Alluvial placer gold deposits that accumulate in streams across the globe are essentially allochthonous sedimentary deposits that are transported from their source to their location of deposition. The purpose of this study was to find placer gold deposits in alluvial sediments along the Indus River in the NW Himalaya of Pakistan. The investigated region was divided into five clusters based on river morphology. The research focused on mineralogical distribution, sediment source, gold transport distance, elemental composition, and gold concentration in river sediments. Throughout, during the deposition at point and channel bars, the mixed source of alluvial sediments was revealed by its mineralogical composition. However, the SEM analysis demonstrated that the gold grains had a high flatness index, indicating that they had been transported a significant distance. The elemental composition of several samples revealed a significant concentration of silicon dioxide, iron oxide, and alumina oxide transported from the Himalaya. The study of the trace elements indicated gold and related base metals with granitic provenance were transported from an acidic/granitic source. Based on gold concentration, it is demonstrated that the left riverbank (clusters C1, C2, and C3) has a higher concentration of gold deposits and higher potential for economic gold exploration than the right bank (clusters C4 and C5) due to the lower velocity of running water in the study area. The findings revealed that the studied area has good potential for commercial exploration of gold resources, and the workflow can be adopted in any region with a similar geological setting and morphology.
This study focused on analyzing the petroleum system of the Bannu Basin, which is the foreland basin of the Himalayan fold and thrust belts in Pakistan. The objectives of this study were achieved by dividing the study area into three zones, namely, the Southwestern zone, Southeastern zone, and Northeastern zone. The regional 2D seismic lines and well log data, including the bore hole temperature (BHT) and petrophysical and geochemical data, were integrated. The seismic interpretations and geohistory plots indicate higher levels of sedimentation and abrupt sedimentation from the Miocene until the Recent era due to the initiation of Himalayan orogeny. The thermal modeling indicates that potential source rocks are present in the basin, whereas the local faults in the Southwestern and Southeastern zones act as potential traps for the preservation of hydrocarbons. It is assumed that the Tredian Formation and Lumshiwal Formation are the potential reservoir rocks in the Southwestern zone, whereas the Warcha Formation and Tredian Formation are the economic reservoirs in the Southeastern zone. However, in the Northeastern zone, no major accumulation is present. The significant sedimentation of post-Miocene formations was the major event for the generation of hydrocarbons and a critical moment for the accumulation of hydrocarbons in the study area.
15 May 2021 in Journal of Petroleum Exploration and Production Technology
This paper presents the facies and depositional environment of the early Miocene Dam Formation, Eastern Arabian platform, Saudi Arabia. Deposition of Dam Formation (Fm.) was considered as a restricted shallow marine deposition. Few studies suggest the role of sea-level change in its deposition but were without decisive substantiation. Here, we describe the facies and high-resolution model of Dam Fm. under varying depositional conditions. The depositional conditions were subjected to changing relative sea level and tectonics. High-resolution outcrop photographs, sedimentological logs, and thin sections present that the mixed carbonate–siliciclastic sequence was affected by a regional tectonics. The lower part of Dam Fm. presents the development of carbonate ramp conditions that are represented by limestones and marl. The depositional conditions fluctuated with the fall of sea level, and uplift in the region pushed the siliciclastic down-dip and covered the whole platform. The subsequent rise in sea level was not as pronounced and thus allowed the deposition of microbial laminites and stromatolitic facies. The southeast outcrops, down-dip, are more carbonate prone as compared to the northwest outcrop, which allowed the deposition of siliciclastic-prone sedimentation up-dip. All facies, architecture, heterogeneity, and deposition were controlled by tectonic events including uplift, subsidence, tilting, and syn-sedimentary faulting, consequently affecting relative sea level. The resulting conceptual outcrop model would help to improve our understanding of mixed carbonate–siliciclastic systems and serve as an analogue for other stratigraphic units in the Arabian plate and region. Our results show that Dam Fm. can be a good target for exploration in the Northern Arabian Gulf.
Within the last three decades, twelve major earthquakes (Mw > 6.0) have jolted Pakistan and contributed to a heavy death toll and an economic loss of billions of dollars, which is immense for any underdeveloped country. Despite the generalized description of seismic hazards in various regions of Pakistan, densely populated cities still require a detailed and integrated vulnerability analysis to overcome the impact of a significant earthquake. This study aims to integrate seismic hazard assessment schemes to understand the vulnerability of Attock city against an earthquake. It initially evaluates the threat from an earthquake due to tectonic activity in the region, splits the region (about 200 km radius) into six seismic zones and uses area source parameters. The ground motion prediction equations compatible with the study area’s seismotectonic environment are also used in this study. Peak horizontal ground acceleration (PGA) and 5% damped spectral acceleration are critical features of ground motions. The site classification is carried within Attock city, indicating the presence of SB (foundation condition with Vs30 = 760 m/s), SC (foundation condition with Vs30 = 400 m/s) and SD (foundation condition with Vs30 = 300 m/s). The peak ground accelerations for a return period of 475 years at the SB, SC and SD sites are estimated as 0.23 g, 0.28 g and 0.30 g, respectively. Uniform hazard spectra are obtained for each site classification at three return periods (475, 975 and 2475 years). Another possible threat can be the local site conditions of the study area, as Attock city exists on the unlithified sediments of upper Pleistocene to Recent alluvial deposits. That is why microtremor recordings are conducted at 20 sites within Attock city to understand the fundamental frequency (f0), horizontal to vertical spectral amplitude (A0) and Kg parameter, a seismic vulnerability index. The values of f0 are found between 0.6 and 9 Hz and A0 is observed between 2.1 and 5 Hz, whereas the Kg is estimated between 0.24 and 20 Hz. Despite evidence of the seismic vulnerability of Attock city, the current building designs and infrastructure development are not synchronized with the uniform hazard response spectra and the soil amplification, thus enhancing the exposure of the study area to disaster during a major earthquake. This study will be instrumental in pre-disaster mitigation strategies for urban planners and policymakers.