Western Limb Research Articles

Evolution of Characteristics of Vertical Electric Current and Magnetic Field in Active Regions of the Sun and their Relation to Powerful Flares

The study of evolution of magnetic field and electric currents in active regions of the Sun over a long-time interval is of interest for understanding the processes of accumulation and release of energy in them, leading to various phenomena that affect space weather. In this work, based on the photospheric vector magnetograms of the Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory, an analysis was made of the evolution of a number of characteristics of the magnetic field and vertical electric current in three active regions 11158, 11675, and 12673 that produced class M and X flares, during the time from their origin in the Eastern hemisphere, during the passage through the solar disk, and until the disappearance near the Western limb with a step of 2 hours. The characteristics under consideration included: the power-law exponent of the probability density function of the absolute value of the vertical electric current density, the maximum of the absolute value of the vertical current density, the signed and unsigned total vertical currents and the unsigned total vertical and horizontal magnetic fluxes, the energy of the nonlinear force-free and potential magnetic fields, the free magnetic energy, and the number of islands with strong vertical current. Some regularities in the behaviour of the characteristics under consideration are found, in particular regarding the occurrence of solar flares. The correlation coefficients between pairs of these characteristics are calculated. Additionally, M. Aschwanden’s approach is shown to be promising for predicting the maximum X-ray class of a flare based on the calculation of the energy of the potential magnetic field in active regions. The results obtained can be used to predict powerful solar flares.

Mineralogical Insights into PGM Recovery from Middle Group (1–4) Chromite Tailings

Variations in the recovery of platinum group metals (PGMs) are often attributed to mineralogical and other natural ore-type variations. To increase the recovery of PGMs by the flotation process, a comprehensive understanding of gangue and valuable minerals is essential for optimising the extraction and processing of metals. Recoveries may be improved if the questions of how, where, and why losses occur can be answered with a certain degree of confidence. A requirement is the availability of statistically reliable mineralogical data. The PGMs of MG-1–4 chromite tailings dumps of the western limb of the Bushveld complex (BC) were studied in detail to unravel the PGMs and the nature of the platinum group minerals in the sample. Characterisation of the chromite tailings via deportment analysis revealed that the sample contained a significant amount of 3E PGM + Au (Pt, Pd, Ru, and Au) and was concentrated in the -25 µm fraction. The results of automated mineralogical analysis showed that the sample was composed of the PGE-sulphides group, comprising 63.6 vol%, PGE-sulfarsenides 10.4 vol%, PGE-arsenides 1.3 vol%, PGE-bismuth tellurides 3.3 vol%, PGMs-alloy 4.1 vol%, and Laurite comprising 17.3 vol% of the total PGE population. The sample was composed of 66.5 vol% of liberated PGMs, 0.2 vol% attached to liberated BMS, 27.3 vol% of PGMs attached to or locked within silicate or oxide gangue composite particles, 0.2 vol% of PGMs associated with BMS attached to silicate or oxide gangue particles, and a low proportion (5.8 vol%) of PGMs reported being locked within gangue or oxide particles. The majority of PGM grains observed were reported in the fast-floating category (64.4 vol%), 27.6 vol% in the slow-floating 1 category, 2.2 vol% in the slow-floating 2 category, and 5.8 vol% to the non-floating category. The results of the study revealed that the PGMs of MG 1–4 chromite tailings were liberated; however, the low liberation index (<0.2) suggested that a significant portion of PGMs remained trapped within gangue, hindering their recovery. This highlights the need for effective comminution (crushing and grinding) to achieve better liberation. The sample contained fine particles that were more prone to being lost in the tailings and to lowering recovery due to the slimes coating valuable minerals. The recovery of the PGMs from this complex’s polymetallic bodies of low-grade and complex mineralogy will be insufficient with traditional methods and thus innovation is needed. Innovation like advanced comminution, novel flotation equipment or reagents, selective leaching and bioprocessing can overcome these challenges.

Magnetization related to late-Variscan extensional collapse in the Lugo Dome (NW Iberian Massif): a metamorphic petrology approach

The Eastern Galicia Magnetic Anomaly (EGMA) is one of the most distinctive and best studied magnetic anomalies in Iberia. It is located in NW Spain and overlaps the Variscan gneissic domes of Lugo and Sanabria. The Lugo Dome, in the north of the EGMA, deforms a large thrust sheet, the Mondoñedo Nappe, allowing the outcropping of its relative autochthon in the Xistral Tectonic Window, where extensional detachments resulting from late-Variscan tectonics crop out. A younger major detachment, the Viveiro Fault, developed on the western limb of the dome. Detailed ground-based magnetic mapping and geological charts show a clear spatial relationship between magnetic maxima and the extensional structures. Magnetic and paleomagnetic studies carried out on samples from this region indicate that rocks in the detachments commonly bear magnetite and hematite carrying induced but also remanent magnetizations and a very well-defined anisotropy of the magnetic susceptibility with directions matching those of the late-Variscan extensional fabrics.Three pairs of metasedimentary samples in equivalent structural positions display variously developed medium-pressure Barrovian parageneses attributed to the early compressional phases of the Variscan orogeny, and low-pressure Buchan-type parageneses associated with the late Variscan extension. Our phase diagram-based petrological study suggests that the non-magnetic samples preserve the Barrovian conditions of 560–640 °C, 5–8.7 kbar. The lithologically and structurally equivalent samples, originally non-magnetic, developed magnetite/hematite-bearing mineral assemblages during decompression and cooling to 500–620 °C, 1.5–6 kbar. This recrystallization was probably assisted by metasomatic oxidizing fluids. The induced component of magnetization is essentially carried by magnetite, while hematite seems the main carrier of remanence. These results support the existing cartographic, geophysical and paleomagnetic findings indicating that the magnetization in the Lugo Dome is related to late-Variscan extension.

GEOLOGY OF ALAKNANDA BHGIRATHI AND YAMUNA VALLEY, GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI & PAURI DISTRICTS, UTTRAKHAND STATE, INDIA

The Alaknanda is the trunk stream of Ganga system it drains the eastern part of the area of study .The rocks of Alaknanda valley and adjoining area consist of three units viz Central Cryastalline , Garhwal Group and Dudatoli Groups which from north to south are separated by thrust or fault. The Central Crystalline Group in this area consist of /comprises of northerly dipping sequence of Kyanite schist,Garnet mica schist quartzites and para amphibolites of Tugnath formation and it is intruded by granite at Ragsi,the main Central Thrust seprates it from Garhwal Group.The Dudatoli Groupis represented Pauri Phyllite and Kirsu Quartzite which forms the northern limb of Dudatoil syncline .The north Almora Thrust makes it boundary with Garhwal group. The later is divisiable in to Rudraprayga ,Lamri , Chamoli and Gawangarh and Patrali Formation which occurs in normal stratigraphic order. It is intruded by biotite granite by biotite graninte at Nainidevi and Mohankal , with tourmaline granite around Chirpatikhal and also by basic intrusive . The Rudraprayg , Lameri and Chamoli formations are equivalent to Uttarkashi Shyalnan and Nagnithhank Formation respectively in Bhagirathi valley. The Garhwal Group of has been subjected to three phases of tectonic deformation. The south east to southerly plunging folds such as Marithanasa and Pingapani synclines .Karanprayg anticline were developed during the second phase of movements. The Alaknada fault which cuts off set of the formation and earlier structures between Sunala is the strike slip fault in western part, appears to be the youngest elements. Geologically , the Bhagirathi valley and adjoining areas comprises of four distinct units namely from north to south the Central Crystalline Group , the Deoban Group the Simla Group,and Krol belt rock separating from one another by thrust or faults. The main Central Thrust passing through Sainj in northern part brings the northerly dipping crystalline rocks in sharp contact with under lying Deoban Group (Garhwal Group) sedimentries which comprises a lower Deoban Formation of Phyllite, slate meta basics, minor quartzite and lime stone, the middle Deoban formation of lime stone and upper Deoban formation of Quartzite and basics. The southern contact of Deoban Group is faulted one with comprising mainly siltstone, greywacks and slates dipping south .This fault called Sringar Nalupani fault of fundamental nature. In the southern and eastern part of the area this fault marks the contact between Deoban and Chandpur formation. In the western part south heading Ton Thrust separates the underlying Chanpur formation from the underlying Simla slates which shows abundant development of slump balls rod etc. indicating syndepositional disturbances in the basin of sedimentation while in Chanpur formation, is manly argillaceous, becoming arenaceous towards the top The Tons thrust passes through Laluli in Nagun Gad and is probably truncated by Tehri Nalupani fault at Chandpur in Bhagirathi valley. The full sequence of Krol rocks is exposed beautifully in Mussoorie syncline. The tectonic succession in Yamuna valley is Naogaon sheet comprising more metamorphosed rocks overly the Deoban group rocks separated from the latter by what is called the Naugaon thrust sheet which is folded in a North to Northwest plunging synform. The western limb of the folded thrust crosses Yamuna near the confluence with Kamola Gad and runs along the Kamola Gad. The rocks of the Naugaon sheet can be seen overlying the Deoban formation limestone along this section. The thrust hade towards east in this section. It follows a southerly trend till Tiyan when it takes an easterly swing, heading northward. It closes around Gair. The eastern limb of the synformal thrust sheet, heading westward crosses the Yamuna River at Kisna, Basic intrusive are seen along the thrust sheet near Kisna and around. The complexity of structural and tectonic set up in the area and lack of fossils make the task of correlation extremely difficult. However, on the basis of lithological similarities as well as structural disposition an attempt has been made to correlate the various litho units in the present area.

Seismic imaging of the complex geological structures in the southwestern edge of the Western limb, Bushveld Complex through focusing pre‐stack depth migration of legacy 2D seismic data

Seismic imaging of the complex geological structures in the southwestern edge of the Western limb, Bushveld Complex through focusing pre‐stack depth migration of legacy 2D seismic data

Transport of the Hunga volcanic aerosols inferred from Himawari-8/9 limb measurements

Abstract. The Hunga volcano (21.545° S, 178.393° E; also known as Hunga Tonga-Hunga Ha′apai) erupted on 15 January 2022, producing copious amounts of aerosols that reached high into the stratosphere, exceeding 30 km and settling into layers a few kilometres deep between 22 and 28 km. The Advanced Himawari Imager (AHI) on board the geostationary Himawari-8/9 platform at 140.7° E was able to monitor the eruption at 10 min intervals and 0.25 to 4 km2 spatial resolution within 16 spectral channels ranging from visible to infrared wavelengths and over a latitude–longitude field of view of ∼ ±75°. Here a new use of these data is proposed where the limb region of the field of view is exploited to detect aerosol layers extending vertically into the atmosphere. The analyses provide vertical profiles of scattered visible light and are compared to CALIOP space lidar measurements. Hunga aerosols are detected using the ratio of near-infrared reflectances at 1.61 and 2.25 µmm in the western limb from 22 January and in the eastern limb from 31 January 2022 up until the present time (December 2023). Between January and April 2022, the average zonal velocity is estimated to be ∼ −25 m s−1 (westwards) and the meridional velocity to be ∼ 0.2 m s−1 (northwards). The latitudinal spread is characterized by a gradual northerly movement of the main layer situated between 22 and 28 km in the first 60 d, and stagnation or slight southerly spread thereafter. There is a shallow maximum of the lower stratospheric aerosol between 10 and 20° S, and the aerosol loading during 2023 is elevated compared with the 3 months prior to the eruption. The Southern Hemisphere (0–30° S) tropical lower stratospheric aerosol e-folding time is estimated to be ∼ 12 months, but the decay is not uniform and has high variability. The current methodology does not provide quantitative estimates of the amount or type of aerosol, but based on the spectral properties of water and ice clouds the analysis suggests there is a strong liquid water content in the aerosol layers.

Impact of far-side structures observed by Solar Orbiter on coronal and heliospheric wind simulations

Context. Solar Orbiter is a new space observatory that provides unique capabilities to understand the heliosphere. In particular, it has made several observations of the far-side of the Sun and therefore provides unique information that can greatly improve space weather monitoring. Aims. In this study, we aim to quantify how the far-side data will affect simulations of the corona and the interplanetary medium, especially in the context of space weather forecasting. Methods. To do so, we focused on a time period with a single sunspot emerging on the far-side in February 2021. We used two different input magnetic maps for our models: one that includes the far-side active region and one that does not. We used three different coronal models typical of space weather modeling: a semi-empirical model (potential field source surface or PFSS) and two different magnetohydrodynamic models (Wind Predict and Wind Predict-AW). We compared all the models with both remote sensing and in situ observations in order to quantify the impact of the far-side active region on each solution. Results. We find that the inclusion of the far-side active region in the various models has a small local impact due to the limited amount of flux of the sunspot (at most 8% of the total map flux), which leads, for example, to coronal hole changes of around 7% for all models. Interestingly, there is a more global impact on the magnetic structure seen in the current sheet, with clear changes, for example, in the coronal hole boundaries visible in extreme ultra-violet (EUV) on the western limb, which is opposite to the active region and the limb most likely to be connected to Earth. For the Wind Predict-AW model, we demonstrate that the inclusion of the far-side data improves both the structure of the streamers and the connectivity to the spacecraft. Conclusions. In conclusion, the inclusion of a single far-side active region may have a small local effect with respect to the total magnetic flux, but it has global effects on the magnetic structure, and thus it must be taken into account to accurately describe the Sun-Earth connection. The flattening of the heliospheric current sheet for all models reveals that it causes an increase of the source surface height, which in return affects the open and closed magnetic field line distributions.

Structural Inheritance in the Eastern Cordillera, NW Argentina: Low‐Temperature Thermochronology of the Cianzo Basin

AbstractThe present‐day deformation style of the Eastern Cordillera in NW Argentina is strongly influenced by the inversion of pre‐existing Paleozoic and Mesozoic structures. In particular, the extensional faults and lithological contrasts resulting from the Cretaceous–Paleogene Salta Rift phase form heterogeneities that were preferentially reactivated during the Andean orogeny. Constraining the timing and characteristics of reactivation is a key to understanding the interplay between tectonics and inherited crustal anisotropies. In this study, we combine structural and sedimentological field data with a low‐temperature thermochronology data set from the area surrounding the fault‐bounded Cianzo basin. The southeastern boundary is formed by the inverted Hornocal fault, which was the basin‐bounding normal fault of the Lomas de Olmedo sub‐basin (Salta Rift basin). Lacustrine deposits of the Yacoraite Formation overspill on the footwall of this fault and mark tectonic quiescence during the post‐rift phase of the Salta Rift. Apatite (U‐Th‐Sm)/He and fission track ages in the Hornocal fault hanging wall show an onset of rapid cooling interpreted to be concomitant with fault inversion between the latest Oligocene and middle Miocene (∼24–15 Ma). Low‐temperature thermochronology data also constrain the timing of major folding in the eastern limb of the Cianzo syncline to pre‐10 Ma, whereas the western limb started tilting post‐10 Ma. Characterization of exhumation patterns related to fault activity surrounding the Cianzo basin emphasizes the influence of the pre‐existing structural framework on deformation in fold‐and‐thrust belts.

Digital elevation model‐based lineament analysis of the Zindapir anticline, Sulaiman fold‐and‐thrust belt, Pakistan

The N‐S oriented Zindapir anticline is an eastward verging mega‐structure (~130 km along and ~40 km across the strike) in the eastern Sulaiman fold‐and‐thrust belt on the western margin of the Indian Plate in Pakistan. In this study, we carried out a lineament analysis of the anticline based on shuttle radar topographic mission (SRTM) images and digital elevation model (DEM) data to demonstrate the application of this technique for modelling of the fractured reservoirs. We used shaded relief images, variations in the vertical exaggeration, sun and azimuth angles to enhance the DEM data and structures in the area. Stereographic projections indicated that the anticline is an upright, asymmetrical, gentle, doubly plunging and east‐vergent fold. The synthesized lineament map of the fractures indicates a total of 402 fractures across the Zindapir anticline. A total of 204 and 198 fractures were observed in the eastern and western limbs, respectively. Statistical analysis portrayed that the lineaments of the majority of fractures followed northwest‐southeast (NW‐SE) and west‐northwest—east‐southeast (WNW‐ESE) trends. These are oblique or transverse to the fold axis and could be interpreted as shear and tensional fractures related to drag and compression along the western boundary of the Indian Plate. Our study provides an example of lineament analysis for structural characterization and modelling of fractured reservoirs in a collision‐mountain setting.

Significant role of physical transport in the marine carbon monoxide (CO) cycle: observations in the East Sea (Sea of Japan), the western North Pacific, and the Bering Sea in summer

Abstract. The carbon monoxide (CO) in the marine boundary layer and in the surface waters and water column were measured along the western limb of the North Pacific from the Korean Peninsula to Alaska, USA, in summer 2012. The observation allows us to estimate the CO budgets in the surface mixed layer of the three distinct regimes: the East Sea (Sea of Japan) (ES), the Northwest Pacific (NP), and the Bering Sea (BS). CO photochemical production rates were 56(±15) µmol m−2 d−1, 27(±3) µmol m−2 d−1, and 26(±2) µmol m−2 d−1, while microbial consumption rates were 30(±8) µmol m−2 d−1, 24(±5) µmol m−2 d−1, and 63(±19) µmol m−2 d−1 in the ES, NP, and BS, respectively, both of which are the dominant components of the CO budget in the ocean. The other two known components, air–sea gas exchange and downward mixing, remained negligible (less than 3 µmol m−2 d−1) in all regimes. While the CO budget in the surface mixed layer of the NP was in balance, the CO production surpassed the consumption in the ES, and vice versa in the BS. The significant imbalances in the CO budget in the ES (25 ± 17 µmol m−2 d−1) and the BS (40 ± 19 µmol m−2 d−1) are suggested to be compensated by external physical transport such as lateral advection, subduction, or ventilation. Notably, the increase in the CO column burden correlated with the imbalance in the CO budget, highlighting the significant role of the physical transport in the marine CO cycles. Our observation, for the first time, underscores the potential importance of physical transport in driving CO dynamics in the marine environment.

Sub-Himalayan Mesozoic-Cenozoic tectonic-stratigraphic properties and deformation features in the western limb of Hazara Kashmir syntaxis, Pakistan

Sub-Himalayan Mesozoic-Cenozoic tectonic-stratigraphic properties and deformation features in the western limb of Hazara Kashmir syntaxis, Pakistan

Eruption of prominence initiated by loss of equilibrium: multipoint observations

ABSTRACT Using the SDO/AIA, SOHO/LASCO, STEREO/SECCHI, and ground-based H α, radio observations, we studied a prominence eruption (PE) from the western limb that occurred on 2013 December 4. PE is associated with a moderate coronal mass ejection (CME) and GOES class C4.7 flare. Before a couple of days, the prominence pre-existed as an inverse-S shaped filament lying above fragmented opposite polarities between two active regions. Initially, the prominence appears as kinked or writhed as observed from different vantage points. From a careful study of magnetic field observations, we infer that the flux emergence at one leg of the prominence causes the loss of equilibrium which then initiates the slow upward motion of the prominence followed by onset of the eruption at a projected height of 35 Mm. The fast rise motion is also in synchronization with the flare impulsive phase but the average acceleration is quite small (150 ms−2) compared to strong flare cases. In the LASCO field of view (FOV), the CME continues to accelerate at 3 ms−2 attaining a speed of 450 km s−1 at 16 R⊙. In the extended STEREO-A FOV upto 38 R⊙, the CME decelerates 0.82 m s−2. The PE launched type III bursts delayed by 14 min with respect to the flare peak time (04:58 UT). Since the prominence is lying in the fragmented polarities, it is likely that the sheared arcade has little contribution to the poloidal flux of the rising magnetic flux rope and subsequently weak flare is recorded. This study of PE emphasizes the influence of the magnetic reconnection on the CME speed, launch of type II, III burst, and the CME propagation distance farther away from the Sun.

Neodymium isotope variations in the Flatreef on Macalacaskop, northern limb, Bushveld Complex

The origin of the recently discovered Flatreef remains debated due to the pronounced interaction of the magmatic rocks with sedimentary floor rocks, resulting in a complex intrusive stratigraphy. In this study, we report new Nd isotopic compositions of Flatreef lithologies intersected by borehole UMT-393 on the farm Macalacaskop in order to improve our understanding of the magmatic history of the deposit and to further test the putative correlation between the Flatreef/Platreef and the Upper Critical Zone of the remainder of the Bushveld Complex. The initial epsilon Nd (εNdi) values for the Flatreef range between −5.2 and −7.6, overlapping with εNdi values of the Upper Critical Zone from the eastern (ranging between − 4.8 and − 8.5) and the Upper Critical Zone and Main Zone from the western limb (−6.3 and −7.6, and −6.3 and −7.4 respectively) of the Bushveld Complex. The Flatreef εNdi values also overlap with those of the Platreef; however, due to the varying footwall lithologies of the Platreef along strike, Platreef rocks display a wider variation in isotopic composition. Our findings support the correlation of the Flatreef with the Upper Critical Zone — Main Zone transition interval in the remainder of the Bushveld Complex, which includes the Merensky and Bastard reefs. Due to significant overlap between the εNdi values of the Flatreef and local potential contaminants occurring at the base of the Northern Limb, we propose that the Sr–Nd isotopic composition of the magmas that gave rise to the Flatreef are most likely attributable to the interaction of mantle-derived magma with upper and lower crustal rocks of the Kaapvaal Craton within a sub-Bushveld staging chamber, with possible syn- to post-emplacement modification as a result of interaction with dolomitic footwall rocks.

Effects of Coronal Magnetic Field Configuration on Particle Acceleration and Release during the Ground Level Enhancement Events in Solar Cycle 24

Ground level enhancements (GLEs) are extreme solar energetic particle (SEP) events that are of particular importance in space weather. In solar cycle 24, two GLEs were recorded on 2012 May 17 (GLE 71) and 2017 September 10 (GLE 72), respectively, using a range of advanced modern instruments. Here we conduct a comparative analysis of the two events by focusing on the effects of large-scale magnetic field configuration near active regions on particle acceleration and release. Although the active regions are both located near the western limb, temporal variations of SEP intensities and energy spectra measured in situ display different behaviors at early stages. By combining a potential field model, we find the coronal mass ejection (CME) in GLE 71 originated below the streamer belt, while in GLE 72 it originated near the edge of the streamer belt. We reconstruct the CME shock fronts with an ellipsoid model based on nearly simultaneous coronagraph images from multiple viewpoints and further derive the 3D shock geometry at the GLE onset. The highest-energy particles are primarily accelerated in the shock–streamer interaction regions, i.e., likely at the nose of the shock in GLE 71 and the eastern flank in GLE 72, due to quasi-perpendicular shock geometry and confinement of closed fields. Subsequently, they are released to the field lines connecting to near-Earth spacecraft when the shocks move through the streamer cusp region. This suggests that magnetic structures in the corona, especially shock–streamer interactions, may have played an important role in the acceleration and release of the highest-energy particles in the two events.

Groundwater Circulation in the Shallow Crystalline Aquifer of Tharisa Mine, South Africa: Evidence from Environmental Isotopes and Near-Surface Geophysics

For underground mining, efficient groundwater management is one of the critical mining economics components. The region of interest, known as Tharisa Mine, is situated on the western limb of the Bushveld Igneous Complex, which is home to South Africa’s premier platinum-group metal resources. This work aimed to provide the findings from the investigation and imaging of the near-subsurface hydrogeological architecture in a shallow profile using stable isotopes of water (18O and 2H) and radioactive water isotopes (3H). Regarding isotope data, 18O varied from −3.5 to 1.5‰; 2H from −24 to 4.7‰; and 3H from 2.0 to 3.4 T.U. Utilizing combined geophysical techniques, the results were verified. Additionally, the geophysical methods, including seismic refraction tomography, multichannel analysis of surface waves, electrical resistivity tomography, and magnetics, helped identify the fluid’s pathways and lineaments during migration to verify the isotope results. The groundwater inflow volumes into the open pit were initially determined by integrating the following findings: the delineation of fracture systems/zones and fluid migration pathways; mining activities enhance the storage and transmission ability of the aquifer; and the main sources of water in the mine include mixing of surface and deep water sources, recycling of water possibly via lineaments, and tailings dam seepages.

Active faults studies in Delhi and national capital region (NCR): Inferences from satellite data and field investigations

In recent years, the National Capital Region (NCR) of Delhi has experienced several earthquakes ranging in magnitude from 1.0 to 6.7. According to the last 50 years of earthquake data, the majority of earthquakes in the NCR have occurred near the Mahendragarh Dehradun Fault (MDF) and the Sohna Fault (SF). The region is bounded by a number of subsurface Ridges, Faults, and Lineaments, which are also influenced by the active plate boundary of the Indian and Eurasian plates. Active fault mapping is critical for the precise identification and marking of active fault traces in the NCR area for a precise seismic hazard assessment. We used high resolution Cartosat-1 stereopair data obtained from NRSC, Hyderabad, and Anaglyph (A 3D representation of the surface) and DEM prepared with ENVI software to map the active faults. We identified 12 sites in the NCR region based on satellite data interpretation, primarily along the MDF and Sohna Fault and their extensions. The presence of tectono-geomorphic markers along the MDF and Sohna Fault, such as warped surfaces indicative of fault scarps, stream offsets, gully erosion, and sag ponds, suggests active tectonic movement along these faults, most likely in the recent geological past. We believe the MDF is a right-lateral strike-slip fault with a compressional component on the western side and an extensional component on the eastern side. It acts as a segment boundary between compressional and extensional boundaries. We also identified the right lateral Nuh-Jhirka fault (NJF), which can be the Sohna Fault’s southern extension from Nuh to Jhirka. The western limb of the Delhi Mega fold has also seen a few right-lateral strike-slip movements that have extended up to the eastern bank of the Yamuna River, where the river reflects the base-level change and tight meandering on its upward side and a straight pattern on its downward side. This fault is known as the Delhi Fault (DF). The findings are preliminary, and further research would be required to create a detailed active fault map of the Delhi-NCR region to conduct a precise Seismic Hazard Assessment (SHA) of the region.

Localization patterns of gold mineralization in the Phuoc Son area, Central Vietnam

Background. In this paper, the authors aim to reveal the localization patterns of gold mineralization in the Phuok Son region of Central Vietnam, which formed a Proterozoic-Cambrian metamorphic complex in the zone of the Late Paleozoic Benzhang–Queshon granite block.Aim. To determine the localization patterns of gold mineralization in the Phuoc Son area, Central Vietnam.Materials and methods. The research was based on geological materials, as well as mine working and appraisal well data. The material composition of the materials was studied using 15 transparent sections and 18 polished sections. In total, 127 samples were subjected to atomic absorption spectroscopy.Results. Within the Phuoс Son gold ore field in Central Vietnam, the site of the Baidat and Baigo mines located in the zone of reverse-shear termination was investigated. Here, the gold ore bodies are represented by quartz-sulfide veins subparallel to schistosity. The ore-bearing zones are layered zones of tectonic faults, which formed at the end of the reverse-shear period and complicated the western limbs and locks of the anticlines. These zones were formed under regional sublatitudinal horizontal stresses. The horizons of carbonaceous quartz-sericite schists are of great importance in ore control. There are steeply dipping post-ore faults that displace ore bodies. Two gold mineralization stages can be distinguished. The early stage was characterized by a wide development of sphalerite and a smaller amount of gold. The later stage was associated with the main precipitation of gold and formation of galena. According to the geochronological data on the argon isotopy in biotite, the gold mineralization at Baidat and Baigo was probably formed in the Triassic (250–200 Ma ago), at the stage of extinction of the regional metamorphism of the Indosinian orogenyConclusion. The results obtained should be used when conducting local forecasting of gold deposits in Central Vietnam.

Rapid Rotation of an Erupting Prominence and the Associated Coronal Mass Ejection on 13 May 2013

In this paper, we report the multiwavelength observations of an erupting prominence and the associated coronal mass ejection (CME) on 13 May 2013. The event occurs behind the western limb in the field of view of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. The prominence is supported by a highly twisted magnetic flux rope and shows rapid rotation in the counterclockwise direction during the rising motion. The rotation of the prominence lasts for ∼ 47 minutes. The average period, angular speed, and linear speed are ∼ 806 sec, ∼ 0.46 rad min−1, and ∼ 355 km s−1, respectively. The total twist angle reaches ∼ 7 $\pi$ , which is considerably larger than the threshold for kink instability. Writhing motion during 17:42 – 17:46 UT is clearly observed by SWAP in 174 Å and Extreme-UltraViolet Imager (EUVI) on board the behind Solar Terrestrial Relations Observatory (STEREO) spacecraft in 304 Å after reaching an apparent height of ∼ 405 Mm. Therefore, the prominence eruption is most probably triggered by kink instability. A pair of conjugate flare ribbons and post-flare loops are created and observed by STA/EUVI. The onset time of writhing motion is consistent with the commencement of the impulsive phase of the related flare. The 3D morphology and positions of the associated CME are derived using the graduated cylindrical shell (GCS) modeling. The kinetic evolution of the reconstructed CME is divided into a slow-rise phase (∼ 330 km s−1) and a fast-rise phase (∼ 1005 km s−1) by the writhing motion. The edge-on angular width of the CME is a constant (60∘), while the face-on angular width increases from 96∘ to 114∘, indicating a lateral expansion. The latitude of the CME source region decreases slightly from ∼ 18∘ to ∼ 13∘, implying an equatorward deflection during propagation.

Stratigraphic variations in chromite chemistry through the UG-2 and UG-2E chromitites, bushveld igneous complex: implications for chromitite petrogenesis

ABSTRACT Chromitite petrogenesis in layered intrusions is important because some chromitites host economic Ni-Cu-platinum group element mineralization. Cryptic layering, which could be useful to reconstruct the chromitite origin, has been documented for some chromitites. Here, we document cm-scale stratigraphic profiles of the major and trace element contents in chromite across two chromitite seams from the Bushveld Igneous Complex. One set is from a massive UG-2 seam from the western limb, the other from a chromitite seam in the Turfspruit area of the northern limb, considered stratigraphically equivalent to the UG-2 (henceforth the ‘UG-2 equivalent’ or ‘UG-2E’). Stratigraphic profiles across the massive UG-2 only show a gradual increase in V contents (from bottom to top) and subtle variations in Mg#, Cr#, Mn, Zn, Co, Ti, and Ga contents. In contrast, the UG-2E profiles show significant variations in Mg# but not in Cr#, and distinct shifts in Mn, Zn, Co, Ni, Ti, and Ga contents and Fe3+/∑Fe values. These shifts correlate in part with variations in chromite abundance but also occur in sections as massive as the UG-2 reference. We argue that, in general, the presence of cryptic layering is more consistent with chromitite formation via gravitational settling or in situ crystallization rather than via slurries.

Diagnosing Limb Asymmetries in Hot and Ultrahot Jupiters with High-resolution Transmission Spectroscopy

Due to their likely tidally synchronized nature, (ultra)hot Jupiter atmospheres should experience strongly spatially heterogeneous instellation. The large irradiation contrast and resulting atmospheric circulation induce temperature and chemical gradients that can produce asymmetries across the eastern and western limbs of these atmospheres during transit. By observing an (ultra)hot Jupiter’s transmission spectrum at high spectral resolution, these asymmetries can be recovered—namely through net Doppler shifts originating from the exoplanet’s atmosphere yielded by cross-correlation analysis. Given the range of mechanisms at play, identifying the underlying cause of observed asymmetry is nontrivial. In this work, we explore sources and diagnostics of asymmetries in high-resolution cross-correlation spectroscopy of hot and ultrahot Jupiters using both parameterized and self-consistent atmospheric models. If an asymmetry is observed, we find that it can be difficult to attribute it to equilibrium chemistry gradients because many other processes can produce asymmetries. Identifying a molecule that is chemically stable over the temperature range of a planetary atmosphere can help establish a baseline to disentangle the various potential causes of limb asymmetries observed in other species. We identify CO as an ideal molecule, given its stability over nearly the entirety of the ultrahot Jupiter temperature range. Furthermore, we find that if limb asymmetry is due to morning terminator clouds, blueshifts for a number of species should decrease during transit. Finally, by comparing our forward models to those of Kesseli et al., we demonstrate that binning high-resolution spectra into two phase bins provides a desirable trade-off between maintaining signal to noise and resolving asymmetries.