Marcasite normally occurs in association with clusters of pyrite framboids within micro-organic remains. Sphalerite occurs exclusively in fusinite associated with cleat pyrite. The iron sulfides, which are of authigenic origin, were formed during the biochemical stage of coalification during the accumulation and compaction of peat. The factor that limited their formation in such an environment was the availability and reactivity of iron. Chemical heterogeneity in the peat swamps where the sulfides formed existed even on a microscopic scale. The iron sulfides were commonly precipitated in localized micro-environments that were favorable for their formation. The metamorphic stage of coalification did not affect the iron sulfides significantly, although it may have been responsible for the recrystallization of pyrite framboids and minor deformation of pyrite in fusinite and its local mobilisation.