Interaction of rock and atmosphere: patinas on Mediterranean monuments

 This paper analyzes – chemically, mineralogically, and petrolographically – the patinas developed on several Mediterranean monuments made with different stones (siliceous and carbonatic) in order to establish their origin and their evolution under the present environmental conditions, and to evaluate the environmental parameters controling their development. Most of the patinas show a common sequence of layers, which, from the outer to the inner zone, are: (1) present bioactivity and/or biological remains, (2) gypsum-rich patina, and (3) calcitic brown to orange patina. Each one may exhibit different fabrics (from micritic to stromatolitic) and may be more or less continuous and homogeneous. The main mineral components are calcite and gypsum, but Ca-oxalates and Ca-phosphates have also been found associated to biological structures, as well as quartz and clays. The different fabrics and textures have been interpreted as consequence of changes in the environmental conditions which seem to be related to the biological activity, facilitating the growth of different organisms and leading to the development of a deposit with distinct characteristics (fabric, texture, porosity, etc.). The gypsum-rich patina has been interpreted as a sulphation of the underlying calcitic layer by the action of atmospheric pollutants or as dry or wet deposition from the atmospheric dust. The mineralogy and texture of the patina is independent of the nature of the underlying rock and only in few cases a micritization process has been observed as interaction between patina and rock. Recently, the penetration of endolithic microflora produced drillings and the development of a fissuration system parallel to the surface, and thus the detachment of the crust from the rock and even flackening of the rock itself has been observed. Consequently, under the present climatic conditions in the Mediterranean basin, erosion is a more active process than deposition, and the crusts and patinas show a tendency to disappear from the surface of the monuments. Received: 3 November 1996 · Accepted: 10 September 1997     

Assessing the contribution of electrical resistivity tomography (ERT) and self-potential (SP) methods for a water well drilling program in fractured/karstified limestones

ERT and SP investigations were conducted in carbonate rocks of the Dinant Synclinorium (Walloon Region of Belgium) to find suitable locations for new water wells in zones with little hydrogeological data. Since boreholes information needed to be representative of the area, large fractured zones were searched for the drillings. Large ERT profiles (320 to 640 m) allowed us to image the resistivity distribution of the first 60 m of the subsurface and to detect and characterize (in terms of direction, width and depth) fractured zones expected to be less resistive. Data errors, depth of investigation (DOI) indexes and sensitivity models were analyzed in order to avoid a misinterpretation of the resulting images. Self-potential measurements were performed along electrical profiles to complement our electrical results. Some negative anomalies possibly related to preferential flow pathways were detected. A drilling campaign was conducted according to geophysical results. ‘Ground truth’ geological data as well as pumping tests information gave us a way to assess the contribution of geophysics to a drilling program. We noticed that all the wells placed in low resistivity zones associated with SP anomalies provide very high yields and inversely, wells drilled in resistive zones or outside SP anomalies are limited in terms of capacity. An apparent coupling coefficient between SP signals and differences in hydraulic heads was also estimated in order to image the water table.     

云南省兰坪县来龙铅锌矿控矿因素

来龙铅锌矿属热液脉型铅锌矿床,矿体产于上三叠统三合洞组（T3s）灰岩层间破碎带中,矿体受断裂破碎带控制明显.围岩蚀变有硅化、白云石化、方解石化、炭化、褐铁矿化等.其中白云石化、方解石化、褐铁矿化与成矿较密切.     

A new section of Lower Palaeozoic rocks in Kayin State (Southeast Myanmar)

Lower Palaeozoic rocks have been mapped in Kayin State in an area previously shown on published maps as either metamorphic or possibly Lower or Upper Palaeozoic rocks. Three new formations, with a total thickness of over 900?m, apparently overlain by an, at least, 100?m thick Upper Palaeozoic formation are mapped along the Salween River and along the road from Yinbaing, in Myanmar, to Tha Song Yang, in Thailand. The Lower Palaeozoic succession consists of the predominantly siliciclastic Kyaukpulu and Kushwe–e–we formations and an overlying, predominantly carbonate Meseik Ashe Formation which contains Middle Ordovician (Darriwilian) conodonts. The older two formations are probable correlates of the Ngwetaung and Lokeypin formations of the southern Shan State of Myanmar and the Lower Ordovician siliciclastics of western Thailand. The overlying, peritidal to shallow subtidal carbonates of the Meseik–Ashe Formation are correlates of the Wunbye and Sitha formations of Shan State, Myanmar. The thick–bedded, quartz arenites of the Nyaungwiang Formation are faulted against the Ordovician carbonates and are probable lithological correlates of the Carboniferous Taungnyo Formation. The folds in the Lower Palaeozoic rocks are overturned to the northeast and deformation was in one major phase between the Tournaisian and the Early Permian. The Lower Palaeozoic strata may probably be followed as a ridge for at least 100?km towards the NNW, close to the western border of the Sibuma Block which is separated by a postulated cryptic suture from the Irrawaddy Block to the west.     

Early Permian ammonoids from the Kaeng Krachan Group of the Phatthalung-Hat Yai area, southern peninsular Thailand

An Early Permian small ammonoid fauna consisting of Neocrimites sp., Agathiceras suessi Gemmellaro, A. girtyi Böse, Agathiceras? sp., and Miklukhoceras sp. was found in nodules of a fine sandstone bed exposed in the Phatthalung-Hat Yai area of southern peninsular Thailand. The ammonoid-bearing bed belongs stratigraphically to the uppermost part of the Kaeng Krachan Group, which is essentially a clastic-dominant, Late Carboniferous (?) to Early Permian stratigraphic unit, widely distributed in western and peninsular Thailand. This ammonoid fauna is considered to be of Bolorian (Kungurian) age and includes Agathiceras girtyi Böse, which is described for the first time from Thailand. The present discovery of Bolorian ammonoids suggests that the uppermost part of the Kaeng Krachan Group is slightly younger than previously considered and around the latest Early Permian. This further implies that the continental margin environment of the Sibumasu Block drastically changed at around Bolorian time from a cool, clastic-dominant shelf condition to a temperate to subtropical, carbonate platform due to rapid northward drift after middle Artinskian rifting.     

老挝琅勃拉邦爬奔金矿矿床地质及成因探讨

琅勃拉邦省位于“三江”成矿带南延部分,爬奔金矿为受剪切带控制的低温热液矿床,矿体产出空间符合里德尔剪切裂隙规律,进一步工作后该矿区应有中型以上规模。     

Florida Bay: Modern analogue for Lofer cyclothems?

Lofer cyclothems of the Alpine Upper Triassic have many features in common with Holocene sediments of Florida Bay. The modal ‘complete’ Lofer cycle is essentially symmetrical, having a deepening and shoaling phase, as does the cycle-in-progress in Florida Bay. Lateral discontinuity and thickness variations within members of the Lofer cyclothems indicate syn-depositional relief, possibly in the form of mud banks, the signature feature of Florida Bay sedimentation. Spatial and temporal dimensions, although poorly constrained, appear comparable. Analogous depositional textures, biota and sedimentary structures, while not unique to either environment, strengthen the inferences that can be made about the Triassic depositional environment and regarding future evolution of the modern environment. The striking similarities between the Holocene icehouse sediments and the Late Triassic greenhouse deposits suggest that sedimentation patterns at the scale of individual cycles or parasequences may be largely independent of the global climate regime.     

The application of rock mass classification systems to underground excavation in weak limestone, Atatürk dam, Turkey

The Atatürk dam was built across the Firat River on clayey limestone. A grout curtain, providing impermeability in the left and right abutments, was done in grouting galleries. The well known rock mass classification systems for tunneling purposes [rock structure rating (RSR), rock mass rating (RMR) and rock mass quality index (Q)] were used to classify the rock mass along these galleries. Based on RSR, RMR and Q values, the rock masses in the galleries have been classified into three different classes. Correlation between the three classification systems is discussed and suggestions are made for using rockbolt, shotcrete with wiremesh and steel ribs for supporting the rock mass.     

岩溶生态系统中的土壤

在偏碱富钙的岩溶生态系统中,其土壤具以下特征：①形成速率十分缓慢,形成1 m厚的土层需要250～7 880 ka,因而对岩溶区土壤侵蚀的评价应有新的认识;②高含量的钙离子使土壤腐殖质中胡敏酸的含量比例较高,且稳定性好,不易分解的腐殖质使石灰土供应营养元素具缓效性;③微量营养元素含量及有效态具有不平衡性,且随钙镁含量的降低,其有效率显著提高;④粘粒含量高,当有机质含量高时,具有良好的团粒结构,有较好的供水、供肥能力,反之其团粒结构就失去稳定性,使土壤有效水含量、抵御水土流失的能力降低;⑤岩溶地貌制约石灰土的类型及分布,并延缓其向地带性土壤演化。因此石灰土资源的有效利用应从岩溶学、土壤学与植物学相互协调的角度进行生态经济规划。