Geological Field Investigations Research Articles

Paragenesis and fluid evolution of the Halasu III porphyry Cu deposit, East Junggar (NW China): Implications for the Paleozoic multiphase superimposing mineralization in the Central Asian Orogenic Belt

The Halasu III deposit, an important Cu deposit in the southernmost part of the Halasu porphyry Cu belt, is situated in the East Junggar block in NW China. Copper and Mo sulfide mineralization commonly occurs as disseminations or veinlets, and is mainly associated with Devonian granodiorite porphyry. Our detailed field geological investigation identified late-stage high grade Cu sulfide-bearing veining superimposed on the earlier porphyry Cu–Mo mineralization.Four hydrothermal alteration and mineralization stages were identified, namely the early epidote alteration (Stage I), porphyry-style alterations (Stage II comprising II-A potassic, II-B propylitic and II-C phyllic alteration sub-stages), late veining (Stage III) and supergene processes (Stage IV) in the northern- and southern mineralization zones at Halasu III. Multiphase granodiorite- and alkali granite dykes intruded the Beitashan Formation volcanic rocks, generating the early epidote alteration. Potassic alteration (Stage II-A) occurred in and around the NNW-treading granodiorite dykes, while the propylitic alteration (Stage II-B) occurred in the intrusions or volcanic wall rocks around the potassic zone. These early alteration assemblages were overprinted by the subsequent, structurally-controlled phyllic alteration (Stage II-C) confined within the granodiorite porphyry. Late veins (Stage III) include sulfide-bearing (Stage III-A) and sulfide-barren (Stage III-B) ones. Supergene process (Stage IV), represented by hematite and jarosite replacing primary sulfides, extends tens of meters down depth and is commonly fracture-controlled.Three fluid inclusion (FI) types were recognized, namely Type A (single-phase), B (liquid–vapor two-phase) and C (liquid–vapor–solid three-phase). For Type B FIs, those of potassic alteration homogenized at 183–347°C, with corresponding salinities of 6.2–17.8wt.% NaCl equiv. The propylitic and phyllic FIs homogenized at 172–425°C and 231–352°C, respectively, with the corresponding salinities of 0.9–14.0wt.% NaCl equiv. and 0.4–10.5wt.% NaCl equiv. The sulfide-bearing vein FIs homogenized at 243–410°C (Stage III-A-1), 260–362°C (Stage III-A-2) and 117–235°C (Stage III-A-3), along with the corresponding salinities of 1.9–9.2wt.% NaCl equiv., 1.1–6.7wt.% NaCl equiv. and 6.5–17.1wt.% NaCl equiv., respectively. The sulfide-barren vein FIs yielded homogenization temperatures of 260–380°C (Stage III-B-1) and 114–297°C (Stage III-B-2), with corresponding salinities of 1.7–9.8wt.% NaCl equiv. and 0.2–13.6wt.% NaCl equiv., respectively. We suggest that hydrothermal veins at Halasu III may have undergone complex and superimposing alteration due to the episodic reopening of the preexisting veins, with Stage III-A-3 veining overprinting the phyllic alteration and Stage III-A-2 veining. Stage III-B-2 veining superimposed on the potassic alteration, as well as on Stages III-A-1 and III-B-1 veining.Paragenetic sequence and fluid evolution at Halasu III indicate that these complex hydrothermal alteration stages were formed in accordance with the regional tectonic evolution. These various alteration and mineralization stages at Halasu III deposit reveal a prolonged history of magmatic and hydrothermal processes extending episodically from the Middle Devonian to Middle Permian, wherein early mineralization was overprinted by late hydrothermal events. Such superimposed mineralization may occur commonly in the Paleozoic Central Asia Orogenic Belt.

Partial reactivation of a huge deep-seated ancient rock slide: recognition, formation mechanism, and stability

Abstract. About 18 years ago, a large-scale discontinuous layer in properties and colour was found in the new Fengjie town at the shore of the Three Gorges Reservoir area in China. There are many resettled residents and buildings on the sloping area, the safety of which is potentially affected by this layer, so it has become the focus of attention. Before this study started there were two viewpoints regarding the origin of this layer. One was that is was from a huge ancient slide and the other was that is was from a fault graben. In order to find out how it was formed and to be able to carry out a stability analysis of the slope the authors have carried out a research program, including geological field investigations and mapping, a deep drilling hole, a geotechnical centrifuge model test, and a simulation analysis. The results of the research led to the conclusion that the layer is the sliding plane of a huge deep-seated ancient rock slide, which we called the Sanmashan landslide. An important argument for the conclusion is the recognition of a regional compressive tectonic stress field in this area, which cannot lead to the formation of a fault graben because it needs a tensional tectonic stress field. Moreover, numerous unique geological features, sliding marks, and other relics of the ancient slide have been discovered in the field. The formation process of the ancient slide could be repeated in a large geotechnical centrifuge model test. The test shows that a deformation and failure process of "creep–crack–cut" has occurred. The type of the ancient slide can be classified as a "successive rotational rock slide". Finally, the role of seepage in the stability of the Sanmashan landslide has been analysed. Our final conclusions are that, during rainfall and filling–drawdown cycles in the Three Gorges Reservoir, the Sanmashan landslide as a whole is dormant and stable and the secondary landslides in the toe area of the slope are presently stable but can be reactivated. This research provides an important basis for the remedial measures and land use planning in the new Fengjie town, and a well-documented case history for researchers worldwide.

Late Pleistocene salt-water lake in the Linzhi area, southeastern Tibetan Plateau

A series of lacustrine terraces distributed upstream of Zhibai village in the Yarlung Tsangpo Gorge have been identified during the past tens of years. The precise age and formation of the paleolake provide evidence of the geological and geographical environment of the Yarlung Tsangpo Gorge in the past, especially the evolution of the river systems. A lacustrine terrace in Luxia village in the Linzhi area was the object of this study, because its well-preserved sediments provide ideal samples for sedimentological research. Continuous sediment samples were collected from two sections of the terrace, one in the middle part and the other at the bottom. This research combines field geological investigation, radiocarbon dating and analysis of chemical and mineral compositions to study the sedimentary features of the lacustrine terrace and to reconstruct the salinity and classification of the paleolake. Fourteen samples were collected from the middle sampling profile and were dated by accelerator mass spectrometry radiocarbon dating. The measurements were conducted in the BETA Analytic radiocarbon dating laboratory in Miami and the measurements were calculated using Oxcal 4.2. The radiocarbon dating results yield an age range of 45–31 ka, during the Late Pleistocene. All the 27 samples from the two sampled sections were determined to consist mostly of clay minerals based on scanning electron microscopy observations. Analysis of the X-ray diffraction spectrum of the clay minerals demonstrated that illite is the predominant constituent, followed by chlorite, and the contents of smectite and kaolinite are very small. The low numbers of the chemical index and integral breadth of illite indicate that the illite in the samples is rich in Fe and Mg and has perfect crystallinity, leading to the conclusion that the clay minerals in the lacustrine sediments were formed mainly through physical weathering processes. Geochemical analysis of the samples shows that the concentration of boron is comparatively high, from less than 40 μ g/g at the bottom of the profile to 75 μ g/g at the top. The boron concentration of clay minerals can be correlated with the paleosalinity of the waterbody in which the clay minerals were deposited. Of the different methods to calculate paleosalinity based on the boron-salinity relationship, the validity of the Couch Formula has been established over the past several decades. The Couch Formula accounts for the different capacities of boron absorption of different kinds of clay minerals, and the method is applicable to a considerable salinity range, between 0‰ and 70‰. In this study, we calculated the paleosalinity of the lake using the Couch Formula, which yielded a paleosalinity of more than 1‰, ranging from 4.5‰ to 8.5‰. In addition, the paleosalinity showed an increasing trend from the bottom of the sampling profile to the top. Salinity plays an important role in understanding the chemical features of a water body, and a salinity of 1‰ is commonly used to distinguish fresh-water from salt-water lakes. The paleolake in the Linzhi area was a salt-water lake. We hereby conclude that a salt-water lake, which existed from at least 45 to 31 ka during the Late Pleistocene, was present upstream of the Yarlung Tsangpo Gorge. The salt-water paleolake was a landlocked body of water that lacked an external outflow. The clay minerals deposited in the paleolake were formed in a physical-weathering-dominated environment. The results of this study indicate that the drainage networks of the Southeastern Tibetan Plateau may have been substantially different from those of the present day.

Sedimentary characteristics of the Lower Cambrian Niutitang shale in the southeast margin of Sichuan Basin, China

The Lower Cambrian Niutitang formation shale in the Sichuan Basin is not only a source rock for the Sinian conventional gas reservoir but also a possible reservoir for shale gas. However, very limited work have been focused on the detailed sedimentary environment related to shale gas exploration. In this study, detailed field geological investigation, continuous sampling and analyses by SEM, EDS XRD, XRF and ICP-OES, were used to probe provenance and sedimentary environment of the Niutitang formation shale in the southeast margin of Sichuan Basin. Both field outcrop observation and laboratory experimental results indicate: 1) the presence of framboidal pyrite; 2) δU ≥ 1; and 3) a negative δCe index anomaly. The detrital mineral properties and major element analyses indicate that the geotectonic background of the sediment sources for the Niutitang formation shale can be linked to the neritic zone and slope zone. The horizontal bedding indicates that suspended sediments were involved in the sedimentation. The Ba minerals, REE characteristics and trace element index (U/Th) demonstrate that most of the study area was formed in a normal sedimentary environment, but several isolated zones were affected by submarine hydrothermal sedimentation. The sedimentation of the Niutitang shale most likely occurred in a weak hydrodynamic, deep water, oxygen-deficient reducing environment. The major sediment sources were continental margins, such as the neritic and continental slope zones.

Tectonic Framework of Late Paleozoic Intrusions in Xingxingxia: Implications for Final Closure of South Tianshan Ocean in East Tianshan

AbstractThis work carried out systematic geological field investigation, petrography observation, zircon geochronology and whole rock geochemistry on Late Paleozoic intrusions in the Xingxingxia region near the Xinjiang‐Gansu provincial boundary, western China, aiming to constrain the Late Paleozoic tectonic framework of the Xingxingxia region and the final closure time of South Tianshan Ocean in the East Tianshan. The Xingxingxia area is located in the east part of the Tianshan orogen, and adjacent to the north of the Tarim Basin. The Late Paleozoic magma activities in the Xingxingxia region can be mainly divided into three stages. The first stage includes intrusive magma activities under a collision setting between Late Ordovician to the Late Devonian. The second stage is intrusive magma activities under a subduction setting during (304±3)–(278±3) Ma, and the third stage involves intrusive magma activities under a collision and post‐collision setting during (268±5)–(259.9±2.6) Ma. The final suture zone of South Tianshan Ocean should be between the Central Tianshan Block and South Tianshan accretionary complex. Based on previous work, both the first stage magma activities (i.e., intrusive magmatic activities between the Late Ordovician to Late Devonian) and the Hongliuhe ophiolitic complex indicate a close event between Central Tianshan Block and South Tianshan Accretionary Complex. The 304±3 Ma dioritic metamorphic gneiss of the XingXingxia complex and the 278±3 Ma diorite are all island arc calc‐alkaline rocks, the 289±3 Ma gabbro is island arc tholeiitic gabbro formed by magma from metasomatic enrichment mantle. All these results indicate that the second stage of magmatic activities is under a subduction setting. The third stage magma activities i.e. the granitic magma activities of (268±5)–(259.9±2.6) Ma occurred at a transitional setting from compressional to post‐collision extensional tectonic setting. Thus, around (268±5)–(260±3) Ma, the final closure of the South Tianshan Ocean occurred and the Tianshan orogen shifted into the intracontinental evolution stage. During and after the closure process, a wide range of metamorphism and large dextral strike‐slip faults developed.

산청 회장암복합체의 형성과정과 그 메커니즘

The study area is located in the western part of the Precambrian stock type of Sancheong anorthosite complex, the Jirisan province of the Yeongnam massif, in the southern part of the Korean Peninsula. We perform a detailed field geological investigation on the Sancheong anorthosite complex, and report the characteristics of lithofacies, occurrences, foliations, and research formation process and its mechanism of the Sancheong anorthosite complex. The Sancheong anorthosite complex is classified into massive and foliation types of Sancheong anorthosite (SA), Fe-Ti ore body (FTO), and mafic granulite (MG). Foliations are developed in the Sancheong anorthosite complex except the massif type of SA. The foliation type of SA, FTO, MG foliations are magmatic foliations which were formed in a not fully congealed state of SA from a result of the flow of FTO and MG melts and the kinematic interaction of SA blocks, and were continuously produced in the comagmatic differentiation. The Sancheong anorthosite complex is formed as the following sequence: the massive type of SA (a primary fractional crystallization of parental magmas under high pressure) the foliation type of SA [a secondary fractional crystallization of the plagioclase-rich crystal mushes (anorthositic magmas) primarily differentiated from parental magmas under low pressure]the FTO (an injection by filter pressing of the residual mafic magmas in the last differentiation stage of anorthositic magmas into the not fully congealed SA)the MG (a solidification of the finally residual mafic magmas). It indicates that the massive and foliation types of SA, the FTO, and the MG were not formed from the intrusion and differentiation of magmas which were different from each other in genesis and age but from the multiple fractionation and polybaric crystallization of the coeval and cogenetic magma.

Petrological properties and tectonic significance for Longyou garnet amphibolite

In view of the recent issue proposed by some researchers that “the garnet amphibolite in Longyou county of Zhejiang was retrograded from Caledonian collision-related eclogite”. Based on detailed field geological investigation, we carried out a systematic study including petrography, mineral chemistry, zircon geochronology and bulk rock geochemistry. Our results indicate that, the relatively small amounts of plagioclase which only found in interior of garnet or clinopyroxene metacryst are anorthite, while plagioclase that largely distribute in the outer part of garnet or clinopyroxene metacryst are andesine and labradorite (with their An value within 44–66), and no sodium-rich plagioclase (albite or oligoclase) which imply omphacite decomposition structure are found. The CL images of zircon exhibit obvious core-rim structure. U-Pb dating results indicate that the weighted average age of the zircon core part is 879±11 Ma, with Th/U ratio values ranging from 0.20–1.23 which suggest their magmatic origin; while the age of the rim is 446±5 Ma, and lots of their corresponding Th/U ratio show low values ( £ 0.1), suggesting their metamorphic origin. Moreover, the bulk rock geochemistry feature of garnet amphibolite suggest that its protolith is basic (the SiO2 content within 46.8%–48.2%), and its trace element exhibit E-MORB geochemical affinity. Based on the effective bulk rock composition and EPMA analysis results, as well as the mineral association we found, the P-T pseudosection for Longyou garnet amphibolite was worked out. And this figure reveals that the Longyou garnet amphibolite at least experienced three stages of metamorphism: the prograde metamorphism stage with P-T condition of 0.67–0.75 GPa/685–719°C; the peak-metamorphism with P-T condition of 0.91–0.97 GPa/766–782°C; and the retrograde metamorphism stage with P-T condition of ~0.68 GPa/~767°C (by traditional P-T thermobarometer, we also get a P-T condition of 0.66–0.67 GPa/720–740°C for retrograde metamorphism stage). Whichever stage, its pressure is medium-pressure but not high- pressure. In combination with regional geological setting, we prefer the following genetic model for Longyou garnet amphibolite: the paleo-South China Ocean subduction under Yantze plate in Neoproterozoic→trigger back-arc extension→mantle-derived magma upwelling and forming E-MORB type basic rocks in Neoproterozoic→medium to high-grade metamorphism in Silurian.

In situ Laser Induced Breakdown Spectroscopy as a tool to discriminate volcanic rocks and magmatic series, Iceland

This study evaluates the potentialities of a lab-made pLIBS (portable Laser-Induced Breakdown Spectroscopy) to sort volcanic rocks belonging to various magmatic series. An in-situ chemical analysis of 19 atomic lines, including Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Na, Si, Sr and Ti, from 21 sampled rocks was performed during a field exploration in Iceland. Iceland was chosen both for the various typologies of volcanic rocks and the rugged conditions in the field in order to test the sturdiness of the pLIPS. Elemental compositions were also measured using laboratory ICP-AES measurements on the same samples. Based on these latter results, which can be used to identify three different groups of volcanic rocks, a classification model was built in order to sort pLIBS data and to categorize unknown samples. Using a reliable statistical scheme applied to LIBS compositional data, the classification capability of the pLIBS system is clearly demonstrated (90–100% success rate). Although this prototype does not provide quantitative measurements, its use should be of particular interest for future geological field investigations.

Effects of freeze–thaw on the determination and application of parameters of slope rock mass in cold regions

Freeze–thaw could significantly affect the deterioration of mechanical properties of slope rock mass, and should be taken into consideration when determining the parameters of slope rock mass in cold regions. In this paper, we first measured the freeze–thaw coefficient using the freeze–thaw cycle test on intact slope rock mass from Mengku Mine, then determined the freeze–thaw correction coefficient by taking field geological investigation and rock hardness into consideration, and established a linear relationship between Geological Strength Index (GSI) and Tianshan slope rock mass rating (TSMR) system (a rock mass classification method applicable in cold regions) by incorporating the freeze–thaw correction coefficient into the expression of rock mass effect. The results show that freeze–thaw correction coefficient varies between 0.71 and 0.93, and GSI varies between 45 and 63. We further determined the parameters of slope rock mass by employing the generalized Hoek–Brown criterion and using it established a numerical rock slope excavation model and analyzed the rock mechanic features and stability status. The results indicate that the maximum ground deformation of slop rock mass is 15mm, and the floor rebound is about 42mm. Overall, the method described in the present paper can be used to select slope rock mass in cold regions and calculate the slope rock stability.

First evidence for ca. 780 Ma intra-plate magmatism and its implications for Neoproterozoic rifting of the North Yili Block and tectonic origin of the continental blocks in SW of Central Asia

The North Yili Block is one of the major continental constituents of the Central Asian Orogenic Belt (CAOB), study of its basement evolution and tectonic origin is essential for the understanding of the accretionary history of the CAOB and the reconstruction of global supercontinent as well. We conducted field geological, geochronological and geochemical investigations on the mafic dikes intruding in the highly deformed Proterozoic carbonate in the North Yili Block, NW Chinese Tianshan. Zircon U–Pb dating results suggest that the gabbro and gabbroic diorite dikes and associated granitic vein formed in 776–778Ma. Element and isotope geochemical data reveal that these intrusive rocks derived from an OIB-like mantle source, and were variably influenced by fraction crystallization and important crustal contamination, thus, a continental rifting setting is proposed for these dikes. Our new data provide the first evidence for a Neoproterozoic continental intra-plate magmatism occurred in the North Yili Block, this event can be linked with the coeval continental rifting-related magmatism in northern Tarim and in other microcontinents within the SW CAOB (e.g., Central Kazakhstan, Kyrgyzstan Middle Tianshan). Based on the comparison on the Neoproterozoic to early Paleozoic stratigraphic sequences between the North Yili and Tarim blocks, it is suggested that the North Yili Block most likely originated from the Tarim Block, and is potentially one additional constituent member of the Rodinia supercontinent.

Basin Framework and Basement Structuring of Lower Benue Trough, West Africa based on Regional Magnetic Field Data: Tectonic and Hydrocarbon Implications

Results from magnetic field modelling of the Lower Benue Trough, West Africa revealed thick sedimentation with maximum values in the neigbourhood of 7,000m-10,000m. This is in contrast to the average value of 5000m suggested by earlier studies. The thick sedimentation represent thermal sag which is a regional post-rift subsidence associated with West and Central Africa rift systems. N-S, NNW-SSE and E-W structural fabrics interpreted from the transformed magnetic data bound the trough. The subsurface magnetic models also revealed extended graben structures that form the major depoceters that are segmented by intrarift horsts and average crustal thickness of 22km. The qualitative interpretation comprising, analytic signal, directional derivatives and wavelength filtering in frequency domain and subsurface magnetic modelling show that the rift architecture/geometry is controlled by high angle faults and some sinistral transtensional movements that are predominant in the Benue rift system. The low mean anisotropic susceptibility (kb = -6.7x10-4 SI) correlating with the directional horizontal derivative (dy) of the magnetic field conform with the sinistral movement in the trough indicating that magnetic anomalies align themselves along fractures/faults/shear zones owing to their variations in physical properties. The characteristics/patterns of the magnetic anomaly wavelength and inferred results from earlier studies on geophysical potential field methods, geological investigation and physical parameters (susceptibility and remanence) obtained from the subsurface magnetic modelling are pointers to non-magmatic origin of the Lower Benue Trough. The basement structuring, basin framework and predominance of anisotropic susceptibilities (ka, kb and kc) in three orthogonal directions and remanence suggest tectonic setting in the trough due to Early Cretaceous opening of the South Atlantic Ocean and interplate movement in Africa. The grabens, half grabens, faults and deep sedimentation (depocenters) interpreted from the magnetic data are hydrocarbon related structural features.

Relief and palaeorelief analyses of the Kraków Spadzista Palaeolithic site as the tools used for explanation of the site location

The main research task was to explain the location of the Kraków Spadzista Gravettian site, based on the analyses of land relief and deposit lithology in the surroundings. Field geological (drilling and pit) investigations, geoelectric recognition, tachimetric geomorphological measurements, and geospatial analysis (GIS) were carried out in the site and its immediate vicinity. These investigations were supplemented with the IRSL dating of the cultural layer deposits, palaeosols, and loess. The obtained results indicate that the site was located in a depression of the karstified substratum (Jurassic limestones) filled with clay (Miocene) and loess (Pleistocene). Based on the results of geological and geophysical investigations, we reconstructed the palaeoform parameters, characterized its infilling, and documented spatial lithological variability of the deposits and the cultural layer. Gravettian material was discovered in two partially destroyed palaeosols. The lower one is a denuded initial interstadial soil, and the upper one is a complex solifluction cover composed of redeposited material, probably from a younger interstadial soil. Both units represent the younger part of the Interpleniglacial. The upper soil is buried by the continuous youngest loess layer, which covers the area of the archaeological site, completely covering the older relief.The eastern part of the Sowiniec horst, where the site's complex is situated, had a number of features useful for Palaeolithic settlement. It is a clearly distinguishable promontory, difficult to access almost from all sides. At the same time, it provided a good view for hunters, especially towards the Rudawa River valley. Features of mesoclimate, conditioned by relief, favoured the settlement.

Earthquakes and fault zone structure

The characterization of fault zone structure and its evolution is essential for understanding earthquake mechanics and rupture evolution. Most of our knowledge about fault structure is derived from field studies of ancient faults. By using earthquake locations, we reconstruct the complex structure of a normal fault at a resolution directly comparable with field geological investigations. At the surface conjugate sets of faults are connected with the main fault plane, which with depth shows bending and dilational jogs. Parallel slipping planes occur at the base of the seismogenic volume, and minor synthetic and antithetic structures are widespread. Fault zone thickness ranges from 0.5 to 1.5 km, while the damage density decays exponentially away from the fault plane, with values comparable to those observed on fault outcrops. The strong similarities between seismological and geological images of fault structure indicate that earthquakes have a key role in the evolution of fault architecture.

Epigenetic genesis and magmatic intrusion's control on the Dongguashan stratabound Cu–Au deposit, Tongling, China: Evidence from field geology and numerical modeling

The Dongguashan stratabound Cu–Au deposit in Tongling, Anhui is one of the largest Cu deposits in China. Its genesis is disputable, mainly skarn type (epigenetic origin) versus SEDEX type (syngenetic origin). In this paper, we present evidence from detailed field geological investigation and computational geodynamic modeling to support its epigenetic origin, and provide insights into its ore forming processes. The extremely irregular and sharp boundary of the orebodies and the presence of marble clasts in ores suggest that the ores were deposited from mineralizing fluids in tensile fracture zones and postdating the formation of the host rocks. The positive relation of the Cu grade and orebody thickness to the Qingshanjiao intrusion indicates the role of the magmatic intrusion in ore formation. The results of computational modeling demonstrate that the coupled mechano–thermo–hydrological processes during the syn-stretching cooling of the dioritic intrusion are critical for the formation and localization of the stratabound skarn orebody in the Dongguashan Cu deposit, and the magmatic intrusion must be an important constraint on the ore formation and localization of this deposit.

High-resistance controlled yielding supporting technique in deep-well oil shale roadways

In order to avoid the deep-well oil shale roadway being deformed, damaged, or difficult to maintain after excavating and supporting in Haishiwan coal mine, this paper has analyzed the characteristics of the deformed roadway and revealed its failure mechanism by taking comprehensively the methods of field geological investigation, displacement monitoring of surrounding rock, rock properties and hydration properties experiments and field application tests. Based on this work, the high-resistance controlled yielding supporting principle is proposed, which is: to “resist” by high pre-tightening force and high stiffness in the early stage, to “yield” by making use of the controlled deformation of a yielding tube in the middle stage, and to “fix” by applying total-section Gunite in the later stage. A high-resistance controlled yielding supporting technique of “high pre-tightening force yielding anchor bolt+small-bore pre-tightening force anchor cable+rebar ladder beam+rhombic metal mesh+lagging gunite” has been established, and industrial on site testing implemented. The practical results show that the high-resistance controlled yielding supporting technique can effectively control the large deformation and long-time rheology of deep-well oil shale roadways and can provide beneficial references for the maintenance of other con-generic roadways.

Detection of hidden faults beneath Khlong Marui fault zone using seismic reflection and 2-D electrical imaging

The Khlong Marui fault zone is a major fault located in the southern part of Thailand extending across the peninsula. In spite of the available information on fault segments and tectonic activity associated with faulting, the local scale fault characteristics are currently barely known and are often difficult to detect in areas where surface displacement has not occurred. The present geological field investigation reveals that the study area in Surat Thani province possibly contains more minor faults where the shallow faulting is evident. To detect fault locations and to study fault characteristics, seismic reflection analysis and 2-D electrical imaging were applied along the three survey lines as a case study. After data processing, an interpretation was proposed based on the correlation of geophysical results with the geological information. Discontinuities in the main horizons in seismic sections and correlatable zones in resistivity imaging indicate that faulting is present in a Permian-Carboniferous unit and may extend to the shallow subsurface in Quaternary sediments.

Prioritizing erosion-prone area through morphometric analysis: an RS and GIS perspective

The geomorphological characteristics of a watershed are more commonly used for developing the regional hydrological models for solving various hydrological problems of the ungauged watersheds in inadequate data situations. Therefore, in this study to find out the most vulnerable sub-watershed to soil erosion, morphometric analysis and prioritization were carried out on 14 sub-watersheds of Manot River catchment, which is a tributary of the Narmada River. The morphometric parameters considered for analysis are stream order, stream length, stream frequency, drainage density, texture ratio, form factor, circulatory ratio, elongation ratio, bifurcation ratio and compactness ratio. After analysis of morphometric parameters, compound parameter values are calculated and prioritization rating of 14 sub-watersheds is carried out. The sub-watershed 13 that has the lowest compound parameter value of 3.63 is likely to be subjected to maximum soil erosion; hence, it requires immediate attention to providing soil conservation measures. Morphological parameters-based prioritization is in good agreement with the geological field investigation carried out during the field work.

Stability analysis of a large landslide in hydropower engineering

This paper is devoted to stability analysis of the Zheng-Gang landslide in the Gu-Shui hydropower station in China. Based on the geological field investigations, the formation processes, the deformation mechanism related to rainfalls and the instability mode are first analyzed. Large scale direct shear tests on soils in the slip zone are performed in order to characterize influences of the content of particle and water on natural shear strength. Due to the difficulty to consider the lateral constrain and curvature effects of the bottom sliding surface, different three-dimensional models are established using the limit equilibrium method and the large strain Lagrange finite difference method. The results of stability analysis are in good agreement with the field observations. It is shown that the natural landslide is in a limit state and the creep deformation along the slipping surface is the main mechanism of landslide instability under in situ conditions.

Characteristics of Lead and Zinc Polymetallic Deposit and Wall Rock Alteration Zoning in Luziyuan, Yunnan

The lead and zinc polymetallic deposit in LuziYuan is an ultra-large type skarn deposit. The ore body originated from the interlayer crushed zone between the second and thrid section of stratum marble and slate (schist) interbedding of upper Cambrian series Shahechang group, the wall rock alteration is intensice in the diggings, and the alteration zoning is obvious. Through field geological investigation and data analysis, based on the petrography of alterated rocks and combined with catalog information of drilling, the wall rock alteration in the diggings of LuziYuan is divided into four alteration zones,which are in sequence: carbonate-quartz-chloritization zone; carbonate-quartz-skarn lithification zone; skarn-lead zinc ore mineralization zone; and skarn-pyritization zone. The forming of ore body is related to alterations such as skarn lithification, silicification, marmarization, magnetite, etc.

Field evidence of seismites in Quaternary deposits of the Jijel (Eastern Algeria) coastal region

Jijel has been hit by a strong earthquake in 1856 that triggered a destructive tsunami. Field geological investigations show that the marine terrace deposits (Tyrrhenian or likely Eutyrrhenian) exhibit several types of soft sediment deformation features including sismoslumps, thixotropic bowls, thixotropic wedges, and diapir-like structures. In addition, paleo-liquefaction features represented by neptunian and injection dikes have been observed in the sand dune deposits (Aterian or Wurm). Furthermore, typical paleo-earthquake-induced ground failures including lateral spreading, paleo-landslides, and sand volcanoes have been observed in recent, likely, Holocene deposits. Such features, remarkably comparable to present-day earthquake-induced ground failures showing clearly repetitive occurrence of past events may constitute a precious material for future paleo-seismic investigation. The various features have been interpreted herein as seismites associated to strong earthquakes produced likely by the potentially active faults previously identified in the area.