Trending Faults Research Articles

Characterization of the accommodation zones along restraining and releasing bends from analogue modelling simulating the seagap fault, off-shore Tanzania

The study aims to understand geometry and evolution of accommodation zones along restraining and releasing bends in strike slip systems which is often complex and characterized by sharp change in polarity, resulting in a difficult characterization of traps location. A batch of sandbox modelling experiments was performed using a layered scaled sand material. The setup parameters of the wooden baseplates used in the first two experiments (SS1 and SS2) are basement offset of 6.5 cm/3 cm, 90°/90° stepovers in releasing and restraining bends of total 96 cm length and 25 cm width. The third experiment (SS3) was performed with basement offset of 6.5 cm/3 cm, 156°/126° stepovers in releasing and restraining bends of total 96 cm length and 25 cm width. The experiments were performed with special attention to the role of syn-kinematic sedimentation and the pre-existing structure of the basement. A sequence of pop-up and pull-apart structures was produced. Along the main structures, complex fault trend was compatible with a sinistral riedel distribution and a counterclockwise rotation of pre-existent elements. Change of fault's polarity at depth and dip direction flipping of high angle faults in accommodation zones were clearly observed. Even more, progressive propagation of the pop-up structures produces a spectacular inversion of adjacent extensional structures. Comparing results of the model with the Seagap fault zone, it is possible to put in evidence similar fault orientation and distribution. Internal structures developed were strongly influenced by syn-kinematic sedimentation as observed by characteristic helicoidal shape of growth faults. The analogue models clearly describe how boundary faults of the pull-apart basin along a paired bend, initially characterized by a normal kinematic can be subsequently inverted in the later stages, which can potentially have a strong impact on the petroleum system.

Research on thermal imaging fault detection system based on weibull distributed electrical system

A fault prediction analysis is performed In order to use infrared thermal imaging technology to detect electrical system faults, based on Weibull distribution technology. First, the principle is explained, the key technologies and factors of infrared thermal imaging and the electrical fault monitoring system are analyzed, and the available technologies are summarized. The detection process and analysis research are established with the help of on-site inspection and analysis results for power system fault analysis and research. The research shows that the method is effective for fault detection and trend analysis, and provides a reference for power fault detection and prediction analysis.

Structural architecture of the Middle Niger Basin, Nigeria based on aeromagnetic data: An example of a non-volcanic basin

The Middle Niger Basin is located within the west-central half of Nigeria, as a NW-SE trending Campano-Maastrichtian depo-centre which extends from the southern end of the Sokoto Basin west of Kainji reservoir southwestwards to the convergence of the Benue and Niger Rivers at Lokoja. The aeromagnetic anomaly data of the Middle Niger Basin was interpreted to characterize the structural architecture and depth to the magnetic basement of the basin. This is to expand the current knowledge of the region. The analysis of the data has been facilitated by the application of derivative and source parameter imaging techniques. The results from the application of total gradient to the aeromagnetic data provided here signify a rift origin of the basin and NW-SE trending fault systems in the surrounding basement complex terrain. The absence of magnetic highs on the first vertical derivative of the reduced-to-pole aeromagnetic data reveals lack of volcanic rocks within the sedimentary layers of the basin. Additionally, the consistent NW-SE trending source parameter imaging depth solutions within the basin confirm the internal geometry and NW-SE orientation of the basin with sediments not more than 1100 m thick.

Three-Dimensional Reservoir Modeling Based on Geostatistical Analysis to Determine Volumetric Oil in Place of Alpha Zone

The research of three-dimensional (3D) reservoir modeling of Alpha Zone is located in Balikpapan Formation Kutei Basin, East Kalimantan. The lithological analysis shows that Alpha Zone consists of sandstones, mudstone/shale and coal, which vertically and laterally distributed based on 206 wells and 3D seismic. Based on the results of petrophysical analysis, well and controlled correlation with seismic horizon picking, produced a pattern of fault trending NE-SW relative to the pattern trending anticline structure relative North-South, where the distributions of Alpha Zone have an average gross thickness of 9-15 meter and average net sandstone is 4-11 meter. Lithofacies approach method also used, which divided into three lithofacies sandstone, shale, and coal, which have sandstone facies distributions NW-SE, where the percentage of the distributions is 20%. The 3D reservoir modeling framework conducted is based on the reservoir depth structure maps generated from picking seismic and controlled by the correlation between wells. Distribution of reservoir properties include facies, Vshale, porosity, and water saturation (Sw), in making the property distribution is based on the analysis of the distribution wells using geostatistical variogram, where the results are validated against production data, so we will get an integrated 3D reservoir modeling of Alpha Zone. Furthermore, based on the volumetric determination of Original Oil in Place (OOIP) in Alpha Zone acquired 2.35 MMbbl.

Origin of the Kyaukmyet Low-Sulfidation Epithermal Gold Prospect, Monywa District, Central Myanmar

The Kyaukmyet prospect is one of the principal epithermal gold prospects in the Monywa District, Central Myanmar; its gold- and base metal-bearing quartz veins contain around 3 g/t gold. Ore minerals are mainly hosted by volcanic and volcaniclastic rocks of the Late Oligocene to Middle Miocene Magyigon Formation. The distribution of magmatic intrusions in the area is controlled by ENE-WSW trending faults; these faults are likely related to ore mineralization. Common ore minerals at the Kyaukmyet prospect include pyrite, sphalerite, galena, chalcopyrite, and electrum. They occur in mineralized crustiform-textured brecciated quartz veins and banded (colloform) and massive quartz veins. Mineralized rock is accompanied by silicification and propylitic and argillic alterations. The alteration mineral assemblages include quartz, adularia, calcite, chlorite, illite/smectite, sericite, and illite. Fluid inclusions in the quartz veins have homogenization temperatures ranging from 148 °C to 304 °C and salinities from 0.35 wt % to 2.75 wt % NaCl equiv. The quartz in the mineralized quartz veins was most likely precipitated at a depth ranges165-256 m below the paleosurface. The precipitation of gold at the Kyaukmyet prospect may have been formed by mixing large amounts of meteoric fluid with small amounts of magmatic fluid. The coexistence of liquid-rich and vapor-rich inclusions and presence of adularia and bladed calcite indicate that fluid boiling is caused the main mechanism of ore formation. The vein textures, ore mineral assemblages, alteration minerals and fluid inclusion data suggest that the Kyaukmyet prospect is a polymetallic low-sulfidation epithermal gold deposit.

Magnetotelluric investigation in the swarm prone intraplate Talala region of Saurashtra, Gujarat, western India

The Talala region of Saurashtra has experienced three moderate seismic events of magnitudes Mw5.0, Mw4.8 (on 6th November 2007), and Mw5.1 (on 20th October 2011) accompanied by swarms. The local earthquake data suggested two epicentral trends (ENE- WSW and NNW-SSE). The focal mechanism of all three earthquakes exhibit strike-slip mechanism with nodal planes sympathetic to these two trends. Based on low gravity values and ambiguous seismic reflections, the ENE-WSW trending fault was inferred and named as Girnar fault. The Magnetotelluric (MT) investigation has been carried out (i) to locate and characterize the Girnar fault and (ii) to ascertain the cause of seismicity in the region. The MT data is acquired along the ~62 km long NW-SE oriented profile, starting from the Sendarda village (NW) to the Hadmatiya village (SE) in the Junagadh district (Saurashtra), India. The regional strike of N19°E is obtained from the MT data. The data is subjected to 2D modeling and two conductors are identified along the profile, the first conductor is located between Ajeb and Aambalgadh village in the northern part of the profile with a resistivity range from 20 to 3500 Ohm.m and the second conductor is ~15 km south of the first conductor near Hirenvel village with a resistivity range from 50 to 3500 Ohm.m. The second conductor continues vertically down to 12–15 km depth and inferred as the Girnar fault. The shallow clustered seismicity (~5 km) near the second conductor advocates that it may be related to stresses induced by intense monsoon on the critically stressed Girnar fault, which has fractured the basement. The basement got fractured either from the local stress accumulation near the structural boundary or from the movement of the fluids to the less permeable crust.

High-Resolution 3D Seismic Imaging of Fault Interaction and Deformation Offshore San Onofre, California

The Inner California Borderland (ICB) records a middle Oligocene transition from subduction to microplate capture along the southern California and Baja coast. The closest nearshore fault system, the Newport-Inglewood/Rose Canyon (NIRC) fault complex is a dextral strike-slip system that extends primarily offshore approximately 120 km from San Diego to Newport Beach, California. Holocene slip rates along the NIRC are 1.5–2.0 mm/year in the south and 0.5 mm/year along its northern extent based on trenching and well data. High-resolution 3D seismic surveys of the NIRC fault system offshore of San Onofre were acquired to define fault interaction across a prominent strike-slip step-over. The step-over deformation results in transpression that structurally controls the width of the continental shelf in this region. Shallow coring on the shelf yields a range of sedimentation rates from 0.27–0.28 mm/year. Additionally, a series of smaller anticlines and synclines record subtle changes in fault trends along with small step-overs and secondary splay faults. Finally, sedimentary units onlapping and dammed by the anticline, place constraints on the onset of deformation of this section of the NIRC fault system. Thickness estimates and radiocarbon dating yield ages of 560,000 to 575,000 years before present for the onset of deformation.

Structural characterization of the Phitsanulok basin, onshore Thailand, and regional tectonic implications

The Phitsanulok basin is the largest onshore rift basin in Thailand and has been a major hydrocarbon producer for over 30 years. The basin formed in the mid-Cenozoic and was episodically reactivated after the early Miocene from nearby active tectonics, including the India-Asia collision. The basin is formed near a key tectonic transition between north and south Thailand between 16°N and 18°N. Previous studies recognized a north-south variation in structural styles across the Phitsanulok basin that may express deeper basement structures. The northern Phitsanulok basin is predominantly extensional whereas the southern basin shows unconformities, folding, and reverse faults from stronger inversion. Here we systematically characterize structural domains within the Phitsanulok basin from a basin-wide 2D and 3D petroleum industry seismic dataset and examine our observations within the context of regional tectonics. Our analysis includes time structure and isochron maps, spatial fault patterns, fault dip angles, fault throws, and fault azimuths. We find the most dramatic structural changes occur between the northern and southern Phitsanulok basin across 16°50′N latitudes. North of 16°50′N, the Phitsanulok basin has near-planar, steeply-dipping normal faults; arrays of low displacement, cross-cutting synthetic and antithetic extensional faults; and, a thickened and relatively undeformed Sukhothai depression that had up to 1700 ms two-way time (TWT) thickness (~2.3 km) between the Pliocene to Upper Early Miocene strata. In contrast, south of 16°50′N the basin has listric extensional faults; an abruptly thinner stratigraphic section (~400 ms TWT between the Pliocene to Upper Early Miocene strata; ~0.4 km), more gently-dipping faults, and larger fault throws. Our interpreted 16°50′N structural transition occurs near the southern limit of major earthquakes, changes in regional fault trends, and ENE-WSW magnetic lineaments and may highlight deep basement fabrics.

Tectonic controls on the salt diapir-related Mississippi Valley-type lead-zinc mineralization of Fej El Adoum ore deposit (Northern Tunisian Atlas): Constrains from detailed gravity and drill hole data

Relationship between salt domes and base metal mineralization is widely recognized across many salt-bearing basins (e.g., US Gulf Coast, Southern Europe and North Africa). In the northern Tunisian Atlas, the Mississippi Valley-type Fej El Adoum lead-zinc deposit represents one of these salt-related ore deposits. It consists of a combination of stratabound, veins, stockworks and cavity filling ore bodies, hosted by dolostone and limestone units, formed along the transition between Triassic evaporites and Cretaceous limestone.In the aim to better understand the concealed complex geological structures across the area, new-acquired detailed gravity data, constrained with field investigation and drill hole data were analyzed. Particularly, edge source detection techniques such as vertical gradient, total horizontal gradient and theta angle map were applied to outline structural contacts related to subsurface density variations. The main detected lineaments are in N–S, E-W and NW-SE directions. The N–S direction represents the deepest and most important lineament in direct contact with the evaporitic Triassic, while the transverse E-W direction is related to dextral strike-slip faults that subdivide the area into blocks. These major deeper lineaments have controlled the growth of the Triassic salt dome mainly during the Albo-Aptian as revealed by pinch outs of these series in direction of the crest of the structure. The detected lineaments seem to play a significant role in: (1) providing favorable pathways for the migration and ascent of mineralized fluids and (2) creating open space filling mainly at the interferences of N–S and E-W trending faults present at the contact between Triassic evaporitic unit and Cretaceous limestone. Our results suggest further reserves mainly in the E-W Ain Said occurrence and West of the Dar N'Hal closed mine.Our study also revealed the importance of structural study in the understanding of complex structures such as highly deformed salt dome cap rocks such as the Fej El Adoum diapiric structure.

Research on a method for diagnosing clogging faults and longitudinal axial flow in the threshing cylinders of drum harvesters

Here we present a high-precision method for predicting threshing drum clogging in drum harvesters, with strong applicability for longitudinal axial flow in crawlers. This method can be used to determine the alarm threshold. It entails placing a wireless vibration sensor at the outer end of the rotary shaft of the harvester to collect axial vibration signals from the drum to detect early fault characteristics. The method employs the Hilbert-Huang transform-analysis method to obtain time-frequency spectrum characteristics of the blocking process, thus diagnosing the speed reduction necessary to shut down when the threshing drum is clogged. The traditional method of extracting fault characteristic frequency by Fourier transform is compared with the proposed method. This method can not only diagnose the critical value of the rotating speed when the drum is clogged but also accurately and clearly reflect the trend of the drum clogging fault. The fault is within 3 standard deviations above or below the mean characteristic frequency, and abnormality is within 1 standard deviation above or below the mean characteristic frequency. Based on our experimental analysis, we introduce the concept of the confidence interval, andwe consider crop type and the diversity of working conditions. The proposed method improves the adaptability of forecasting to specific environments and combines agricultural machinery with agronomy. The trend of blocking can be predicted at least 1 s in the early stage of blockage by using a sliding window to process the vibration data collected in real time. This predictive ability makes the method superior to speed-sensor analysis in precision

Present-day movement trends of the major tectonic faults in the Sichuan-Yunnan region based on the constraint of GPS velocity fields

Based on the known fault distribution in Sichuan-Yunnan region (SYR), a rigid Euler rotation model is constructed by using GPS velocities (1998 ~ 2016) after excluding the stations near the fault boundaries and simultaneously a translation-rotation-strain model is constructed by using almost all GPS velocities to calculate three periods strain rate fields (2008.6 ~ 2010.4, 2010.5 ~ 2013.4 and 2013.5 ~ 2016.12) after Wenchuan earthquake. The results show that: (1) the strike-slip activity is the most common trends for the regional faults. The Xianshuihe-Xiaojiang fault, the Lancangjiang-Weixi-Weishan-Wuliangshan fault and the Longmenshan fault are the most active in the whole SYR, and the dislocation rate is more than 15 mm/a, and the trend of activity gradually decreases from the northwest to the southeast. (2) The different activity rates of the faults in the study area indicate that some of the eastward extrusion of the Tibet Plateau is absorbed and adjusted by the inside faults, and it is not a few large strike-slip faults. (3) Through the analysis of three periods’ grid velocity fields, we found that the movement rates of the Bitu section of Lanchangjiang fault, the Northwestern section of Weixi-Weishan fault and the Nujiang fault after Wenchuan earthquake are larger than that after Yushu and Ya’an earthquake, and the difference is about 8 mm/a. Besides, the activity rate of Northwestern section of Longmenshan fault after the Wenchuan earthquake is larger than that after the Ya’an earthquake, although the two epicentres distances are relatively close. (4) The strain rate fields and surface expansion rates show that the high value area is mainly distributed at or around the intersection among some fault zones and its surroundings, and the maximum area is mainly located at some long and deep fault zones such as the Longriba fault, the Longmenshan fault zone, the Ganzi-Yushu fault and the Xianshuihe, and the magnitude is about 35 ~ 50 nanstrain/a. The research should provide fundamental material for the study of crustal stress variation and earthquake prediction in Sichuan-Yunnan region.

Delineation of the Causative Fault of Recent Earthquakes (April-May 2020) in Delhi from Seismological and Morphometric Analysis

Recently, amid the pandemic of COVID-2019, the north-east Delhi region experienced two small earthquakes in a short span of 1 month; the first occurred on 12th April 2020 (Mw 3.5) and the other on 10th May 2020 (Mw 3.4). These events were followed by 4 aftershocks of magnitude Mw ≤ 3.0. We carried out morphotectonic (high stream length-gradient index) and static Coulomb stress failure analyses to delineate the hidden causative fault(s) in the region. In the study, ASTER DEM data of 30 m resolution and Survey of India (SoI) toposheets on 1:50,000 scales were used for morphotectonic analysis. The analysis depicted a very high stream length-gradient (SL) and fall in elevation in the epicentral area, suggesting the area to be tectonically active with a NE-SW trending fault line. In addition, the nature of static Coulomb failure stress contours for both the main events, Mw 3.5 and Mw 3.4, suggests an NNE-SSW trending high Coulomb stress regime. Such a high coulomb stress regime is obvious at the location where a high SL index and fall in elevation were marked, which clearly indicates the presence of NNE-SSW trending a causative fault, named ‘Khanpur-Japti fault’.

Incipient fault prediction based on generalised correntropy filtering for non-Gaussian stochastic systems

In this paper, the problem of incipient fault prediction is studied for the nonlinear stochastic system with non-Gaussian noises and actuator fault. The incipient fault is expressed as a nonlinear function with two unknown parameters (the occurring time of fault and the incipient fault evolution rate). Based on the generalised correntropy criterion, the fault detection filter is proposed, and then the occurring time of fault can be obtained. Once the fault is detected, the unknown fault evolution rate is estimated by designing a new generalised correntropy filter-based. According to the estimated fault occurrence time and the estimated fault evolution rate, the trend of incipient fault can be predicted. Finally, the simulation results of a single-link robotic flexible manipulator system are given to show that the proposed method is validated.

Voluminous Paleogene volcanism in the southern Mesa Central, Mexico: Unravelling the fissure-fed origin of rhyolitic ignimbrites of the Villa Garcia-Loreto Volcanic Complex

The southern portion of the Mesa Central (MC) physiographic province is covered by numerous Oligocene to Miocene volcanic successions that are part of the Sierra Madre Occidental silicic large igneous province. The MC merges with the Sierra Madre Occidental and the southern Basin and Range extensional province. The voluminous Villa Garcia-Loreto Volcanic Complex (VGLVC) is located in the southern portion of the MC and consists of predominantly rhyolitic lava flows, and voluminous products of explosive rhyolitic volcanism, mainly as lava-like to rheomorphic ignimbrite sheets. The volcanism in the area appears in two events, first, at 60.4 ± 0.3 Ma (K–Ar whole-rock age) with the fissure-fed eruption of an andesitic lava and second, with the fissure-fed eruption of two densely-welded, crystal-poor ignimbrites at 31.59 ± 0.14 Ma and 28.66 ± 0.07 Ma (40Ar–39Ar sanidine ages). Chondrite-normalized rare earth element patterns and primitive mantle normalized multi-element patterns show enrichment in light rare earth elements (LREE) and high field strength elements (HFSE). Geochemical analysis and mineral chemistry show that the andesitic magmas were generated by partial melting of the uppermost mantle in a subduction-related setting and ascended directly through the brittle crust and erupted along N-S trending faults. Rhyolitic magmas were generated by partial melting of the lower crust in an intra-plate and extensional setting, associated with an intense phase of the southern Basin and Range extension. During the ascent and storage in a shallow magma chamber fractional crystallization of mainly feldspars and pyroxene was the major process taking place in the evolution of the magma. Geophysical results suggest that the volcanic rocks of the VGLVC were originated by fissure-fed eruptions associated with the Loreto Graben fault. The major Basin and Range faults locally reach a depth of 7 km and trending in NNW-SSE direction. The combined results show that the Basin and Range extension favored the formation, ascent, and eruption of rhyolitic and andesitic magmas in the southern MC.

Late Pleistocene subglacial fissure-related volcanism at Caviahue-Copahue Volcanic Complex (37° 51° S, 71° 05’ W), South Volcanic Zone

The Caviahue-Copahue Volcanic Complex (CCVC, 37° 51’ S-71° 05′ W) is located in the central segment of the South Volcanic Zone, ~30 km eastward from the main Andean volcanic arc. Within a complex tectonic setting, it has developed under the influence of the northern transtensional Liquiñe-Ofqui Fault Zone, to the south and the Copahue-Antiñir Fault Zone to the northeast. The onset of volcanic activity within Caviahue volcano-tectonic depression has been dated at Ar/Ar 125 ± 9 ka and it is represented by lava flows and ignimbrites of Las Mellizas Formation. Copahue volcano has a very well documented historical eruptive record, encompassing 13 eruptive cycles in the last 260 years. On the contrary, volcano stratigraphy during Late Pleistocene and pre-historic times is poorly constrained, mainly due to the lack of reliable radiometric data. Based on the peculiar morphology and cooling-fracture systems, lavas that crop out along Dulce, Jara and NE Agrio river valleys have been included in a new stratigraphic unit, here named as Río Dulce Formation. A subglacial emplacement is proposed taking into account the evidence of ice-confinement, provided by the flat-topped and steep-sided lava domes/flows and dammed lava flows. In addition, melt water-magma interaction is supported by conspicuous fine columnar-jointing and closely spaced curved bands with plumose structures, well-developed pseudopillow fracture systems, platy and hackly fractures and cube-jointed entablature-bearing lava flows. The basaltic andesites (SiO2= 55–57%) are porphyritic, with ~30–40% of sieved plagioclase, two pyroxenes and olivine, set in a glassy groundmass. Lava vent distribution and primary anisotropy planes orientation, in coincidence with WNW-ESE and NE-SW trending faults, lineaments and fault scarps, document a first-order structural control on the volcanic emplacement. Although undated, this study can contribute to understanding the timing of glacial fluctuations during Late Pleistocene. Furthermore, it has implications on hazard assessment since it highlights that the evolution of the CCVC has experienced alternating fissure and central eruptive style, likely related to the dynamics of the magma-plumbing system, as suggested by geophysical evidence of unrest.

Net right-lateral slip of the Eastern Frontal Fault System, North Andes Sliver, northwestern South America

The NNE-directed tectonic escape of the North Andean block (NAB) or sliver (NAS) with respect to South America (SA) is generally accepted now. NAS is detached from continental South America (SA) by a 2000-km-long, NE-SW-trending dominant dextral fault system, known as the Eastern Frontal Front System (EFFS; Pennington's name and acronym kept for simplicity) that extends from the gulf of Guayaquil-Tumbes basin (GGTB) in offshore Ecuador to the Caribbean coasts of Venezuela in the Golfo Triste region. From SW to NE, EFFS comprises the following fault systems: In Ecuador, Puná-Pallatanga-Cosangá-Chingual (CCPP); In Colombia, Afiladores, Sibundoy, Algeciras and Guaicáramo; and in Venezuela, Boconó (BF).Several estimates of total dextral slip have been calculated along the EFFS. In Ecuador, the Pallatanga fault (part of the CCPP) displaces several large geologic and morphologic units in about 10 km. The net slip of EFFS at this western front of the Western cordillera can be as much as the double (≈20 km) if strain happens to be distributed between sub-parallel faults. Further south, at the very southern tip of the EFFS, from seismic data acquired from the GGTB, an estimate of 13.5–20 km of lengthening of this basin from the Plio-Quaternary boundary has been proposed.In Colombia, the Algeciras lazy Z-shaped pull-apart basin (Huila Dpt.) provides another estimate. The extent of the Quaternary basin fill measured along the regional fault trend on SGC geologic plate 345, is about 10 km. This is a minimum estimate because the fault shortcuts the basin in more recent times, increasing such slip in at least about 1–2 km. In Venezuela, although more reliable and frequent dextral offsets are of the order of 30 km, a larger 70–80 km offset in Mesozoic rocks was once proposed across BF. A supportive argument to the 30 km net slip along the Mérida Andes axis may be derived from a present mismatch of Bouguer anomaly minima between both adjacent flexural basins of no more than 40 km.From all the estimates of total slip here compiled along EFFS, we can conclude that the NE tectonic escape of NAS is most likely not larger than 30–35 km. This net slip may vary along EFFS strike, being smaller (close to 20 km) in the south. Therefore, despite the large size of NAS, its escape remains modest at plate scale. Remarkably, EFFS net slip is in the same order of magnitude as the ≈20 km for the Sumatra fault, which is as long as the EFFS (≈1900 km long).

Aero-engine Gas Path Performance Degradation Assessment Based on a Multi-objective Optimized Discrete Feedback Network

In order to solve the problem of neural network algorithm for aero-engine’s gas path performance evaluation under high-dimensional evaluation index with non-equal weights, the trend analysis method and fault fingerprints are used to mine engine’s gas path performance characteristic parameters. A comprehensive weighting method based on game theory is proposed to optimize the weight value of each gas path performance characteristic parameter. A discrete feedback neural network with single-layer and binary output is established. The original gas path performance evaluation index is equivalently expanded according to the weight ratio, and the gas path state evaluation indexes with different weights are mapped into higher-dimensional equivalent evaluation indexes with equal weights. The network attractor is designed according to the engine gas path performance evaluation levels, and the design of discrete feedback neural network weights is transformed into multi-objective programming problem, and a particle swarm optimization algorithm with adaptive inertia weight is used to improve the efficiency and global search ability of particle swarm optimization. The experimental results shows that the proposed model and algorithm can provide a scientific and reasonable machine learning method for the evaluation of high-dimensional evaluation index with non-equal weights.

Multiple isotope (He-Ar-Zn-Sr-Nd-Pb) constraints on the genesis of the Jiawula Pb-Zn-Ag deposit, NE China

• Mantle fluid and atmospheric water are two most important sources for the ore-forming fluid of the Jiawula deposit. • Zn isotopic variation was most likely caused by kinetic Rayleigh fractionation. • Coeval magma played a key role in the formation of the deposit. The large Jiawula Pb-Zn-Ag deposit is located in the Manzhouli area, northeast China. The Pb-Zn-polymetallic mineralization in the Jiawula deposit is present as ore veins distributed in Early Mesozoic sedimentary and magmatic rocks and was controlled by NWW to NNW trending faults. He and Ar isotope analysis results of fluid inclusions hosted in pyrite show that 40 Ar/ 36 Ar ratios are 280.5–300.1, which is close to the atmospheric value (295.5). 3 He/ 4 He ratios vary from 40.15 × 10 −7 to 71.68 × 10 −7 . The calculated mantle He are in a range of 35.8–64.0%, with an average of 51.0%. He-Ar isotopic data reveals that the ore-forming fluids of the Jiawula deposit were derived from mixture of two fluid end-members: (1) mantle-derived fluid, which has provided a considerable proportion of He; and (2) crustal fluid, which is characterized by almost atmospheric Ar and crustal He. The sphalerite from the Jiawula deposit have a narrow range of δ 66 Zn JMC values, varying from 0.15 to 0.307‰, with a mean value of 0.236‰. We suggest that the variation of Zn isotope values of sphalerite from the Jiawula deposit was most likely caused by kinetic Rayleigh fractionation. The Zn isotope analysis result, combined with previous S isotopic data, indicate that the ore-forming material of the Jiawula deposit was derived from a single source. The intrusive rocks in the deposit have low initial 87 Sr/ 86 Sr ratios, relatively high ε Nd (t) values, and young T DM2 Nd model ages, indicating a high proportion of juvenile material in the petrogenesis. Combined with Sr-Nd-Pb isotopic data of intrusive rocks that are coeval with mineralization in the deposit, He-Ar-Zn isotope analysis results, and previous studies, we propose that the mantle component in the ore-forming fluid and material of the Jiawula deposit was most probably derived from the simultaneous magma, which was derived from partial melting of crust with involvement of mantle magma in an extensional setting during the late Jurassic to the early Early Cretaceous.

Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (207Pb/204Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO2), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II.

Trace element contamination in the mine-affected stream sediments of Oued Rarai in north-western Tunisia: a river basin scale assessment

High-quality and accurate environmental investigations are essential for the evaluation of contamination and subsequent decision-making processes. A combination of environmental geochemical indices, multivariate analyses and geographic information system approach was successfully used to assess contamination status and source apportionment of trace elements (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, V and Zn) in surface stream sediments from the Oued Rarai basin in north-western Tunisia, containing various metal and metalloid ores. The contamination level reported in this study indicates a non-negligible potential ecological risk, mainly related to sediment transport along the river. Antimony (concentrations ranged from 0.02 to 297 mg kg−1 and Igeo > 5), arsenic (from 0.5 to 1490 mg kg−1 and Igeo > 5), lead (from 2.9 to 5150 mg kg−1 and Igeo > 5) mercury (from 0.05 to 54.4 mg kg−1 and Igeo > 5) and silver (from 0.05 to 9.4 mg kg−1 and Igeo > 5) showed the most crucial contamination. Besides, potential ecological risk index values were maximum for arsenic with a median of 302, indicating a very high to serious ecological risk (> 160). Results from correlation analysis and principal component analysis revealed three main geochemical associations related to lithologic, tectonic and anthropogenic sources. V, Cr and Cu mainly originated from natural bedrock and soil. Ag and Cd were more controlled by both natural and mining enrichments. Mercury and Pb were mostly influenced by the ancient ore-related activities at the Oued Rarai site and north-east–south-west trending faults. Finally, Sb, As, Ni and Zn were largely controlled by the siliciclastic continental Neogene sequences. Finally, the physical and chemical dynamics of the watershed system, lithological properties, mineralisation, tectonic settings and mobilisation of subsurface sediments largely controlled both concentrations and spatial patterns of trace elements in the study basin. These results need to be considered in the strategies of suitable environmental management at former and current mining sites in north-western Tunisia.