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。     

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。      

基于微岩相分析的藻类在钙华沉积中的作用研究——以四川黄龙为例

在地表环境下,钙华沉积常常是物理化学和生物沉积过程共同作用的结果。藻类因其在钙华沉积环境中具有较大的生物量及其自身拥有多样的代谢方式,对钙华沉积过程和形态具有重要影响。本研究以四川黄龙钙华为例,通过对典型沉积点的水化学、藻类群落组成和现代钙华微岩相结构进行综合分析,来揭示藻类在钙华沉积中的作用。研究发现,黄龙钙华沉积环境中分布的藻类主要包括蓝藻、绿藻和硅藻等。这些藻类代谢活动会在一定程度上改变沉积水体水化学环境,但在快速流动的水体中,其影响有限。不同藻类群落常常形成几百微米至1~2 mm厚的微生物席或生物膜层,作为碳酸钙沉积发生的重要场所,即钙华沉积活动层。在该活动层内,藻体及其分泌的胞外聚合物（EPS）能够为碳酸钙晶体生长提供大量成核位点和生长模板,从而极大地促进钙华沉积。同时,EPS可以控制或影响碳酸钙结晶形态及钙华微岩相结构。准确认识和量化藻类在钙华沉积中的作用还需要继续开展更多微观尺度方面的研究,以便更好地理解钙华沉积机制,并为准确解译古老钙华岩相结构和地球化学特征奠定基础,同时为预测钙华景观演化和保育提供更多科学依据。      

黄龙景区水循环系统与景观演化研究

黄龙景观的形成演化受景区水循环系统控制。本文研究表明,黄龙景区水系统由后沟地表水系统、钙华源泉地下水系统和核心景区水循环转化系统三部分组成。其中,后沟地表水系统对景观形成与演化主要是水量的贡献,钙华源泉则提供了钙华沉积的物质来源,两者混合后构成景观补给水源并在核心景区经多次转化形成二次转化系统。二次转化系统又分为四个转化段及相应的四个钙华沉积和景观演化段。     

黄龙与黄石钙华微生物沉积作用比较研究

本文通过调查黄龙风景区水体的环境地质特征与微生物群落结构及多样性,并与黄石公园对比分析,探讨了两种特殊地理环境下的微生物群落结构和多样性及其对钙华沉积的影响。结果表明:黄龙沟泉水属于地下冷泉,且景区内覆盖着大量植被,水体中有大量藻类和细菌;黄石公园猛犸象温泉区泉水属于地下热泉,植被覆盖率很低,泉水中微生物多为嗜热菌,藻类较少。黄龙与黄石钙华主要由方解石组成并且微生物参与了钙华的形成过程。微生物对钙华沉积的作用,主要分为模板作用、产物诱导作用和代谢调控作用,对比探讨了特殊地质环境下的微生物对钙华沉积的贡献,指出微生物沉积作用在钙华沉积过程中的重要性,可为黄龙钙华“黑化”防治提供理论依据。      

黄龙钙华体的碳酸盐溶质输入输出量及演化阶段

黄龙钙华体为次生碳酸盐岩,通过对外来水的碳酸盐溶质向钙华体的输入量和钙华体循环水的碳酸盐溶质向涪江输出量的计算,它处于入不敷出的现状,结合钙华体综合地貌分区,其沉淀分区面积远小于剥蚀溶蚀分区面积,采用上述定量法和定性法研究均得出黄龙钙华体步入衰退的老年期,这与四川西北部钙华体群所处的老年期发育阶段相同,是受区域地质环境的作用和影响所至,这一演化趋势是不可逆转的,但可以运用现代岩溶理论结合其他学科知识以科技工程方法阻缓衰退的步履。     

松潘黄龙钙华演化趋势研究

黄龙主沟露天钙华分布面积为634 712m2,最大厚度为19.72m.在3.5万年以来的演化过程中形成了绚丽多姿的钙华彩池、钙华滩流、钙华瀑布、钙华洞穴等景观.它被誉为"人间瑶池",是世界著名的旅游胜地.其中钙华彩池105 932m2,钙华滩流157 882m2.根据钙华在演变过程中所处的阶段可划分为成长区、平衡区、消退区、非沉积区等4个演化分区.钙华景观的发展演化不由其形成时代的新老决定,而与自身所处的地质背景、水循环系统控制下的钙华源泉的稳定性密切相关.目前,黄龙钙华景观主体处于青壮年期.     

四川康定县玉农希钙华景观及其水循环系统

地处康定县贡嘎山西侧的玉农希钙华景观是继九寨沟、黄龙钙华景观发现之后又一具有世界遗产潜质的高寒岩溶风景地。本次调查工作是四川省国土资源厅安排的四川省重点地质遗迹保护可行性规划的第二批项目。项目首次对玉农希钙华景观进行了较系统的调查研究, 从地质遗迹景观及形成景观的水循环的角度查明了钙华景观的特征, 剖析其景观形成的水循环系统, 进而作了区域性对比分析, 初步探索其形成机理与演化规律。玉农希钙华具有极高的科学价值、美学价值和观赏价值, 可与九寨、黄龙媲美, 必须采取科学、合理的措施对其加以保护。     

黄龙钙华景观演化特征及保护措施探讨

黄龙景区因其拥有千姿百态、色彩斑斓的钙华景观而享誉世界,本文从钙华景观的演化特征及演化周期研究出发,认为景观区内钙华的退化仅仅是局部的和反复的,而景观的演化具有明显的周期性,其演化的周期约为300 a.同时,通过分析得出水循环系统、水流改道及流态和景观水的漏失等是影响黄龙钙华景观演化的主要因素,并提出了有针对性的保护措施建议.     

A preliminary analysis of the formation of travertine and travertine cones in the Jifei hot spring,Yunnan, China

The Jifei hot spring emerges in the form of a spring group in the Tibet–Yunnan geothermal zone, southwest of Yunnan Province, China. The temperatures of spring waters range from 35 to 81°C and are mainly of HCO₃–Na·Ca type. The total discharge of the hot spring is about 10 L/s. The spring is characterized by its huge travertine terrace with an area of about 4,000 m² and as many as 18 travertine cones of different sizes. The tallest travertine cone is as high as 7.1 m. The travertine formation and evolution can be divided into three periods: travertine terrace deposition period, travertine cone formation period and death period. The hydrochemical characteristics of the Jifei hot spring was analyzed and compared with a local non-travertine hot spring and six other famous travertine springs. The results indicate that the necessary hydrochemical conditions of travertine and travertine cones deposition in the Jifei area are (1) high concentration of HCO₃ ⁻ and CO₂; (2) about 52.9% deep source CO₂ with significantly high value; (3) very high milliequivalent percentage of HCO₃ ⁻ (97.4%) with not very high milliequivalent percentage of Ca²⁺ (24.4%); and (4) a large saturation index of calcite and aragonite of the hot water.     

Cool water geyser travertine: Crystal Geyser,Utah, USA

A sloping travertine mound, approximately 85 m across and a few metres thick is actively forming from cool temperature waters issuing out of Crystal Geyser, east‐central Utah, USA. Older travertine deposits exist at the site, the waters having used the Little Grand Wash Fault system as conduits. In contrast, the present Crystal Geyser travertine mound forms from 18°C waters which have been erupting for the last 80 years from an abandoned oil well. The present Crystal Geyser travertine accumulation forms from a ‘man‐made’ cool temperature geyser system; nevertheless, the constituents are an analogue for ancient geyser‐fed carbonate deposits. The travertine primary fabric is composed of couplets of highly porous, thin micritic laminae intercalated with thicker iron oxide rich laminae. Low Mg‐calcite is the dominant mineralogy; however, aragonite is a major constituent in deposits proximal to the vent and decreases in abundance distally. Cements exhibit a variety of fabrics, isopachous being common. Constituents include micro‐stromatolites, clasts, pisoids and the common occurrence of Frutexites‐like iron oxide precipitates. Leptothrix, a common iron‐oxidizing bacterium, is believed to be responsible for the production of the dense iron‐rich laminae. Pisoids litter the ground around the vent and rapidly decrease distally in abundance and size.     

Characterization of sulfate ion in travertine

The mode of incorporation of sulfate ion in travertine was discussed on the basis of chemical compositions, i.r. and laser Raman spectra. These data strongly suggest that most of the sulfate ions in the calcitic travertine replace carbonate ions. This conclusion is in good harmony with the facts that calcite incorporates more sulfate ions than aragonite does and that the sulfate content of manganoan calcite decreases with increasing manganese content (Takano et al. 1977). Based on this conclusion, retarding effect of sulfate ion on the precipitation of calcite from solution was discussed.     

Hot-spring travertine facies and sequences, Late Pleistocene, Rapolano Terme, Italy

Late Pleistocene travertines up to 40 m thick near Rapolano Terme in Tuscany, central Italy, were precipitated by hot water issuing from springs on hillsides and flowing into adjacent depressions to mix with rainwater. Proximal light-coloured slope and terrace travertines pass distally into darker reed mound and depression-fill travertines. Lithotypes include crystalline crust, shrub, pisoid, paper-thin raft, coated bubble, reed, and lithoclast-breccia. High precipitation rates resulted in rapid slope aggradation and progradation. Dilution by rainwater likely lowered precipitation rates in depressions, but deposition was augmented by allochthonous material eroded from upslope travertines. Slope Depositional Systems consist of Smooth and Terrace Slope facies characterized by white crystalline crusts, with diverse additional lithotypes in terrace pools. Depression Depositional Systems have mixed light and dark travertines with horizontal to gently concave stratification. Extensive light-coloured Shrub Flat travertine is dominant; darker Marsh-Pool Facies composed of fine lithoclast and reed travertine is localized. Reed Mounds composed of mixed light and dark travertines localized by abundant reed growth, formed where spring water emerged near the bases of low angle slopes. Distal reduction in accretion rate was the major influence on sequence development. Light-coloured slope travertines interdigitate with darker depression deposits. Vertical aggradation of slope deposits, mound progradation, and filling of topographic depressions is expressed by advance and retreat of facies. Evolution from depression to slope or mound sequences is termed ‘steepening up’. Up-sequence change from slope or mound to depression facies is termed ‘levelling up’. Exposure surfaces associated with palaeosols are common in all facies and often constitute sequence boundaries. They are more closely spaced in depression sequences, reflecting slower and possibly also more discontinuous accumulation at sites furthest from hot springs.     

山西介休洪山钙华的空间分布特征、成因及时代探讨

地处山西省介休市洪山镇狐岐山脚下的钙华,是山西省内娘子关钙华景观之外的又一具有观赏潜质的岩溶景观。其出露范围较大,厚度稳定,形态优美,具有较高的旅游地质观赏价值。文章对洪山钙华进行了系统的地质调查和剖面实测,对钙华的分布范围、产出状态、岩石特征、岩石化学特征、地球化学特征及同位素年代等进行了研究,并从洪山泉岩溶水系统循环的角度,探讨了钙华的形成机理、影响因素及形成时代,可为该区钙化的保护和景观开发提供科学依据。      

Aragonite laminae in hot water travertine crusts, Rapolano Terme, Italy

Small (5–30 μm) aggregates of aragonite needles occur in calcite crystal crusts of present day hot water slope travertines at Rapolano Terme in Tuscany, Italy. The aggregates are mainly concentrated in irregular, wispy and dark laminae which cross-cut calcite crystal feathers to create a pervasive millimetre scale banded appearance in the deposit; they also occur less commonly scattered irregularly through the calcite layers. The aragonite needle aggregates are in the form of crosses, fascicles (sheaf shaped bundles, or dumbbell shaped), rosettes and spherulites. Locally, irregular masses of needles also occur. The fascicles, rosettes and spherulites have hollow centres which resemble microbial components (?fungal spores, bacterial colonies and pollen), suggesting that the aragonite crystals are biotically nucleated. The lamination is interpreted to reflect diurnal control. Stimulation of microbial activity during daylight concentrates cells in laminae and promotes aragonite calcification. Calcite feather crystals, although traversed by the aragonite aggregate laminae, have a clear appearance under the light microscope. They form more or less continuously through the diurnal cycle by abiotic precipitation. The constant association of aragonite with organic nuclei, irrespective of whether the latter are in laminae or scattered through the calcite layers, supports a biotic control on aragonite formation. Lamination in Pleistocene travertines is superficially similar to that in the present day deposits, but is diagenetically altered. In the Pleistocene deposits, the calcite feathers appear dark under the light microscope and the aragonite aggregates, where they are not altered to dark calcite, are dissolved, together with parts of the adjacent spar calcite, and therefore appear light coloured.     

Long-term analog of carbonation in travertine from Uleimat Quarries, Central Jordan

Quaternary travertine capping the metamorphic (cement) zones in Uleimat Quarries, central Jordan, has been precipitated from hyperalkaline paleogroundwaters. Such waters are similar to the cement pore water and to the present day hyperalkaline seepages (pH 12.5) in Maqarin, north Jordan. The isotopic depletions observed in Uleimat travertine, with δ¹³C values as low as −25.45‰, suggest that they have been precipitated during CO₂ uptake by highly alkaline calcium hydroxide waters. The travertine in Uleimat Quarries indicates a long-term analog of carbonation and remobilization of silica in cementitious barriers for radioactive waste repositories. The presence of Cr-rich smectites and relatively high levels of Cr (4.1%), V (657 ppm), Ni (163 ppm), Zn (634 ppm) and U (34 ppm) in the green travertine and the associated opaline silica phases suggests the use of the Uleimat travertines as analogs with the repository disturbed zone. Smectites and silica phases are expected to be a sink for alteration products in the late stage evolution of a high pH plume. Co-precipitation of these elements in mineral phases is of great importance to control the concentration of these elements in groundwater.     

Origin and diagenesis of Quaternary travertine shrub fabrics, Rapolano Terme, central Italy

Millimetre to centimetre sized arborescent shrub-like calcite precipitates are common constituents of hot water travertine shallow pool deposits of Quaternary age at Rapolano Terme, Tuscany, Italy. In the presently forming travertines, the shrubs consist of apparently random associations of (i) micrite aggregates and (ii) subhedral to euhedral rhombic spar crystal aggregates. In thin section, the micrite aggregates appear dark and the spar-rhomb aggregates light, giving the shrubs a mottled appearance. Travertines are basically produced by CaCO₃ precipitation due to degassing and evaporation of the spring waters, although biological influence may also stimulate precipitation. The formation of masses of erect shrubs, rather than dense crystal crusts that form on slopes, is probably due to limited water flow in the pool environments. Microbes, including bacteria and diatoms, are important influences on shrub microfabric and external shape. The micrite aggregates are associated with bacteriform bodies, seen as tiny rods and spheres. The micrite precipitates around these bodies and in adjacent biofilm. Spar-rhomb precipitation appears to be external to the biofilm, and may be related to the presence of diatoms which are locally closely associated with the spar-rhombs, although an essentially inorganic origin, particularly for the more euhedral rhombs, cannot be ruled out. In the older Quaternary travertines, the original microfabric of the shrubs has been diagenetically altered. The original mottled appearance of the shrubs has become uniformly dark and micritic, and the evidence for the dual micritic and spar-rhomb origin of the shrubs is obscured or destroyed. Spar-micritization of the shrubs is probably due to abiotic, and locally biotic, dissolution. Previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity.     

九寨沟诺日朗瀑布钙华震损机制分析

2017年8月8日九寨沟发生7.0级地震,景区内部分景观破损,其中诺日朗瀑布钙华体局部出现小规模坍塌。通过调查研究,查明了瀑布景观钙华的震损现状,结合二维离散元分析软件Universal Distinct Element Code (UDEC)对变形破坏过程进行了模拟分析,揭示了钙华震损过程分为振动蠕变、持续拉张、倾倒折断和溃屈破坏4个阶段。综合地质环境背景分析,景观钙华形成的地质环境条件和景区水流系统处于基本稳定状态,景观体处于相对稳定的发展阶段,层湖叠瀑景观不会消亡。     

黄龙钙华纹层石特征与成因分析

为了探究黄龙钙华纹层石剖面褐-白相间混积纹层的特征与成因,对黄龙钙华样品进行了采集和分析。通过微波消解法分析不同颜色纹层钙华样品有机碳含量,并用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、元素分析仪等对样品的晶相、形貌、元素和Mg/Ca比等进行了分析。结果表明,黄龙钙华褐-白纹层有机碳含量、Mg/Ca比存在明显差异,褐色纹层有机碳含量、Mg/Ca分别高于相邻的白色纹层,有机碳的含量随着沉积顺序(由老到新)逐渐变大。钙华剖面年层中的褐-白相间纹层不仅受到微生物、植物等生物的影响,还受不同温度、水动力等气候因素的调控,即黄龙钙华剖面年层中出现褐-白相间纹层为生物-气候双成因。其结果可为寻找黄龙钙华沉积过程中生物参与证据提供一定的理论基础。