论岷山地区冰缘岩溶

岷山地区冰缘岩溶是处于岷山雪线下部冰缘环境的碳酸盐岩之溶蚀与冻融相互渗合、叠加的岩溶地质类型,具有碳酸盐岩溶场和冰缘岩屑与冰期、间冰期堆积物岩溶场的二元结构。岷山地区大多数碳酸盐岩处于较低的海拔区,在第四纪气温振荡回暖的影响下冰缘岩溶已经衰退,仅残留着早期冰缘岩溶形成的地貌和钙华体,现在的黄龙沟冰缘岩溶因其碳酸盐岩海拔高,仍处在第四纪末期冰川退缩后的冰缘环境,冰缘岩溶地貌和钙华体还在发育,不过现今全球性气温升高和人类的活动对冰缘岩溶都将产生负面影响,以钙华体为核心景观的黄龙、九寨沟风景区的管理部门应予加强监测和保护。     

钙华天然海绵地质体多孔特性及其对水循环调节意义——以四川黄龙为例

四川黄龙自然遗产点以钙华景观闻名海内外,其钙华体多孔性地质结构,使钙华地质体具备"海绵"特性。本文通过电子扫描显微镜(SEM)和探地雷达、电磁法等地质探测技术对钙华地质体的多孔性质和水循环特性进行研究,并结合多年现场踏勘经验探讨了钙华地质体的多孔性质对水循环的调节意义。分析结果显示,黄龙钙华体经过地质作用形成了不同尺度的孔隙结构,其中生物参与形成的微观孔道具备"渗透、净化"功能;侵蚀作用产生的可视孔洞、缝隙快速透水,并进一步发育成塌陷区和钙华漏斗。彩池、溶洞和裂缝为水体储蓄和运移提供很好通道和场所,地质探测分析表明典型钙华段地下腔体具备"蓄水、排水"功能。各尺度孔隙互相影响,共同调节黄龙景区内的地表-地下水循环系统。初步研究发现,藻类在黄龙钙华沉积过程中具有加速和减少孔隙形成的双向调控作用,未来将结合藻类在钙华构筑过程的作用,继续深化黄龙钙华地质体的孔隙结构性质研究,为钙华景观的维护和保育提供参考。     

雪宝顶流域黄龙“8·8”地震后短期内主要水环境变化特征

富含Ca2+ 和HCO3-的水体是黄龙钙华地貌得以持续沉积的首要条件。为明确2017年九寨沟“8·8”地震是否对黄龙脆弱钙华体产生影响并进而导致水环境的改变,于2017年10月和2018年8月对黄龙3个主要监测点进行了水样采集和水质参数检测。通过主成分分析震前的多次水质检测结果,得到影响黄龙水化学的主要参数,并与震后的水化学参数进行对比分析,发现:2016年（震前）水质参数显示pH、总磷、总氮对黄龙水质起主要贡献作用,地震后水体的pH、Ca2+ 和HCO3-含量上升,而总磷含量则下降较多,表明地震对黄龙钙华体内部结构产生了影响,导致上升泉（转花泉）中的Ca2+ 和HCO3- 含量增加,并影响了pH,而震后水体中的总磷含量减少,这可能与游客数量大幅度减少有关;“8·8”地震对黄龙钙华沉积区水环境造成了影响,并有利于钙华沉积。      

世界自然遗产-四川黄龙钙华景观的形成与演化

本文对作者十余年来在四川黄龙(世界遗产地)的钙华研究成果和最新的一些监测发现进行了综述, 目的是为公众更好地了解黄龙、保护黄龙提供科学基础。主要结果和结论是: (1)黄龙钙华的形成是由于地球深部高分压的CO2在碳酸盐岩补给区产生富含碳酸氢钙的地下水, 当其以泉的形式出露地表时, 由于泉水的CO2分压远远高于空气, 泉水中的CO2大量逸出, 结果导致碳酸钙过饱和而发生沉积; (2)黄龙钙华的颜色以黄色为主色调, 主要是在雨季因雨水冲刷土壤向水中混入泥沙的缘故; 而在旱季, 钙华主要形成于清亮干净的泉水, 因此, 钙华的颜色呈现出纯净碳酸钙沉积的本色-白色。这也是黄龙洞钙华剖面年层中出现黄-白相间亚层的原因; (3)高精度的铀-钍同位素测年表明, 黄龙钙华主体是全新世以来形成的; (4)地表水向地下河的漏失是黄龙地表水日益减少, 导致钙华体表面干涸, 从而气生蓝藻大量滋生, 致使某些钙华变黑的主要原因, 因此, 有必要尽早采取防渗补水措施; (5)旅游活动已对黄龙钙华景观产生影响, 包括上游人为践踏使下游钙华池淤塞, 以及磷酸盐污染使硅藻等过度繁殖和钙华沉积速率可能降低等, 因此, 必须尽早采取相应防控措施。     

四川黄龙钙华藻类及其生物岩溶作用

从探索黄龙钙华的生物成因角度出发,对黄龙钙华藻类进行了采集、鉴定和分析,并对钙华藻类的生物岩溶作用做了初步探讨。研究得出黄龙钙华藻类分属于4门19属86种,优势种属为Tolypothrix属、Gloeocapsa属和Cymbella属。黄龙景区不同环境区域的优势藻类有所不同,藻类参与的碳酸盐沉积在不同岩溶景观中所起作用也有所差异。其中蓝藻参与的碳酸盐沉积主要表现于黄龙钙华坝景观的形成过程中,由硅藻参与碳酸盐沉积主要表现于斜坡滩华景观的形成过程中。藻类既能在钙华形成过程中发挥作用,藻类的生长也能侵蚀破坏钙华景观,在长期缺乏岩溶水补给的条件下,藻类对钙华景观的破坏性尤为突出。      

黄龙钙华景观形成及演化趋势研究

黄龙景区因拥有钙华源泉、彩池、滩流、瀑布等景观而享誉世界,其钙华景观的稳定性也为世人所关注。文章通过对与钙华景观形成密切相关的地质环境,特别是水循环系统动态变化及区域钙华景观成长演化历史的研究,认为黄龙钙华景观现状稳定性较好,但正处于缓慢的、反复的衰退过程,只要采取适当的措施可以延缓其衰退。     

四川黑水卡龙沟钙华形成影响因素

四川黑水卡龙沟的地貌是典型的高寒岩溶作用下形成的钙华堆积地貌,其钙华堆积量巨大且钙华景观类型丰富,享有"中国苔藓泉华世界"之美誉。与黄龙的钙华景观相比,卡龙沟的钙华景观表面多覆盖有大量的藻类、苔藓等植物,形成了丰富的生物钙华景观。钙华的形成通常是岩石、水、大气、生物等多方面相互作用的结果。通过对卡龙沟钙华体形成造成影响的因素进行列举并适度分析,望有关认识能对今后卡龙沟钙华的进一步研究提供依据。     

四川黑水卡龙沟钙华形成影响因素

四川黑水卡龙沟的地貌是典型的高寒岩溶作用下形成的钙华堆积地貌,其钙华堆积量巨大且钙华景观类型丰富,享有"中国苔藓泉华世界"之美誉。与黄龙的钙华景观相比,卡龙沟的钙华景观表面多覆盖有大量的藻类、苔藓等植物,形成了丰富的生物钙华景观。钙华的形成通常是岩石、水、大气、生物等多方面相互作用的结果。通过对卡龙沟钙华体形成造成影响的因素进行列举并适度分析,望有关认识能对今后卡龙沟钙华的进一步研究提供依据。     

钙华体次生有机体系的界面结晶作用研究

本文总结了钙华体次生有机体系中生物群落特征和界面结晶行为,根据生物在碳酸盐沉积中的角色,将钙华体中次生有机体系的界面结晶矿化类型分为生物控制矿化沉积和生物诱导矿化沉积。分述了碳酸钙沉积矿化相关的五种生物代谢活动,讨论了生物胞外聚合物（EPS）对碳酸钙矿物晶型和形貌的影响。针对目前钙华研究中存在的问题,今后应深入研究生物体主要构成元素、生物小分子和生物体内部组织在钙华形成或退化中的作用,进一步厘清钙华体与次生有机体系的多界面溶化方式,为钙华保护修复及钙华退化治理措施提供科学依据。      

松潘黄龙水循环及钙华景观成因研究

通过对松潘黄龙风景名胜区主景区黄龙寺沟运用水均衡原理和水化学系统分析，并结合天然同位表示综技术，初步查明了黄龙水循环规律，确立黄龙钙华的源泉为转花泉，其源泉来源于大气降水，并经深循环补给。进而阐明了钙华的形成与演化，建立了黄龙水循环模式，用于保护和合理开发松潘黄龙自然景观资料，使之可持续利用。     

Petrography and textural development of inorganic and biogenic lithotypes in a relict barite tufa deposit at Flybye Springs, NT, Canada

A relict mound of Holocene barite (BaSO₄) tufa underlies the Flybye Springs, a small, barium‐rich, cold sulphur spring system in the Northwest Territories of Canada. The tufa is composed of relatively pure barite with ≤0·34 wt% Ca²⁺ and ≤0·77 wt% Sr²⁺. The mound is made up of coated bubble, raft, undulatory sheet, stromatolitic, coated grain and detrital conglomerate barite tufa. Although previously unreported in barite, these lithotypes are akin to facies found in many carbonate spring deposits. Raft and ooid‐coated grain tufa was formed via ‘inorganic’ barite precipitation in spring water ponds and tributaries where rapid oxidation of sulphide to sulphate established barite supersaturation. Undulatory sheet tufa may have formed by the reaction of dissolved barium with sulphate derived from the oxidation of extracellular polysaccharide‐rich colloidal sulphur films floating in oxygenated, barite‐saturated spring water ponds. Coated bubble, oncoid‐coated grain and stromatolitic tufa with filamentous microfossils was formed in close association with sulphur‐tolerant microbes inhabiting dysoxic and oxygenated spring water tributaries and ponds. Adsorption of dissolved barium to microbial extracellular polysaccharide probably facilitated the development of these ‘biogenic’ lithotypes. Detrital conglomerate tufa was formed by barite cementation of microdetrital tufa, allochthonous lithoclasts and organic detritus, including caribou hair. Biogenic textures, organic artefacts and microfossils in the Flybye barite tufa have survived diagenetic aggradational recrystallization and precipitation of secondary cements, indicating the potential for palaeoecological information to be preserved in barite in the geological record. Similarities between the Flybye barite tufa and carbonate spring deposits demonstrate that analogous textures can develop in chemical sedimentary systems with distinct mineralogy, biology and physiochemistry.     

Assessment of the collapse mechanisms of tufa deposits

This research assesses the collapse mechanisms of tufa deposits. The city of Antalya, located on the Mediterranean coast of Turkey, has been settled on tufa deposits. By the end of 1980s, the area behind the tufa cliffs became the site of high-rise residential buildings. Some of these buildings have suffered from foundation instabilities, which have given rise to cracking and fissuring of the walls, and overall tilting. The collapsible behaviour upon loading and/or wetting of some tufa deposits has caused foundation settlement.

Voids, bonding of grains and grain properties of the collapsible tufa were investigated using optical and scanning electron microscopes. Our studies indicate that the collapse behaviour of tufa is affected mainly by depositional environment and microfabric. Laboratory tests have been performed in order to determine the index properties and the collapse potential of tufa samples. Young tufa deposits near the surface are weakly bonded with thin films of carbonate cement, giving rise to high void ratios. Analysis of geotechnical parameters has shown that the collapse potential of tufa is closely related to the natural void ratio and the amount of cement binding the grains.     

四川九寨沟景区钙华起源初探

九寨沟风景区以绝美的景色闻名于世。钙华作为其独特景观的重要构成要素,有着重要的观赏价值和研究价值。为了弄清九寨沟钙华的起源,特别是CO2的来源,对九寨沟主要水体的水化学和碳氢氧同位素以及现代钙华的碳同位素进行了取样分析。结果发现:(1)九寨沟水体来源于大气降水的补给;(2)水体中碳酸氢根离子和钙离子浓度较低,主要来源于土壤CO2对碳酸盐岩的溶解;(3)根据碳的来源分类,九寨沟钙华应为大气成因类钙华(或表生钙华);(4)九寨沟珍珠滩钙华与碳酸氢根间较大的碳同位素分馏表明,此处生长的藻类对钙华的形成可能有重要作用。      

Analysis of Karst Tufa from Guangxi, China

The paper presents an analysis of characteristic karst tufa from Guangxi, China, which has not been studied before. A comparison with tufa from Dinaric Karst of Croatia is discussed in view of the C-type climate. The major mineral is calcite. Minor minerals are quartz and dolomite, depending on location. The content of calcium carbonate varies from 65% to 92%, and that of magnesium carbonate from 0.03% to 1.77%. Among other elements, the most abundant are Fe, from 0.02% to 1.50%, and Ti, from 0.15% to 0.27%. Many other trace elements (V, Cr, Mn, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Hg and Pb) are also present. Specific activity of radionuclides 40K, 232Th, 137Cs, 226Ra and 238U varies from sample to sample. Concentration of U in tufa is close to that reported for sedimentary carbonate. Low concentration of 137Cs indicates that this part of the world was not exposed to nuclear explosions. The concentration of 226Ra is the highest in Mashan County. The ratio 238U/226Ra (0.21-0.71) in tufa from Mashan Co     

柯坪硫磺沟奥陶系（纹层状）古钙华的特征及石油地质意义

天山南缘从柯坪阿恰经巴楚三叉口到巴楚五道班的100余公里的316国道北侧的奥陶系中发育了一条1~2 km宽的碳酸盐岩岩溶带。在该带的鹰山组中发育了一条900 m宽的风化壳沉积（古土壤）和约30多个大型古溶洞。其中以硫磺沟2号溶洞最为典型,该溶洞位于一个很窄的倾角大于70°的走滑断裂带内,古钙华一般产在溶洞和裂缝中,作为充填体出现。硫磺沟2号溶洞的古钙华多呈黄褐色-黑色,普遍含石油。古钙华纹层发育,根据结构、颜色及形态等可以分为六种,分别为层状纹层、波状纹层、包壳状纹层、束状纹层、丘状纹层或半球形丘状纹层和杂乱纹层,这些纹层的形态和结构特点反映了其成因与菌藻或微生物有关;构成纹层的方解石主要为针状、柱状、细晶状和粗晶状等。钙华方解石晶体之间缝隙和孔隙非常发育,是良好的储集空间和运移通道。物性研究表明,硫磺沟2号溶洞古钙华的孔隙度介于3.81%~13.91%之间,平均7.21%,从孔隙度值来看属于致密储层（10%）;但渗透率很大,介于（2.99~87.60）×10-3μm2之间,平均48.99×10-3μm2,从渗透率看是一种较好的储层。出现这种“反常”的情况与古钙华特殊的内部结构有密切关系,钙华以晶间缝为主,具有紧密堆积的结构,虽然孔隙度不大,但是晶间缝在三维上构成了网络系统,导致渗透性很好,被称之为“致密高渗”储层。通过对塔里木盆地北部柯坪奥陶系露头硫磺沟2号溶洞及现代九寨沟溶洞的研究,发现岩溶过程中的化学沉积形成的钙华具有重要的石油地质意义,主要表现在两个方面:一是钙华是很好的储集空间;二是钙华具有一定的生烃能力。文章旨在探讨塔里木盆地奥陶系露头钙华相、钙华岩石学及钙华地球化学证据,以支持钙华的形成过程和形成环境的解释、及对塔河油田奥陶系缝洞油气藏的储集空间和油气成藏意义。      

Three-dimensional modelling of a Holocene tufa system in the Lathkill Valley, north Derbyshire, using ground-penetrating radar

Unlithified and partly lithified carbonate sequences are ideally suited to the application of ground‐penetrating radar (GPR), augmented by percussion augering and shallow seismic techniques, all tied to present‐day topography using global positioning system (GPS) methods. This methodology provides the first clear information on the distribution and geometry of lithofacies within buried tufa complexes. The approach has been applied to a thick succession of Holocene tufas filling a gorge site along a 3·5‐km length of the River Lathkill, north Derbyshire. Earlier studies have demonstrated the presence of up to 16 m of tufas and sapropels associated with two transverse tufa dams (barrages). These strata have been accumulating throughout the Holocene, although tufa developments at present are of minor extent. Internal tufa morphologies are recorded by GPR as ‘bright’, laterally continuous reflections for lithified, concretionary and lithoclast‐rich horizons. The ‘brightest’ reflectors occur within well‐cemented barrages and delineate core areas and prograding buttress zones. In contrast, unlithified lime muds and sapropels produce low‐contrast reflections. Lithostratigraphic control and depth calibration of the GPR profiles was provided by percussion augering at selected sites. Six distinct lithofacies and four secondary barrages are identified in the study. Constructional and destructional events can be identified and correlated within the GPR profile network, and the internal growth morphologies of the barrages are apparent. GPR profiles also clearly define the evolution of the facies geometries. Three phases of tufa development can be recognized within the GPR data and greatly extend our understanding of Holocene tufa‐forming processes in valley sites: (a) Early Holocene barrage build‐ups but with limited paludal deposition; (b) Middle Holocene ponding and sapropel accumulation under ‘warm’ conditions; and (c) Late Holocene barrage termination and valley levelling, probably coincidental with anthropogenic activity. This type of multidisciplinary approach should be considered as an essential prerequisite to all biostratigraphic and geochemical studies of Holocene freshwater carbonate sites.     

黄龙钙华210Pb计年与现代沉积的环境变化研究

本文以黄龙钙华岩芯为主要研究对象,利用210Pb定年技术在测定年轻碳酸盐样品短时间尺度上的优势建立了研究区近100年来高精度的年代标尺及环境记录;通过碳氧稳定同位素的分析,讨论了钙华稳定同位素记录与器测气候数据的相关性特征,并与其他定年技术所获得的结果进行了相互验证.研究区钙华δ18O在1908~2004年时段内的变化范围为-12.13‰~10.42‰,平均值为-11.23‰,变化幅度达到了1.7‰.同属西南季风区、由于海拔效应和距离水汽来源远近不同等因素的影响,在同时段内黄龙钙华δ18O.的变化范围和变化幅度都比董歌洞和Kahf Defore洞的δ18O记录要大,说明处于中纬度、高海拔的黄龙钙华相对于低海拔的董歌洞和Kahf Defore洞石笋对气候环境的响应可能更加敏感.     

Travertine formation in Plitvice National Park, Yugoslavia: chemical versus biological control

Hydrochemical studies of the Plitvice Lakes and their tributaries (Croatia/Yugoslavia) were coupled with micromorphological investigations on carbonate lake sediments and recent travertines. Karst springs discharge water from aquifers in Triassic and Jurassic dolomites and limestones and collect in lakes, which are ponded behind accreting travertine dams. Waters at springs have a high CO₂ partial-pressure (greater than 7000 ppm) and are slightly undersaturated with respect to calcite (saturation index less than —0·03). CO₂ partial pressure is quickly reduced in swift running streams, leading to very high supersaturation with carbonate minerals (saturation indices between 0·74 and 0·53). Calcite deposition, however, is restricted to the lake bottoms (formation of lake marl) and to the tufa dams. The annual carbonate precipitating capacity of the system based on water balance and downstream loss of dissolved ions is estimated to be on the order of 10 000 t CaCO₃ as cascade deposits (tufa dams) or as micrite in lakes behind the travertine dams. The initial stages of travertine formation as a result of morphological, biological, and chemical factors are (i) moss settling on small ridges in the creek courses, (ii) epiphytes (diatoms and cyanobacteria) settling on the moss surface, (iii) micrite particles resuspending from lake bottoms and being trapped on mucous excretions from bacteria and diatoms, and (iv) inorganic calcite precipitating as sparite at nucleation sites provided by these crystal seeds. Geochemical studies of the lake marl and tufa dams show that amino acids are dominated by aspartic acid. Carbohydrates come from structural polysaccharides of diatoms. The sticky excretions, rich in aspartic acid, are necessary for the initiation of calcite precipitation. They may be a response of algal and bacterial metabolism to environmental stress by either nutrient depletion or high calcium concentrations in ambient waters. The formation of tufa and micrite (lake marl) appears to be initiated by localized biological factors and is not governed by mere calcite supersaturation of the water. Oligotrophy may be an essential precondition for the formation of fresh water carbonate deposits.     

Stable and clumped isotopes in desert carbonate spring and lake deposits reveal palaeohydrology: A case study of the Lower Jurassic Navajo Sandstone,south‐western USA

Carbon, oxygen and clumped isotope (Δ₄₇) values were measured from lacustrine and tufa (spring)‐mound carbonate deposits in the Lower Jurassic Navajo Sandstone of southern Utah and northern Arizona in order to understand the palaeohydrology. These carbonate deposits are enriched in both ¹⁸O and ¹³C across the basin from east to west; neither isotope is strongly sensitive to the carbonate facies. However, ¹⁸O is enriched in lake carbonate deposits compared to the associated spring mounds. This is consistent with evaporation of the spring waters as they exited the mounds and were retained in interdune lakes. Clumped isotopes (Δ₄₇) exhibit minor systematic differences between lake and tufa‐mound temperatures, suggesting that the rate of carbonate formation under ambient conditions was moderate. These clumped isotope values imply palaeotemperature elevated beyond reasonable surface temperatures (54 to 86°C), which indicates limited bond reordering at estimated burial depths of ca 4 to 5 km, consistent with independent estimates of sediment thickness and burial depth gradients across the basin. Although clumped isotopes do not provide surface temperature information in this case, they still provide useful burial information and support interpretations of the evolution of groundwater locally. The findings of this study significantly extend the utility of combining stable isotope and clumped isotope methods into aeolian environments.