A New Approach in Coal Mine Exploration Using Cosmic Ray Muons

Muon radiography is a technique that uses cosmic ray muons to image the interior of large scale geological structures. The muon absorption in matter is the most important parameter in cosmic ray muon radiography. Cosmic ray muon radiography is similar to X-ray radiography. The main aim in this survey is the simulation of the muon radiography for exploration of mines. So, the production source, tracking, and detection of cosmic ray muons were simulated by MCNPX code. For this purpose, the input data of the source card in MCNPX code were extracted from the muon energy spectrum at sea level. In addition, the other input data such as average density and thickness of layers that were used in this code are the measured data from Pabdana (Kerman, Iran) coal mines. The average thickness and density of these layers in the coal mines are from 2 to 4 m and 1.3 gr/c³, respectively. To increase the spatial resolution, a detector was placed inside the mountain. The results indicated that using this approach, the layers with minimum thickness about 2.5 m can be identified.     

Shallow sediment transport flow computation using time-varying sediment adaptation length

Based on the common approach,the adaptation length in sediment transport is normally estimated astemporally independent.However,this approach might not be theoretically justified as the process of reaching the sediment transport equilibrium stage is affected by the flow conditions in time,especially for fast moving flows,such as scour-hole developing flows.In this study,the two-dimensional（2D） shallow water formulation together with a sediment continuity-concentration（SCC） model were applied to flow with mobile sediment boundary.A timevarying approach was proposed to determine the sediment transport adaptation length to simulate the sediment erosion-deposition rate.The proposed computational model was based on the Finite Volume（FV） method.The Monotone Upwind Scheme of Conservative Laws（MUSCL）-Hancock scheme was used with the Harten Lax van Leer-contact（HLLC） approximate Riemann solver to discretize the FV model.In the flow applications of this paper,a highly discontinuous dam-break,fast sediment transport flow was used to calibrate the proposed timevarying sediment adaptation length model.Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in the literature,i.e.a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow.Good agreement with the experimental data were obtained with the proposed model simulations.The tests prove that the proposed model,which was calibrated by the discontinuous dam-break bed scouring flow,also performed well to represent rapid bed change and steady sediment mobility conditions.     

Seismo-stratigraphic and structural interpretation of seismic data of Titas gas field,Bengal basin,Bangladesh

In the present study, seismic interpretation has been carried out over Titas structure of Bengal basin, Bangladesh to figure out its seismo-stratigraphic and structural behavior. Seven well marked reflecting horizons (R-01 to R-07) have been identified within the Neogene sedimentary sequences using 18 seismic sections and well log data. A new seismic stratigraphy of Neogene sequences has been proposed for the Titas structure ruling out the traditional lithostratigraphy. The studied structure has been divided into 3 megasequences (MS1, MS2 and MS3). Reflector R-01 and R-03 represent the tops of the megasequence 2 (MS2) and megasequence 1 (MS1) respectively. These well marked reflectors are correlated with the top of the traditional litho-groups called Tipam and Surma. Reflectors R-02 and R-04 represent acoustic impedance boundaries within MS2 and MS1 due to lithological gradation. However, R-02 and R-04 are not considered as sequence/ formation boundaries because geologically these are not well defined. Reflectors R-05, R-06 and R-07 represent top of the gasbearing zones A, B and C that belongs to MS1. All these interfaces or reflectors are anti-form with a central long crestal zone. It forms a north-south trending semi-domal sub-surface anticlinal structure having a semi-dome shaped closure. The structure is asymmetric with steeper eastern flank and gentler western flank. The crestal region is essentially plain with discontinuous reflection. The semidomal nature of the anticline is in contrast to the neighboring narrow anticlines. Structural pattern suggests its development in relation to the NE-SW trending stress field due to convergence of Indian plate with Burmese plate. Structures of the shallower and deeper reflectors are formed at different phases of structural development.     

Recharge mechanism and processes controlling groundwater chemistry in a Precambrian sedimentary terrain: a case study from Central India

Unplanned and unsustainable extraction has created stress on groundwater resources in many parts of India. The stress symptoms are more pronounced in hard rock areas, where the aquifer potentials are comparatively low. Present research targeted an area of 3000 km² in the interstream region between the Kharun and Seonath rivers, which is one such region in Central India. In spite of being a water-stressed area, so far, little is understood about processes of recharge, amount of recharge and processes controlling chemical quality, which are key inputs for groundwater management in the area. This study presents an appraisal of recharge mechanism, recharge rate and prevailing water–rock interactions in the study area. Stable isotope composition of groundwater when compared to that of rainfall indicates monsoon rainfall as the primary source of groundwater recharge. Winter rains, which are characteristically enriched in heavier isotopes, do not contribute notably to groundwater recharge. Recharge is rapid with minor or no evaporative enrichment before recharge. Further, analysis of stable isotopes show that ‘macropore recharge’ is dominant in limestone or calcareous shale, covering more than 70% of the study area. Also apparent is the vertical connectivity amongst the aquifers. However, active intermixing of surface water and groundwater is not a predominant process. Annual groundwater recharge from rainfall, as derived from chloride mass balance, is 105.26 million cubic metre. Groundwater is predominantly of bicarbonate type, irrespective of its hydrostratigraphic (lithology) setting. Dissolution of carbonates and gypsum (occurring as veins), weathering of feldspar and ion exchange of clay minerals are amongst the most likely processes controlling the regional groundwater chemistry.     

Propagation of Coronal Mass Ejections Observed During the Rising Phase of Solar Cycle 24

In this study, we investigate the interplanetary consequences and travel time details of 58 coronal mass ejections (CMEs) in the Sun–Earth distance. The CMEs considered are halo and partial halo events of width \({>}\,120\)°. These CMEs occurred during 2009?–?2013, in the ascending phase of the Solar Cycle 24. Moreover, they are Earth-directed events that originated close to the centre of the solar disk (within about \(\pm30\)° from the Sun’s centre) and propagated approximately along the Sun–Earth line. For each CME, the onset time and the initial speed have been estimated from the white-light images observed by the LASCO coronagraphs onboard the SOHO space mission. These CMEs cover an initial speed range of \({\sim}\,260\,\mbox{--}\,2700~\mbox{km}\,\mbox{s}^{-1}\). For these CMEs, the associated interplanetary shocks (IP shocks) and interplanetary CMEs (ICMEs) at the near-Earth environment have been identified from in-situ solar wind measurements available at the OMNI data base. Most of these events have been associated with moderate to intense IP shocks. However, these events have caused only weak to moderate geomagnetic storms in the Earth’s magnetosphere. The relationship of the travel time with the initial speed of the CME has been compared with the observations made in the previous Cycle 23, during 1996?–?2004. In the present study, for a given initial speed of the CME, the travel time and the speed at 1 AU suggest that the CME was most likely not much affected by the drag caused by the slow-speed dominated heliosphere. Additionally, the weak geomagnetic storms and moderate IP shocks associated with the current set of Earth-directed CMEs indicate magnetically weak CME events of Cycle 24. The magnetic energy that is available to propagate CME and cause geomagnetic storm could be significantly low.     

Group velocity dispersion analysis in northern Peninsular Malaysia

The crustal structure beneath three seismic stations over Malaysia has been investigated with the application of the group velocity dispersion analysis of the northern Sumatra earthquake data which occurred on 06 April 2010. Eighteen crustal layer models are constructed to assess the structure. Group velocity dispersions have been computed for the recorded earthquake data using a graphical method and modified Haskell matrix method for the models. Both dispersions have been presented for the interpretation of crustal layers. Findings have shown four major crustal layers having thicknesses of 2.5–4.0, 2.0–5.5, 5.0–8.0, and 8.5–9.0 km, while in Terengganu, it has shown three layers. Density, shear, and compressional wave velocities used in models have suggested that the crustal structure of the northern part of Peninsular Malaysia is crystalline. Major crustal minerals are of quartz, plagioclase, and mica. Most layers seem to have upward directions toward Perak from Kedah and Terengganu.     

Impact analysis of climate change on Kolahoi Glacier in Liddar Valley,north-western Himalayas

Glaciers are among the most conspicuous and dynamic features on the earth’s surface and are also highly sensitive to changes in climatic parameters. Glaciers in the Kashmir Himalayas have been reported to be retreating due to climate forcing. Kolahoi Glacier is one of the largest and important glaciers of the Kashmir Himalayas and is the main source of Liddar River, which is the largest tributary of the Jhelum River system. In the present study, an analysis to assess the response of Kolahoi Glacier to the changing climate was carried out using the Survey of India (SoI) map and multi-temporal Landsat satellite data. The results show a significant change in the spatial extent of Kolahoi Glacier. The total area of this glacier has reduced from 12.21 km² in 1962 to 11.61 km² in 2010. An analysis of meteorological data (temperature and precipitation) shows that the average annual temperature increased from 9.1 °C in 1980–1989 to 10.3 °C in 2000–2009, while the precipitation decreased from 1329.44 to 1126.89 mm during the same period. The results suggest that this glacier will be annihilated completely if the same retreating trend continues.     

Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea,northeastern Indian Ocean

The aragonite compensation depth (ACD) fluctuated considerably during the last glacial until the Holocene with a dominant pteropod preservation spike during the deglacial period, which is prominently seen in three well‐dated cores covering the Andaman Sea, northeastern Indian Ocean. The precise time period of the preservation spike of pteropods is not known but this knowledge is crucial for stratigraphical correlation and also for understanding the driving mechanism. Isotopic and foraminiferal proxies were used to decipher the possible mechanism for pteropods preservation in the Andaman Sea. The poor preservation/absence of pteropods during the Holocene in the Andaman Sea may have implications for ocean acidification, driven by enhanced atmospheric CO₂ concentration. Strengthening of the summer monsoon and the resultant high biological productivity may also have played a role in the poor preservation of pteropods. The deglacial pteropod spike is characterized by high abundance/preservation of the pteropods between ～19 and 15 cal. ka BP, associated with very low atmospheric CO₂ concentration. Isotope data suggest the prevalence of a glacial environment with reduced sea surface temperature, upwelling and enhanced salinity during the pteropod preservation spike. Total planktic foraminifera and Globigerina bulloides abundances are low during this period, implying a weakened summer monsoon and reduced foraminiferal productivity. Based on the preservation record of pteropods, it is inferred that the ACD was probably deepest (>2900 m) at 16.5 cal. ka BP. The synchronous regional occurrence of the pteropod preservation spike in the Andaman Sea and in the northwestern Indian Ocean could potentially be employed as a stratigraphic marker.     

Oriented growth of garnet by topotactic reactions and epitaxy in high‐pressure,mafic garnet granulite formed by dehydration melting of metastable hornblende‐gabbronorite (Jijal Complex,Kohistan Complex,north Pakistan)

Garnet growth in high‐pressure, mafic garnet granulites formed by dehydration melting of hornblende‐gabbronorite protoliths in the Jijal complex (Kohistan palaeo‐island arc complex, north Pakistan) was investigated through a microstructural EBSD‐SEM and HRTEM study. Composite samples preserve a sharp transition in which the low‐pressure precursor is replaced by garnet through a millimetre‐sized reaction front. A magmatic foliation in the gabbronorite is defined by mafic‐rich layering, with an associated magmatic lineation defined by the shape‐preferred orientation (SPO) of mafic clusters composed of orthopyroxene (Opx), clinopyroxene (Cpx), amphibole (Amp) and oxides. The shape of the reaction front is convoluted and oblique to the magmatic layering. Opx, Amp and, to a lesser extent, Cpx show a strong lattice‐preferred orientation (LPO) characterized by an alignment of [001] axes parallel to the magmatic lineation in the precursor hornblende‐gabbronorite. Product garnet (Grt) also displays a strong LPO. Two of the four 〈111〉 axes are within the magmatic foliation plane and the density maximum is subparallel to the precursor magmatic lineation. The crystallographic relationship 〈111〉_Grt // [001]_Opx,Cpx,Amp deduced from the LPO was confirmed by TEM observations. The sharp and discontinuous modal and compositional variations observed at the reaction front attest to the kinetic inhibition of prograde solid‐state reactions predicted by equilibrium‐phase diagrams. The P–T field for the equilibration of Jijal garnet granulites shows that the reaction affinities are 5–10 kJ mol.^?1 for the Grt‐in reaction and 0–5 kJ mol.^?1 for the Opx‐out reaction. Petrographic and textural observations indicate that garnet first nucleated on amphibole at the rims of mafic clusters; this topotactic replacement resulted in a strong LPO of garnet. Once the amphibole was consumed in the reaction, the parallelism of [001] axes of the mafic‐phase reactants favoured the growth of garnet crystals with similar orientations over a pyroxene substrate. These aggregates eventually sintered into single‐crystal garnet. In the absence of deformation, the orientation of mafic precursor phases conditioned the nucleation site and the crystallographic orientation of garnet because of topotaxial transformation reactions and homoepitaxial growth of garnet during the formation of high‐pressure, mafic garnet‐granulite after low‐pressure mafic protoliths.