Influence of topsoil of pyroclastic origin on microbial contamination of groundwater in fractured carbonate aquifers

The aim of the research was to analyse the influence of a topsoil of pyroclastic origin on microbial contamination of groundwater in a carbonate aquifer and verify the reliability of thermotolerant coliforms and fecal enterococci as bacterial indicators. The research was carried out through hydrogeological and microbiological monitoring at an experimental field site in Italy during two hydrologic years and through column tests in a laboratory. The taxonomic classification of fecal indicators detected in spring water samples was performed using API20 galleries. Fecal enterococci were also identified by means of 16S rRNA gene sequencing. The topsoil of pyroclastic origin significantly retains both thermotolerant coliforms and fecal enterococci. Results of column tests carried out in soil blocks collected randomly within the test site suggest that Escherichia coli was more retained than Enterococcus faecalis, even though this difference is statistically significant in only two out of six soil samples. Thus, a non-uniform difference in retention is expected at field scale. This suggestion is in agreement with the results of the microbiological monitoring. In fact, fecal enterococci were a more reliable indicator than thermotolerant coliforms for detecting contamination at both seasonal springs of the aquifer system, while no significant differences were observed at the perennial spring.     

Processes of carbonate precipitation in modern microbial mats

Microbial mats are ecosystems that arguably greatly affected the conditions of the biosphere on Earth through geological time. These laminated organosedimentary systems, which date back to > 3.4 Ga bp, are characterized by high metabolic rates, and coupled to this, rapid cycling of major elements on very small (mm-µm) scales. The activity of the mat communities has changed Earth's redox conditions (i.e. oxidation state) through oxygen and hydrogen production. Interpretation of fossil microbial mats and their potential role in alteration of the Earth's geochemical environment is challenging because these mats are generally not well preserved.Preservation of microbial mats in the fossil record can be enhanced through carbonate precipitation, resulting in the formation of lithified mats, or microbialites. Several types of microbially-mediated mineralization can be distinguished, including biologically-induced and biologically influenced mineralization. Biologically-induced mineralization results from the interaction between biological activity and the environment. Biologically-influenced mineralization is defined as passive mineralization of organic matter (biogenic or abiogenic in origin), whose properties influence crystal morphology and composition. We propose to use the term organomineralization sensu lato as an umbrella term encompassing biologically influenced and biologically induced mineralization. Key components of organomineralization sensu lato are the “alkalinity” engine (microbial metabolism and environmental conditions impacting the calcium carbonate saturation index) and an organic matrix comprised of extracellular polymeric substances (EPS), which may provide a template for carbonate nucleation. Here we review the specific role of microbes and the EPS matrix in various mineralization processes and discuss examples of modern aquatic (freshwater, marine and hypersaline) and terrestrial microbialites.     

Petrology of Lower Cretaceous carbonate mud mounds (Albian, N. Spain): insights into organomineralic deposits of the geological record

The process of organomineralization is increasingly well understood with respect to modern carbonate sediments accumulating adjacent to tropical reef atolls and reef caves. Mineralization related to non-living organic substrates results in autochthonous micrite production (‘automicrites’). ‘Automicrites’ are the main constructive element of Lower Cretaceous (Albian) carbonate mud mounds in northern Spain. These slope mud mounds occur within transgressive and early highstand system tracts encompassing several macrobenthic ecological zones. They are clearly separated from the biocalcifying carbonate factory (Urgonian carbonate platforms), in both space and time. Within these build-ups, most ‘automicrites’ were initially indurated and accreted to form a medium-relief growth framework. ‘Automicrites’ have a uniform, presumably high-Mg-calcite precursor mineralogy. They show an inorganic stable-isotope signature (?¹³C around +3·3‰) within the range of early marine cements, and skeletal compounds lacking major vital effects. Epifluorescence microscopy shows that they have facies-specific fluorescence, which is similar to skeletal compounds of Acanthochaetetes, but clearly different from allomicritic sediment and cements, which are mostly non-fluorescent. The EDTA-soluble intracrystalline organic fraction (SIOF) of Albian automicrites shows an amino acid spectrum that is similar to shallow subsurface samples from their modern counterparts. Gel electrophoresis of the SIOF demonstrates an exclusively acidic character, and a mean molecular size range between 20 and 30 kDa. Experiments in vitro (inhibition tests) indicate that the SIOF has a significant Ca²⁺-binding capacity. Fluorescence and chemical characteristics of SIOF point to a main substance class, such as humic and fulvic acids, compounds that form from pristine organic matter during early diagenesis. Biomarker analyses provide evidence for the crucial role of biodegradation by heterotrophic microorganisms, but no biomarker for cyanobacteria has been found. Primary sources of organic material should have been manifold, including major contributions by metazoans such as sponges. It is concluded that many carbonate mud mounds are essentially organomineralic in origin and that the resulting fabric of polygenetic muds (‘polymuds’) may represent ancestral metazoan reef ecosystems, which possibly originated during the Neoproterozoic.     

塔里木盆地奥陶系碳酸盐岩岩溶分类、期次及勘探思路

奥陶系海相碳酸盐岩已成为塔里木盆地最重要的勘探开发层系,岩溶作用则是形成优质碳酸盐岩储集层的关键因素之一。针对塔里木盆地碳酸盐岩岩溶分类方案不统一、岩溶术语界定不清楚、生产应用难度大的现状,作者分析了奥陶系不同地区、不同层位、不同时期岩溶储集层特征及岩溶发育程度的差异性,依据岩溶成因及主控因素提出了塔里木盆地奥陶系碳酸盐岩岩溶分类,划分出风化岩溶、礁滩体岩溶和埋藏岩溶3大类,其中风化岩溶又分为潜山岩溶和层间岩溶2个亚类。研究指出礁滩体岩溶、层间岩溶、潜山岩溶是塔里木盆地的重要勘探岩溶类型,并以构造运动为主线将奥陶系岩溶划分为5期,开展了不同类型岩溶特征及分布规律研究,指出了3种重要类型岩溶的勘探思路。此次研究统一了塔里木盆地奥陶系岩溶分类及期次,对勘探开发生产和研究工作具有较强的指导性,具有重要的理论指导及实践应用意义。     

Morphology and environment of cold-water coral carbonate mounds on the NW European margin

Cold-water coral carbonate mounds, owing their presence mainly to the framework building coral Lophelia pertusa and the activity of associated organisms, are common along the European margin with their spatial distribution allowing them to be divided into a number of mound provinces. Variation in mound attributes are explored via a series of case studies on mound provinces that have been the most intensely investigated: Belgica, Hovland, Pelagia, Logachev and Norwegian Mounds. Morphological variation between mound provinces is discussed under the premise that mound morphology is an expression of the environmental conditions under which mounds are initiated and grow. Cold-water coral carbonate mounds can be divided into those exhibiting “inherited” morphologies (where mound morphology reflects the morphology of the colonised features) and “developed” morphology (where the mounds assume their own gross morphology mainly reflecting dominant hydrodynamic controls). Finer-scale, surface morphological features mainly reflecting biological growth forms are also discussed.     

碳酸盐岩地区水质和化学动力学模型研究

本文描述了在碳酸盐岩分布的水文地质系统内,怎样利用水质相对,绝对含量,运用化学热力学、化学动力学和水动力学的理论及方法,进行半定量或定量的确定研究区某些水文地质信息,具有重要的理论和实际意义。 文章就系统水文地球化学类型分带模型和成因;系绕水化学分带溶蚀特征的定量评价;以及定量评价水文地质条件的化学动力学法等三个方面展开讨论。理论和计算在山东、河北、山西等省区某些水文地层系统中运用时,获得与实际水文地质特点相吻合的效果。     

扬子地区晚奥陶世碳酸盐台地淹没事件及其地质意义

碳酸盐岩台地广泛发育及其淹没事件是扬子地区晚奥陶世地层的重要特征之一.基于岩石学、沉积学特征和古生物资料等对扬子地区晚奥陶世碳酸盐岩台地沉积演化、淹没事件及其油气地质意义进行了分析.结果表明:扬子地区晚奥陶世沉积演化分为宝塔一临湘期碳酸盐台地沉积和五峰期深水、浅水陆棚沉积两个阶段;淹没事件开始于五峰初期,主要受控于构造...     

断裂对碳酸盐岩地层储集空间的影响——以塔里木盆地轮古东地区奥陶系碳酸盐岩地层为例

轮古东地区主要发育两期断裂,断裂使碳酸盐岩地层形成了以大型溶洞占主导,网状构造裂缝和孔洞相辅的溶洞裂缝储集空间体系。早期断裂主要控制了瘤状灰岩尖灭线西北的潜山高地岩溶,形成深切峡谷式沟壑相连的古地貌,流体溶蚀裂缝形成溶洞为主的储集空间。晚期断裂一方面形成新的储集空间并将早期形成的未充填或半充填的裂缝和溶蚀孔洞沟通;另一方面,为大气淡水进入下部岩层提供了通道,形成在奥陶系下部地层发育的水平潜流带和深部缓流带岩溶体系。此外,火山热液沿两期断裂进入碳酸盐岩地层,对通道附近的碳酸盐岩产生显著的溶蚀,主导了深部的岩溶作用。     

External controls on the distribution,fabrics and mineralization of modern microbial mats in a coastal hypersaline lagoon,Cayo Coco (Cuba)

Active, carbonate‐mineralizing microbial mats flourish in a tropical, highly evaporative, marine‐fed lagoonal network to the south of Cayo Coco Island (Cuba). Hypersaline conditions support the development of a complex sedimentary microbial ecosystem with diverse morphologies, a variable intensity of mineralization and a potential for preservation. In this study, the role of intrinsic (i.e. microbial) and extrinsic (i.e. physicochemical) controls on microbial mat development, mineralization and preservation was investigated. The network consists of lagoons, forming in the interdune depressions of a Pleistocene aeolian substratum; they developed due to a progressive increase in sea‐level since the Holocene. The hydrological budget in the Cayo Coco lagoonal network changes from west to east, increasing the salinity. This change progressively excludes grazers and increases the saturation index of carbonate minerals, favouring the development and mineralization of microbial mats in the easternmost lagoons. Detailed mapping of the easternmost lagoon shows four zones with different flooding regimes. The microbial activity in the mats was recorded using light–dark shifts in conjunction with microelectrode O₂ and HS^? profiles. High rates of O₂ production and consumption, in addition to substantial amounts of exopolymeric substances, are indicative of a potentially strong intrinsic control on mineralization. Seasonal, climate‐driven water fluctuations are key for mat development, mineralization, morphology and distribution. Microbial mats show no mineralization in the permanently submersed zone, and moderate mineralization in zones with alternating immersion and exposure. It is suggested that mineralization is also driven by water‐level fluctuations and evaporation. Mineralized mats are laminated and consist of alternating trapping and binding of grains and microbially induced magnesium calcite and dolomite precipitation. The macrofabrics of the mats evolve from early colonizing Flat mats to complex Cerebroid or Terrace structures. The macrofabrics are influenced by the hydrodynamic regime: wind‐driven waves inducing relief terraces in windward areas and flat morphologies on the leeward side of the lagoon. Other external drivers include: (i) storm events that either promote (for example, by bioclasts covering) or prevent (for example, by causing erosion) microbial mat preservation; and (ii) subsurface degassing, through mangrove roots and desiccation cracks covered by Flat mats (i.e. forming Hemispheroids and Cerebroidal structures). These findings provide in‐depth insights into understanding fossil microbialite morphologies that formed in lagoonal settings.     

石英阴极发光在火成岩研究中的应用

阴极发光是一种研究火成岩石英显微生长结构的有效技术方法。文章以甲玛斑岩铜矿床中岩体样品分析为例,简要介绍了光学显微镜阴极发光(OM-CL)和扫描电镜阴极发光(SEM-CL)两种图片的特点,并综述了石英阴极发光在火成岩研究中的应用。阴极发光所显示出的火成岩石英中的生长形式和蚀变结构反映了岩浆的结晶历史。相对稳定的以蓝色阴极发光为主的斑晶区域主要与石英中Ti含量的变化有关,它反映了结晶作用的温度。由于在岩浆演化过程中,与铝、锂、钾、锗、硼、铁、磷相比,钛更加相容,因此随着岩浆分异程度的加深,火成岩中铝/钛逐渐升高。石英阴极发光不仅能显示岩浆早期及岩浆晚期的各种结构,如生长环带、重熔表面、溶蚀湾等,还反映了许多次生结构,如显微裂隙等。这些现象在光学显微镜下难以观察区分。晶体的显微结构提供了熔体来源和演化的重要信息。将石英结构和熔融包裹体与微量元素研究相结合反映了岩浆演化详细的PTt轨迹,它是富硅酸盐岩浆演化过程中物理-化学条件改变的敏感指示剂。     

岩溶作用对沙雅隆起奥陶系碳酸盐岩储集层的控制作用

沙雅隆起经历了多期构造活动和长期岩溶作用的改造,形成分布极不均匀的裂缝、孔洞系统,构成了奥陶系碳酸盐岩储层的主要储集空间,在沙雅隆起奥陶系碳酸盐岩地层沉积、成岩之后,经历了加里东期—印支期—燕山期多次构造抬升、暴露、剥蚀和岩溶作用,形成了区内广泛分布的风化壳型岩溶作用。研究区至少发育4期岩溶作用,即加里东中晚期,海西早期,海西晚期和印支期—燕山期,其中海西早期和海西晚期是岩溶发育的主要时期。岩溶作用对奥陶系碳酸盐岩储层的形成和分布具有重要的控制作用,其储层发育层段限制在岩溶作用影响深度范围内。     

中国西部三大盆地海相碳酸盐岩台地边缘类型及特征

在回顾经典的碳酸盐沉积模式类型研究和我国学者对碳酸盐岩台地边缘特征研究的基础上,以构造控盆、盆地控相、相控生储盖组合为指导思想,依据中国西部三大海相盆地碳酸盐岩发育的特殊性,从中国西部三大盆地海相碳酸盐岩发育特征和地质实际情况出发,系统建立了5种碳酸盐岩台地边缘类型及沉积模式和12种亚类类型。以中国西部三大盆地不同时期发育的碳酸盐沉积特征为主线,从盆地构造演化、岩性特征、相带变化以及模式演化等方面详细分析了各个碳酸盐岩台地边缘类型及沉积模式特征。不同类型台地边缘及其沉积模式演化特征研究对分析生烃、储烃和盖烃物质等油气要素的时间和空间匹配关系具有重要的指导意义。     

鄂尔多斯盆地奥陶系丘形反射的解释及其与礁的关系

鄂尔多斯盆地Ｔ９－Ｔ１０地震反射波组之间的奥陶系碳酸盐岩中存在着许多丘形反射,其中一部分属于以藻类生物为主的藻丘类型,一部分为东部盐凹中的盐丘,一部分为奥陶系顶古风化壳残丘,其它丘形反射为绕射波,回转波,或者为地表静校不当引起的假象,奥陶系的礁丘一般规模很小,岩性以粘结为主,其孔隙发育好坏同风化残丘一样,主要取决于次生溶蚀作用,但礁丘生长过程中由于受海面波动影响,曾发生过多次暴露,形成多期溶孔,礁     

塔中西部奥陶系鹰山组古岩溶特征及主控因素

为明确塔中西部奥陶系鹰山组古岩溶储层发育及主控因素,总结鹰山组古岩溶特征及发育条件,划分了岩溶层组类型。在鹰山组古地貌恢复基础上,通过钻井、取心、测井等资料,分析丘状岩溶台地、上丘状岩溶缓坡地和下丘状岩溶缓坡地典型井岩溶缝洞特征。结合大量钻井资料分析了上述3类古地貌单元岩溶缝洞储层发育规律及主控因素。对岩溶缝洞储层发育深度分析表明,岩溶缝洞发育段主要在鹰山组顶面以下0~180 m,受3期海平面控制,发育多层缝洞。表层溶洞主要发育在0~50 m,泥质充填较强,测井GR值较高,溶洞规模多小于2 m。岩溶台地区岩溶缝洞形成受微地貌、水动力条件控制,以小规模溶洞、溶蚀孔洞、溶蚀裂缝为主,缝洞后期易充填。岩溶缓坡地岩溶缝洞形成受岩溶层组、水动力条件控制,以小溶蚀孔洞、溶蚀裂缝为主,后期不易充填。滨岸岩溶带及岩溶岛屿发育海水、混合水岩溶作用,溶蚀作用及冲蚀、侵蚀作用使该区域形成较大洞穴。     

The impacts of pasture- and manure-spreading on microbial groundwater quality in carbonate aquifers

Hydrogeological and microbiological research is in progress to analyze the interaction between groundwater and microbial pollutants, produced by pasture and/or manure spreading, in the areas of different carbonate aquifers of southern Italy. Several springs and wells were studied, and the precipitation, the discharge, the groundwater level and the classic microbial indicators of pollution were monitored weekly or daily. The experimental results show that the pasture and the manure spreading produced microbial contamination of the groundwater, even if runoff infiltration in swallow holes does not exist. The time dependence of microbial contamination shows a series of peaks irregularly distributed, related to the precipitation that produce effective infiltration.     

塔河油田上奥陶统良里塔格组碳酸盐岩沉积地球化学特征与台地演化

塔河油田上奥陶统良里塔格组下段以泥微晶灰岩、瘤状灰岩为主,上段以鲕粒灰岩、生屑灰岩、砂砾屑灰岩为主,纵向上构成了一个向上水体变浅的沉积序列。根据层序地层学研究结果,将良里塔格组划分为一个三级层序,细分为两个体系域。通过对各体系域地层单元的岩相学和地球化学分析研究,恢复了各时期的古地理面貌及沉积相带的空间展布。最终研究结果表明良里塔格组沉积相带具有开阔台地、台地边缘和斜坡3种类型,平面上由北向南顺序展布,走向近东西。微量元素分析进一步佐证和完善了该区沉积相带分析,V、Ni和Cr微量元素的含量显示从浅水到深水总体呈增加之势,Ce异常曲线对沉积环境也有良好反映,而台地边缘相的Sr/Ba比值表现出异常高值。     

Contribution of carbonate rock weathering to the atmospheric CO2 sink

To accurately predict future CO₂ levels in the atmosphere, which is crucial in predicting global climate change, the sources and sinks of the atmospheric CO₂ and their change over time must be determined. In this paper, some typical cases are examined using published and unpublished data. Firstly, the sensitivity of carbonate rock weathering (including the effects by both dissolution and reprecipitation of carbonate) to the change of soil CO₂ and runoff will be discussed, and then the net amount of CO₂ removed from the atmosphere in the carbonate rock areas of mainland China and the world will be determined by the hydrochem-discharge and carbonate-rock-tablet methods, to obtain an estimate of the contribution of carbonate rock weathering to the atmospheric CO₂ sink. These contributions are about 0.018 billion metric tons of carbon/a and 0.11 billion metric tons of carbon/a for China and the world, respectively. Further, by the DBL (Diffusion Boundary Layer)-model calculation, the potential CO₂ sink by carbonate rock dissolution is estimated to be 0.41 billion metric tons of carbon/a for the world. Therefore, the potential CO₂ source by carbonate reprecipitation is 0.3 billion metric tons of carbon/a. Received: 12 May 1999 · Accepted: 16 August 1999     

塔中地区奥陶系碳酸盐岩埋藏溶蚀特征及初步预测

塔中地区奥陶系碳酸盐岩发育多种形式岩溶作用,其中埋藏溶蚀是形成有利储层的重要机制之一.录井岩心分析化验资料及宏观地质背景分析表明,塔中地区奥陶系碳酸盐岩主要发育4期埋藏溶蚀,其中Ⅰ、Ⅱ期溶蚀孔洞基本已被充填,Ⅲ期残留部分孔隙和Ⅳ期溶蚀孔洞为现今储层有效储集空间.上奥陶统良里塔格组现今未被充填的粒内溶孔及铸模孔可能主要形成于埋藏溶蚀,并非准同生溶蚀.埋藏溶蚀发生的流体介质主要为有机质演化过程中形成的有机酸和CO2,在更深部或经历更高热史经历的区域,H2S对储层的形成可能会有较大贡献,热水-热液溶蚀对储集空间贡献有限.初步分析表明,卡塔克隆起西北部埋藏溶蚀孔隙较发育,塔中南部台地边缘带可能是埋藏溶蚀另一相对较发育地区.     

鄂尔多斯盆地中奥陶统马家沟组海相碳酸盐岩储集层特征*

探讨了鄂尔多斯盆地中奥陶统马家沟组海相碳酸盐岩储集层岩石物理相特征及储集层分类方法。应用露头、岩心、薄片分析及储集层物性测试及压汞实验方法开展了碳酸盐岩储集层岩性、孔隙结构及物性研究,应用储集层流动带指标FZI开展了储集层岩石物理相特征及储集层分类方法研究。马家沟组碳酸盐岩储集层岩石类型主要为岩溶角砾泥晶—粉晶白云岩、膏盐溶蚀角砾泥晶—粉晶白云岩、含膏盐或膏盐质白云岩、粉晶—细晶白云岩、残余结构中晶—细晶及粗晶—中晶白云岩、次生灰岩、泥晶灰岩及白云岩,发育洞穴、溶洞、孔隙及裂缝4种储集空间,主要发育晶间孔型、裂缝型、裂缝—晶间孔型、裂缝—晶间孔—溶洞型4类储渗类型。依据流动带指标将储集层划分为6类岩石物理相及24类亚相,据此将储集层分为5类7亚类：一类储集层是天然气赋存的优质储集层,主要分布于马五₁、马五₄及马五₆段;二、三类储集层是马家沟组主要储集层类型,以孔隙为主的二₁、三₁类储集层主要分布于马五₁—马五₆段,以裂缝为主的二₂、三₂类储集层主要分布于马四段;四类储集层物性差,见于各段;五类为非储集层。研究结果表明,基于岩石物理相的储集层研究方法是揭示碳酸盐岩储集层特征及开展储集层定量分类与评价的有效途径。     

Facies and evolution of the carbonate factory during the Permian–Triassic crisis in South Tibet,China

The nature of Phanerozoic carbonate factories is strongly controlled by the composition of carbonate‐producing faunas. During the Permian–Triassic mass extinction interval there was a major change in tropical shallow platform facies: Upper Permian bioclastic limestones are characterized by benthic communities with significant richness, for example, calcareous algae, fusulinids, brachiopods, corals, molluscs and sponges, while lowermost Triassic carbonates shift to dolomicrite‐dominated and bacteria‐dominated microbialites in the immediate aftermath of the Permian–Triassic mass extinction. However, the spatial–temporal pattern of carbonates distribution in high latitude regions in response to the Permian–Triassic mass extinction has received little attention. Facies and evolutionary patterns of a carbonate factory from the northern margin of peri‐Gondwana (palaeolatitude ca 40°S) are presented here based on four Permian–Triassic boundary sections that span proximal, inner to distal, and outer ramp settings from South Tibet. The results show that a cool‐water bryozoan‐dominated and echinoderm‐dominated carbonate ramp developed in the Late Permian in South Tibet. This was replaced abruptly, immediately after the Permian–Triassic mass extinction, by a benthic automicrite factory with minor amounts of calcifying metazoans developed in an inner/middle ramp setting, accompanied by transient subaerial exposure. Subsequently, an extensive homoclinal carbonate ramp developed in South Tibet in the Early Triassic, which mainly consists of homogenous dolomitic lime mudstone/wackestone that lacks evidence of metazoan frame‐builders. The sudden transition from a cool‐water, heterozoan dominated carbonate ramp to a warm‐water, metazoan‐free, homoclinal carbonate ramp following the Permian–Triassic mass extinction was the result of the combination of the loss of metazoan reef/mound builders, rapid sea‐level changes across Permian–Triassic mass extinction and profound global warming during the Early Triassic.