塔中地区中晚奥陶世灰泥丘初步研究

塔中地区中晚奥陶世灰泥丘是在古老碳酸盐岩台地逐渐沉没过程中生长发育的。横向上,它向台地高部位层层爬坡,纵向上,为多旋回叠丘。建造灰泥砂丘的生物主要是菌藻类-奥特藻及其相近的属,尚有珊瑚、苔藓虫、层孔虫、海绵等。其岩石类型主要是泥晶凝块格架岩、泥晶凝块障积格架岩、泥晶藻凝块粘结岩。其沉积相可分为丘中心、丘前和丘间三个相带。灰泥丘的演化受控于海进速率同灰泥丘的增长速率及海水深度与浊度。     

川北旺苍唐家河剖面仙女洞组灰泥丘沉积特征及造丘环境分析

目前川北地区早寒武世微生物藻与古杯参与的生物礁(丘)发育特征存在较大争议。通过实测剖面与镜下分析,川北旺苍县鼓城乡唐家河剖面仙女洞组发育三期灰泥丘。对该剖面灰泥丘沉积特征进行精细研究认为:第一期灰泥丘发育在滑塌角砾灰岩之上,造丘生物主要为枝状和房室状附枝藻,主要岩性为砾屑灰岩、藻格架凝块灰岩和含云生物碎屑灰岩,发育丘基、丘核、丘盖和丘翼,后期演化为钙质砂泥岩结束生长。第二期生物丘发育在鲕粒滩间生屑灰岩之上,造丘生物主要为肾状藻,次为附枝藻,主要岩性为生物碎屑灰岩、藻格架凝块灰岩、漂浮砾岩和亮晶鲕粒灰岩,纵向上发育丘基、丘核、丘坪、丘盖和丘翼,最终再度沉积鲕粒灰岩。第三期灰泥丘发育在藻叠层灰岩之上,造丘生物为古杯和微生物藻,岩性主要为古杯灰岩、生物碎屑泥晶灰岩、藻格架凝块灰岩和藻叠层灰岩,发育丘基、丘核和丘盖。进一步分析三期灰泥丘的成丘环境认为第一期灰泥丘属于台缘斜坡环境内的斜坡灰泥丘低能沉积,经历三个演化阶段;第二期属于台地边缘灰泥丘,经历四期演化阶段;第三期为台缘高能鲕粒滩向陆一侧能量相对较低的台缘古杯灰泥丘沉积,经历三个演化阶段。剖面中灰泥丘多与鲕粒滩共存,构成丘滩复合体,为后期研究储集性能和油气富集关系具有重要的油气地质意义。     

北京西山下苇甸中寒武统张夏组生物丘发育特征及其地质意义

北京西山下苇甸剖面寒武系地层出露完整,中寒武统张夏组底部和顶部发育两期生物丘地层.通过野外观察及薄片鉴定发现,张夏组底部发育的生物丘为凝块石生物丘,顶部发育的为叠层石生物丘,两期生物丘的造丘生物主要为藻类.凝块石生物丘生长在低能的潮下带环境,而叠层石生物丘则形成于海水能量较高的潮间带或潮下带上部.不同的沉积环境造成了两期生物丘内部结构的差异,主要体现在造丘生物的排列方式上.根据该剖面两期生物丘的特征,总结了生物丘的发育模式,并对其地质意义进行了探讨.     

华北地台是晚寒武世沉积层序中生物丘构造研究

华北古克拉盆地中晚寒武纪沉积层序中发育的生物丘沉积构造的生物组成有隐藻类，钙藻类和非藻类多细胞生物，它们构成了隐藻凝块石生物丘简单类型和复合的五种生物丘类型。生物丘的发生，发展，灭亡过程经历了奠基期，拓殖期，泛殖期及消亡期等四个阶段，每阶段都爱相对海平面变化的控制，它决定了丘体的大小，生物组成及内部结构及周期。     

四川盆地中二叠世栖霞期微生物丘及其对沉积环境的启示

在四川盆地华蓥溪口地区首次发现了发育在二叠纪栖霞期的微生物灰泥丘,该灰泥丘以灰泥作为支撑结构;参与建筑的生物主要是菌类微生物,其次为多门类无脊椎动物,如有孔虫、腕足等,但生物物种分异度较低,丰度较高;岩石类型主要为生屑泥晶灰岩以及凝块石等;灰泥丘可划分为丘基、丘核及丘翼。根据地化分析,华蓥溪口栖霞组剖面野外样品古盐度Z值均122,且δ~(13)C0;δ~(18)O变化在-6.33‰~-4.22‰,向上δ~(18)O总体为正偏移,表明海平面逐渐下降。恢复的古水温在33.60~24.26℃。V/(V+Ni)比值为0.51228,U/Th比值为8.28205;指出华蓥溪口地区处于水体较深,水动力较弱,温度较高的超咸缺氧环境。这种环境有利于微生物丘的发育,并影响了造礁生物的发育和生长,是导致栖霞期没有发育骨架礁的原因之一。     

寒武系张夏组鲕粒滩中微生物碳酸盐岩主导的生物丘：以河北秦皇岛驻操营剖面为例

华北地台的寒武系苗岭统,大致包括毛庄组、徐庄组、张夏组和崮山组,这些组分别组成相应的三级沉积层序,在它们的顶部集中发育着鲕粒滩相灰岩而构成强迫型海退沉积,成为时间特化的相,代表着鲕粒主导的特别的寒武纪碳酸盐岩台地类型,表现在浅海陆架中大面积分布鲕粒滩,而且在这样的鲕粒滩中生长和发育着微生物碳酸盐岩主导的生物丘;河北省秦皇岛市驻操营剖面的张夏组上部鲕粒滩相灰岩中的生物丘正是上述现象最为典型的代表。虽然类似的现象曾经被描述为"藻坪"沉积,或者笼统地归为"微生物礁",但是,河北省秦皇岛市驻操营剖面的张夏组上部鲕粒滩相灰岩中的生物丘,以下现象不但将其特征化而且代表着壮观的沉积学现象:(1)在强迫型海退体系域的下部与鲕粒滩相灰岩交互产出的主要是柱状叠层石生物丘;(2)在张夏组顶部则以集中产出的均一石和树形石生物丘为特征;(3)下部的柱状叠层石生物丘中主要包括石松藻(Lithocodium)-孢网菌(Bacinella)状组构的钙化蓝细菌;(4)在上部集中产出的均一石与树形石生物丘,则发育着丝状钙化蓝细菌、基座菌(Hedstroemia)和附枝菌(Epiphyton)之类的多样化的钙化蓝细菌。由于石松藻(Lithocodium)-孢网菌(Bacinella)状组构的钙化蓝细菌是一种灭绝了的浅海生命形式,而且是不知道分类位置归属的生命形式,尤其是石松藻(Lithocodium)状组构近年来在寒武纪微生物碳酸盐岩研究中多被解释为"硅质海绵骨针的网状物"或"非骨针角质海绵骨骼纤维",再考虑到均一石自从命名以来很少描述在古老的地层记录之中,因此,驻操营剖面张夏组上部多样化微生物碳酸盐岩所主导的生物丘,以及生物丘中特别而且多样的钙化蓝细菌化石构成,为了解蓝细菌主导的光合作用微生物席复杂的钙化作用形成微生物碳酸盐岩提供了较为典型的实例。     

辽宁金州寒武系长山组生物丘沉积特征

在辽宁金州寒武系长山组顶部,发育一层厚约15 m的生物丘。宏观上,生物丘主要由凝块石和均一石组成;微观上,由致密泥晶组构和各种类型的颗粒组成。在生物丘内部,各种类型的颗粒如钙化微生物、底栖鲕粒、核形石、生物碎屑和凝块等的发育,显示了生物丘复杂的显微组构。其中,三叶虫碎屑表面的泥晶结壳,表现出建设性和破坏性泥晶化作用。泥晶中分散分布的生物碎屑,反映了生物丘形成过程中泥晶较强的黏聚作用。致密泥晶中大量黄铁矿颗粒的发育,反映了异养细菌活动对泥晶形成的贡献。生物丘内部各种类型的颗粒与黄铁矿颗粒的共生,反映了生物丘形成过程中存在复杂的微生物作用,这为微生物沉积作用的研究提供了基础素材,也为生物丘内部各种类型颗粒的研究提供了重要实例和线索。     

寒武纪芙蓉统均一石沉积组构及环境特征——以河北涞源长山组为例

均一石以隐晶质岩性、无纹层与凝块结构发育为特征,与叠层石、凝块石、树形石并列为典型的微生物岩。然而,由于均一石在1995年命名以来很少在地层记录中得到识别和描述,并且缺乏现代实例的类比物,使得关于均一石的报道极具研究价值。为研究华北地台寒武系均一石沉积组构与形成环境特征,系统性地针对河北涞源祁家峪剖面芙蓉统长山组均一石生物丘进行研究。芙蓉统长山组从下部陆棚相钙质泥岩向上变浅至浅缓坡相厚层块状泥晶灰岩,组成了一个淹没不整合型三级层序。三级层序顶部的浅缓坡相厚层块状泥晶灰岩层,代表强迫型海退过程沉积,其内部发育一系列米级均一石生物丘。研究结果表明,这些生物丘主体为致密泥晶及少量微量晶组成,其中可见到附枝菌(Epiphyton)、葛万菌(Girvanella)、肾形菌(Renalcis)等钙化微生物化石。这些钙化微生物(蓝细菌)化石的出现,代表了显生宙第一幕蓝细菌钙化作用事件的证据,同时间接的说明均一石生物丘形成于蓝细菌主导的微生物席的钙化作用过程之中。同时,生物丘内还局部集中发育底栖鲕粒与草莓状黄铁矿颗粒,表明了生物丘形成过程中复杂的微生物沉积作用机制。因此,河北涞源长山组顶部的均一石生物丘,尽管泥晶和微亮晶是其基本构成,但是各种钙化蓝细菌化石以及底栖鲕粒与草莓状黄铁矿颗粒的局部出现表明了在蓝细菌主导的微生物席中复杂的微生物活动信号,成为了解生物丘形成机制、显生宙第一幕蓝细菌钙化作用事件的典型实例。     

湖北松滋地区下奥陶统微生物岩

首次系统性地对湖北松滋地区下奥陶统微生物岩开展研究。根据微生物岩的生长方式,文中将微生物岩划分为原地生长型和非原地生长型两大类别,前者包括叠层石、凝块石,后者主要为核形石。根据几何形态特征,将研究区的叠层石分为层状、波状、柱状和丘状4种类型,新发现并命名了双锥柱状叠层石。将凝块石划分为斑状、网状和条带状3种类型,在豹斑状和网状凝块石中,发现了许多钻孔捕食软体动物Ecculiomphalus化石以及生物扰动的痕迹,文中认为这两种凝块石均属于生物扰动型凝块石。生物扰动型凝块石的发现不仅填补了国内、外奥陶纪该领域的部分空白,而且为凝块石成因的研究提供新的材料。在对各类微生物岩的沉积特征分析基础上,阐述了各类微生物岩的沉积环境,并总结其沉积环境分布模式。对微生物岩发育与中奥陶世后生动物大辐射之间的关系进行了探讨,根据早奥陶世晚期至中奥陶世初期后生动物的阶梯式和快速辐射与微生物岩突然减少的对应关系,结合研究区叠层石、凝块石中发现许多后生底栖钻孔捕食腹足类Ecculiomphalus化石等现象,认为微生物岩随时间推移而逐渐减少、衰退与后生动物丰度的快速增加有一定关系,指出食草动物不仅啃食了形成叠层石的菌藻类微生物,造成叠层石数量的不断减少,而且破坏了叠层石的生长状态,结果形成了研究区独具特征的生物扰动型凝块石。此外,作者认为,中奥陶世开始,海平面的快速上升也是研究区微生物岩减少直至消失的原因之一。     

光合作用生物膜建造的凝块:来自于辽东半岛芙蓉统长山组凝块石生物丘中的一些证据

作为一种以非纹层状组构而区别于叠层石的微生物碳酸盐岩类型,中凝块(mesoclots)是产生凝块石凝块组构关键的微结构。构成这种中凝块的离散性凝块状泥晶,似乎代表了细胞外聚合物质(EPS)复杂的钙化作用,但是,由于常常缺乏直接的微生物证据,造成其所涉及的准确成因和特殊过程还不太清楚。在辽东半岛大连金州湾和本溪田师傅剖面芙蓉统下部的长山组顶部,发育较为典型的凝块石生物丘,组成三级层序的强迫型海退体系域沉积,代表着较为壮观的沉积学现象;在这些凝块石生物丘中,毫米级别大小的暗色离散性凝块状泥晶是其最为基本的沉积组构,而且在这些凝块之中以较高密度保存的丝状蓝细菌鞘化石反映的微生物构成,意味着它们具有明显的光合作用生物膜成因。尽管穿越成岩作用过滤器去解释古代凝块石复杂的形成机理将存在着巨大的挑战,也尽管形成这些凝块石复杂的生物膜钙化作用细节需要更加深入的研究才能得到更好的了解,但是,辽东半岛芙蓉统长山组的凝块石,尤其是在凝块内较为丰富的钙化蓝细菌鞘化石所表征的直接的微生物活动证据,使其成为一个了解光合作用生物膜建造凝块的典型实例;再者,与凝块共生的三叶虫化石、底栖鲕粒和皮壳粒,以及围绕着这些多样化颗粒特别的放射纤维状方解石结壳,说明这些凝块石可能属于较厚的微生物席内多重状生物膜以及构成这些微生物席和微生物膜的细胞外聚合物质复杂的钙化作用建造物。     

Composition and origin of stromatactis‐bearing mud‐mounds (Upper Devonian,Frasnian), southern Rocky Mountains,western Canada

Stromatactis‐bearing mud‐mounds remain an enigmatic reef type despite being common in Palaeozoic ramp settings. Two well preserved Upper Devonian (Frasnian) mud‐mounds in the Mount Hawk Formation crop out side by side in the southern Rocky Mountains of west‐central Alberta and provide an opportunity to develop a new case study that can be compared with the other coeval examples, such as those well‐known ones in southern Belgium, as well as evaluate competing hypotheses for mud‐mound formation. The southern mud‐mound is 46·2 m thick and 38·6 m wide at the base, whilst the northern one is 53·3 m thick and 72·2 m wide at the base, and they exhibit three or four growth stages indicated by interfingering and onlapping geometries with flanking strata. The biota is diverse, but fossils only occupy 10·7% by volume, among which sponge spicules, echinoderms, ostracods, brachiopods and calcimicrobes belonging to Girvanella and Rothpletzella are the most common. Five microfacies are discriminated in the mud‐mounds: biomicrite, clotted micrite, spiculite, stromatolite and laminite, with clotted micrite comprising the largest proportion. There is no internal vertical or lateral palaeoecological zonation, and the presence of calcimicrobes and calcareous algae throughout indicates accretion entirely within the photic zone, in a deeper ramp setting seaward of a large carbonate platform to the east. Stromatactis is abundant and the cavities were mostly due to excavation by currents rather than physical collapse of spiculate siliceous sponges. Formation of lime mud involved a combination of multiple organisms, mechanisms and processes. Cyanobacteria were integral to mud‐mound frame‐building and accretion because they stabilized the surface, often permineralized to form Girvanella and provided organic matter that was decomposed by bacteria. This induced precipitation of micrite, forming early indurated rigid masses, evidenced by the presence of intraclasts, stromatactis cavities, isopachous marine cements, absence of bioturbation and rare synsedimentary brittle deformation. The same microbial components, invertebrate biota and clotted micrite occur in underlying strata, suggesting that there was a protracted period of potential mud‐mound initiation before the exact conditions arose to trigger it. The ramp setting, antecedent sea floor topography and relative sea‐level likely contributed together to control this. This study indicates that mud‐mound formation was controlled by a combination of processes, but they are essentially a microbial buildup.     

Foreslope stromatoporoid-renalcid bioherm with evidence of early cementation, Devonian Ancient Wall reef complex, Rocky Mountains

A small mound, 4 × 23 m in size, on the fore-reef slope of the Ancient Wall reef complex at Mount Haultain, Alberta, consists of fenestral, renalcid micrite and wackestone. Stromatoporoids are the most abundant skeletal component but do not form an organic framework. Renalcids, together with early micrite cementation, performed a supporting and stabilizing role but only rarely directly encrusted skeletal material. Many of the primary shelter voids, interparticle voids and fenestrae were filled with internal sediments and submarine micrite cements. A considerable proportion of the micrite matrix appears to be cement. The location and development of the bioherm was controlled by a local hard substrate and suitable environmental conditions. The mound developed on and around a large block within an underlying megabreccia bed soon after it was deposited in a debris flow on the fore-reef slope. It formed near wave base in about 30–50 m water depth and was subject to gentle current action. Laminar stromatoporoids grew on the flanks and top of the mound, and fenestral, renalcid micrite and wackestone accumulated in the central part. Deepening water and increased rates of mud accumulation terminated further build-up of the bioherm and it was buried by basin mud. Fenestral, renalcid micrite occurs in a number of Devonian and Lower Palaeozoic organic mounds. This study suggests that early, submarine cementation was a significant factor in the development and preservation of this distinctive lithotype.     

Crystallization pathways in the Great Artesian Basin (Australia) spring mound carbonates: Implications for life signatures on Earth and beyond

Recent studies of continental carbonates revealed that carbonates with similar fabrics can be formed either by biotic, biologically-induced, biologically-influenced or purely abiotic processes, or a combination of all. The aim of this research is to advance knowledge on the formation of carbonates precipitated (or diagenetically altered) in extreme, continental environments by studying biotic versus abiotic mechanisms of crystallization, and to contribute to the astrobiology debate around terrestrial analogues of Martian extreme environments. Both fossil (upper Pleistocene to Holocene) and active carbonate spring mounds from the Great Artesian Basin (South Australia) have been investigated. These carbonates consist of low-Mg to high-Mg calcite tufa. Four facies have been described: (i) carbonate mudstone/wackestone; (ii) phytohermal framestone/boundstone; (iii) micrite boundstone; and (iv) coarsely crystalline boundstone. The presence of filaments encrusted by micrite, rich in organic compounds, including ultraviolet-protectants, in phytohermal framestone/boundstone and micrite boundstone is clear evidence of the existence of microbial mats at the time of deposition. In contrast, peloidal micrite, despite commonly being considered a microbial precipitate, is not directly associated with filaments in the Great Artesian Basin mounds. It has probably formed from nanocrystal aggregation on colloid particulate. Thus, where biofilms have been documented, it is likely that bacteria catalyzed the development of fabrics. It is less certain that microbes induced calcium carbonate precipitation elsewhere. Trace elements, including rare earth element distribution from laminated facies, highlight strongly evaporative settings (for example, high Li contents). Carbon dioxide degassing and evaporation are two of the main drivers for an increase in fluid alkalinity, resulting in precipitation of carbonates. Hence, although the growth of certain fabrics is fostered by the presence of microbial mats, the formation of carbonate crystals might be independent from it and mainly driven by extrinsic factors. More generally, biological processes may be responsible for fabric and facies development in micritic boundstone whilst micrite nucleation and growth are driven by abiotic factors. Non-classical crystallization pathways (aggregation and fusion of nanoparticles from nucleation clusters) may be more common than previously thought in spring carbonate and this should be carefully considered to avoid misinterpretation of certain fabrics as by-products of life. It is proposed here that the term ‘organic-compound catalyzed mineralization’ should be used for crystal growth in the presence of organic compounds when dealing with astrobiological problems. This term would account for the possibility of multiple crystallization pathways (including non-classical crystallization) that occurred directly from an aqueous solution without the direct influence of microbial mats.     

塔里木盆地柯坪地区奥陶系鹰山组台内滩沉积特征

通过对柯坪地区蓬莱坝剖面奥陶系鹰山组的野外实测可以将其划分为下、中、上三段,每段都具有不同的相序结构和沉积特征,下段主要以含陆源泥质的泥晶粗砂屑灰岩为主,中段为亮晶粉-细砂屑灰岩和层纹石灰岩互层出现,上段主要为中-厚层状似球粒泥晶灰岩,台内颗粒滩主要发育在中、下两段;柯坪水泥厂剖面也可以划分为三段,但界限没有蓬莱坝剖面明显,主体表现为中层状的亮晶砂屑灰岩和泥晶砂屑灰岩交互出现。通过对蓬莱坝剖面和柯坪水泥厂剖面的岩石进行野外露头、偏光显微镜、扫描电镜等不同尺度的观测及沉积微相分析,理清了柯坪地区鹰山组的岩石类型和相序结构,建立了柯坪地区颗粒滩沉积模式:由于水体深度和能量的差异,柯坪地区发育了四种相带类型--高能颗粒滩相带、滩间洼地沉积相带、低能颗粒滩相带、开阔浅海沉积相带。中-低能颗粒滩相带主要发育泥晶中-粗砂屑颗粒滩,高能颗粒滩相带主要发育亮晶细-中砂屑颗粒滩,并且两种颗粒滩都可以划分出3种亚相--滩主体、滩翼和滩内洼地;在微生物主导的碳酸盐建造向后生动物主导的碳酸盐岩建造转换的地质背景下,柯坪地区在奥陶系鹰山组沉积时期总体处于大面积发育微生物似球粒的浅水环境,沉积物的形成与改造受微生物活动的影响,微生物作用一方面为颗粒滩的发育提供了良好的物质基础,另一方面也控制了该时期颗粒滩的沉积特征。     

鲕粒滩中光合作用生物膜构建的高能核形石:以辽西葫芦岛三道沟剖面寒武系张夏组为例

核形石是一种具有双重属性而较为特别的微生物碳酸盐岩:①作为一种包覆颗粒类型,核形石以不平滑的圈层和较大的大小被解释为微生物成因区别于成因存在着较大争议的鲕粒;②作为一种形成在围绕着核心的序列式纹层化作用过程中的球形或椭球型的生物沉积构造,核形石还常常被解释为微生物碳酸盐岩的一种类型而被归为球状叠层石。在辽西葫芦岛三道沟剖面寒武系苗岭统张夏组顶部的块状鲕粒滩相灰岩之中,密集发育着厘米级别大小的高能泥晶核形石。另外,以下重要特征将张夏组鲕粒灰岩中的核形石特征化,包括:①厘米级别的大小;②椭圆形为主的形态学特征;③特征性的纹层状构造;④核形石皮层中普遍发育而且较高密度保存的丝状蓝细菌鞘的钙化化石等等。尽管穿越成岩作用过滤器去解释古代核形石复杂的形成机理将存在着巨大的挑战,也尽管形成这些核形石复杂的生物膜钙化作用机理还没有得到精确的了解,但是,辽西葫芦岛三道沟剖面张夏组中的核形石,直接的微生物化石证据,尤其是在核形石内较为丰富的丝状蓝细菌鞘化石,使其成为一个了解光合作用生物膜建造核形石的典型实例;同时,也为进一步了解形成在水柱中的放射鲕粒以及形成在海底的泥晶核形石之间复杂的形成机理的差异性,提供了一个较为典型的实例。     

四川甘溪泥盆系观雾山组白云岩特征与其形成条件的关系(英文)

本文通过沉积环境分析,X射线衍射、扫描电镜、同位素及阴极发光分析,讨论了甘溪泥盆系观雾山组白云石的晶体形态及大小、有序度、碳酸钙克分子含量,同位素特征及阴极发光特征与形成条件的关系。中晶白云岩及细晶白云岩分别产于生物层及潮坪环境,为成岩早期地下淡水与海水混合白云岩化作用的产物。低的碳酸钙克分子含量,中-弱的阴极发光强度及低的δ18O、δ13C值。微晶白云岩形成于泻湖环境。白云石具他形粒状晶,差的有序度,高的碳酸钙克分子含量,强的阴极发光强度及高的δ18O、δ13C值,为准同生期高Mg2+/Ca2+值卤水交代碳酸钙软泥形成。     

World's largest known Precambrian fossil black smoker chimneys and associated microbial vent communities, North China: Implications for early life

Black smoker chimneys and biological vent communities have been identified at many sites on the deep seafloor, particularly along oceanic spreading centers. We report the largest and oldest known, microbe-rich sub-meter-sized black smoker chimneys and mounds from a 1.43 billion-year old sulfide deposit in a continental graben in northern China. These chimneys are especially well preserved, with characteristic morphology, internal textures and internal cylindrical mineralogical zonation. Four main types of chimneys are distinguished on textural and mineralogical criteria, exhibiting either Zn–Fe-sulfide or Pb–Zn–Fe-sulfide internal cylindrical mineralogical zones. The chimneys mark vent sites in submarine grabens indicating focused flow-venting processes. The fossil chimneys have mineralogical and geological evolutionary features similar to their counterparts on the modern seafloor and other submarine hydrothermal vents. Black smoker vent fluids and seafloor tectonism played important roles for formation of the massive sulfide deposits in the Mesoproterozoic.We also report the first known, remarkably diverse assemblage of fossil microbialites from around and inside Precambrian vent chimneys, demonstrating that Proterozoic life flourished around submarine hot vents and deep within the chimney vent passages. Filamentous, spherical, rod, and coccus-shaped fossil microbes are preserved preferentially on sulfide precipitates. Based on the depth and setting of the fossil biota, the organisms that produced the microbialites were likely sulfate-reducing chemosynthetic and thermophyllic microbes. Textural and mineralogical evidence shows that biomineralization processes enhanced chimney growth and sulfide precipitation.Close association of microorganisms with sulfide chimneys in modern deep-sea hydrothermal vents and younger ophiolites has sparked speculation about whether life may have originated at similar vents. However, little is known about fossil equivalents of vent microfossils and black smoker chimneys from Earth's early evolution. The fossilized microorganisms from the Gaobanhe black smoker chimney sulfide deposits include thread-like filaments with branching and twisted forms and preserved organic carbon, representing fossilized remnants of microbial mats metabolized at high temperatures characteristic of venting fluids. The preservation of fossil microorganisms provides evidence that microbial populations were closely associated with black smoker chimneys in Earth's early history. The microbial population clearly constitutes the site for mediating mineral formation. These ancient microbial fossils lead to a much better understanding of early life on the deep seafloor. The discovery of the Mesoproterozoic microfossils within black-smoker hydrothermal chimneys indicates that hydrothermal activity around sea-floor vents supported dense microbial communities, and supports speculation that vent sites may have hosted the origin of life.     

湘西—黔东地区寒武系清虚洞组地层特征与铅锌成矿关系

湘西—黔东地区寒武系发育完整,是一套从黑色岩系到碳酸盐岩的沉积序列。下寒武统清虚洞组由灰岩段和白云岩段组成,纵向上构成总体向上海水变浅的沉积相序列,同时反映了缓坡型碳酸盐岩台地的发育过程。该组空间上从北西至南东可识别出潮坪相、局限台地相粉细晶云岩、台地边缘浅滩相粉细晶灰岩和台地边缘(滩)丘相微晶灰岩、浅-深缓坡相、陆棚相泥灰岩、台地前缘盆地等沉积。研究表明,地层岩性、岩相古地理对铅锌矿具有明显的控制作用,微晶丘是主要容矿层,与微生物和海底热水关系密切。铅锌成矿明显与浊流沉积和风暴沉积等事件沉积相关,浊积岩、微晶丘、砾(粒)屑灰岩构成一完整的铅锌控矿序列。     

Composite Stratigraphy of the Sailinhudong Group and Ore-bearing Micrite Mounds in the Bayan Obo Deposits,Inner Mongolia,China

Based on studies of sequence stratigraphy, event stratigraphy, biostratigraphy and lithostratigraphy, it is concluded that the Sailinhudong Group is a part of the Bayan Obo Group. Some trilobite fragments are first found in thin sections of the rock from the lower part of the Sailinhudong Group and some Ordovician acritarchs and chitinozoans are also found in this group. A formationa unit of carbonate seismites is first recognized in the upper part and a huge micrite mound is first identified at the top. Dolomite, the host rock of the super giant Bayan Obo Fe-Nb-REE deposits, is neither an igneous carbonatite nor a common bedded sedimentary carbonate, but a huge micrite mound. It has the same macroscopic characters as the micrite mounds at the top of the Sailinhudong Group, which suggests that they should be of the same horizon. According to the fossils, the Sailinhudong and Bayan Obo Groups should be of the Early Palaeozoic rather than the Middle Proterozoic. The new discovery and new idea will throw l     

柴达木盆地西部地区古近系及新近系碳酸盐岩沉积相

柴达木盆地西部地区古近系和新近系湖相碳酸盐岩主要分布于下干柴沟组上段到油砂山组,其中,下干柴沟组上段和上干柴沟组的碳酸盐岩更发育。碳酸盐岩主要岩石类型有泥晶灰岩、藻灰岩和颗粒灰岩等三大类,此外,还普遍发育由石灰质、白云质和陆源碎屑等3种组分构成的混积岩。碳酸盐岩沉积相可划分为滨湖灰泥坪、滨湖藻坪、浅湖颗粒滩、浅湖藻丘以及半深湖泥灰岩相。滨湖灰泥坪的主要岩石类型有泥晶灰岩、含陆屑泥晶灰岩、陆屑泥晶灰岩以及陆屑泥灰岩等;滨湖藻坪为藻泥晶灰岩、藻纹层灰岩、含陆屑藻泥晶灰岩;浅湖颗粒滩有亮晶或泥微晶的鲕粒灰岩、生屑灰岩和内碎屑灰岩,其次为含陆屑颗粒灰岩;浅湖藻丘为藻叠层灰岩、藻团块灰岩、藻泥晶灰岩和含陆屑藻泥晶灰岩;而半深湖泥灰岩相的主要岩石类型为泥晶灰岩、泥灰岩以及含少量陆屑泥和粉砂的泥晶灰岩或泥灰岩。碳酸盐岩沉积相表现出很强的由西南向东北的迁移性。