Reviewer Acknowledgements for Earth Science Research, Vol. 10, No. 2

Reviewer Acknowledgements for Earth Science Research, Vol. 10, No. 2, 2021.

Study of the Behavior of Gold and Accompanying Chemical Elements in Weathering Profile on a Quartz Vein in Mintom (South Cameroon, Central Africa)

The present study, which focuses on the behavior of gold and its accompanying chemical elements developed on an alteration profile, is carried out in a humid equatorial zone at Mintom in South Cameroon (Central Africa). The methodology used to achieve the results obtained focused on the description of the morphology of the outcrop, the petrography of the rock studied, the study of heavy minerals accompanying gold in the weathering materials on smear slides, mineralogical analysis of weathering materials by X-ray diffraction (XRD), scanning electron microscopy (SEM) analysis of gold and geochemical analyzes by ICP - AES and ICP - MS of weathering materials. The main results obtained from this methodology inform us that on the petrographic level the main rock studied is the gold-bearing quartz vein located in Zom, consisting mainly of quartz and opaque minerals. Morphologically, the weathering materials developed on this granite basement present an advanced ABC-type profile characterized by a significant thickness (4 to 6 m). The morphological and chemical characters of the gold particles have evolved from the mineralized zone to the surface. This development was marked by an increase in blunt, rounded grains. Morphoscopy and scanning electron microscopy of the gold particles have shown hollow, blunt to sub-blunt grains, non-evolved free particles, and evolved free particles, respectively. In most samples of weathered material gold is found in association with chemical elements such as Ag, Cr, Co, Cu, Ni, V and figure 10 show identical behavior between these chemical elements and gold, but particularly between silver and gold, which would testify to an identical origin. Au concentrations are very high in most samples of weathering material. Also, these samples of altered materials with a high proportion of gold (0.01 to 2.28 ppm) also present high concentrations of silver (Ag) which justifies that the occurrence or the gold deposit is associated with silver and can be exploited as a geochemical parameter to prospect for gold in the study area.

How Two Different Cenozoic Geologic and Glacial History Paradigms Explain the Southcentral Montana Musselshell-Yellowstone River Drainage Divide Origin, USA

The accepted Cenozoic geologic and glacial history paradigm (accepted paradigm) considers the southcentral Montana Musselshell-Yellowstone River drainage divide to have originated during Tertiary (or preglacial) time while a new and different Cenozoic geologic and glacial history paradigm (new paradigm) describes how headward erosion of a northeast-oriented Musselshell River valley segment captured huge southeast-oriented meltwater floods to create the drainage divide late during a continental ice sheet’s melt history. Northwest to southeast oriented divide crossings (low points observed on detailed topographic maps where water once flowed across the drainage divide), southeast-oriented Yellowstone and Musselshell River segments immediately upstream from northeast-oriented Yellowstone and Musselshell River segments, and southeast- and northwest-oriented tributaries to northeast-oriented Yellowstone and Musselshell River segments indicate a major southeast-oriented drainage system predated the northeast-oriented Yellowstone and Musselshell River segments. Closeness of the divide crossings, divide crossing floor elevations, large escarpment-surrounded erosional amphitheater-shaped basins, and unusual flat-floored internally drained basin areas (straddling the drainage divide), all suggest the previous southeast-oriented drainage system moved large quantities of water which deeply eroded the region. In the mid-20th century geomorphologists working from the accepted paradigm perspective determined trying to explain such erosional landform evidence from the accepted paradigm perspective was a nonproductive research activity and now rarely investigate erosional landform origins. On the other hand, the new paradigm appears to explain most, if not all observed erosional landform features, although the two paradigms lead to significantly different regional Cenozoic geologic and glacial histories that cannot be easily compared.  

Reservoir Characteristics of Buried-hill Draping Zone in L Oilfield, Offshore China

The reservoir in different parts of buried-hill draping zone is often quite different, so it is of great significance to clarify the reservoir characteristics for exploration and development. Based on core, well logging, seismic data and production data, reservoir characteristics of oil layer Ⅱ in the lower second member of Dongying Formation of L oilfield, Bohai Bay Basin, offshore eastern China are systematically studied. Analyses of seismic facies, well-seismic combination, paleogeomorphology, and sedimentary characteristics are carried out. Sediment source supply, lake level and buried hill basement geomorphology all contribute to reservoir quality. The research suggests that the different parts of buried-hill draping zone can be divided into four types. Reservoir thickness and physical properties vary. The area where the provenance direction is consistent with the ancient valley direction is a favorable location for the development of high-quality reservoirs. Under the guidance of the results, oilfield production practices in L oilfield offshore China are successful. Knowledge gained from study of L oilfield has application to the development of other similar fields.

Ionic Strength and Drag Reduction of Polymers in Straight Pipes – An Experimental Investigation

Previous work has tied the drag reduction properties of polymer solutions to type and concentration of salts, rather than its ionic strength, although it is a more extensive parameter to investigate the effects of salt contents on fluids behavior. The current study aims at investigating the relationship between ionic strength and drag reduction characteristics of polymer solutions when flowing in straight tubing. Nalco ASP-700 and ASP-820, two common anionic AMPS copolymers, are examined with various salts (2% KCl, 4% KCl, and synthetic seawater). Flow tests were conducted using a small-scale flow loop that includes a straight tubing with an outside diameter of 1.27 cm and a length of 4.57 m. It has been found that drag reduction performance of polymer solutions is well correlated with ionic strength, rather than salt type and/or concentration. With high ionic strength, lower drag reduction is noticed despite of the reduced salt concentration. Nevertheless, at higher Reynolds number, the effects of ionic strength minimizes. Both polymer solutions exhibit effective drag reduction characteristics and their behavior is greatly affected by polymer type, shear rate, and salt content. Correlations, with acceptable confidence level, between drag reduction ratio and solutions ionic strength are proposed. The correlations are strongly recommended to investigate the effects of salt types and/or concentrations, represented by its ionic strength on drag reduction behavior of polymer solutions in straight tubing.

Mapping of Flood Zones in Urban Areas through a Hydro-climatic Approach: the Case of the City of Abha

Flooding is a natural phenomenon of the hydrological cycle, but it has become an urban concern in many cities around the world. Due to human intervention on the functioning of hydrosystems through infrastructure, the channelling of watercourses, the redirection of the flow and the inevitable extension of the urban landscape, floods have become a growing urban hazard. Several cities are currently facing very frequent flash floods. These floods are of various types and several factors are at the origin of their manifestation, which leaves its understanding and prevention for local stakeholders a long-term process that requires a colossal amount of work among several multidisciplinary researchers. Without denying the scientific consensus on the role of climate change, currently floods are largely caused by the senseless and irresponsible behaviour of humans. Among the cities in Saudi Arabia facing the risk of flooding is the city of Abha located in the southwest of the country, the focus of this research. It is subject to recurrent and devastating floods caused by several factors. Controversial topography, dissected orography, aggressive rainfall, accelerated and unregulated urban growth, and irresponsible human intervention are all factors that aggravate this problem. The resolution of this problem, or at least the minimization of its consequences, requires a rigorous and carefully studied approach. The appropriate knowledge by local stakeholders must be reinforced by a methodological and cartographic assessment of this phenomenon in order to mitigate its consequences. The main objective of this work is to make cartographic and methodological contributions to acquire additional knowledge on the flood hazard in the city of Abha through a statistical processing of rainfall data for the period 1978-2018, a mapping of the factors intervening on the runoff and its various behaviors and finally a synthetic analysis.

Reviewer Acknowledgements for Earth Science Research, Vol. 10, No. 1

Reviewer Acknowledgements for Earth Science Research, Vol. 10, No. 1, 2021.

Alteration Mapping for Lead-Zinc-Barium Mineralization in Parts of the Southern Benue Trough, Nigeria, Using ASTER Multispectral Data

The lead-zinc-barium deposits of the southern Benue Trough, Nigeria belong to a suite of clastic dominated fracture filling hydrothermal vein deposits. The alteration types and spread are poorly known yet required to aid exploration. Band ratio composites (BRC), Principal Component Analysis (PCA), and Minimum Noise Fraction (MNF) were applied to a full scene Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery covering the study area. Spectral analysis of sulphide minerals known in the area led to the development of the (B1+B3)/2 ratio, which provided a highly effective sulphide discriminant. PCA and MNF bands with high eigenvectors in the absorption features of target minerals qualified as colour composite candidates for alteration mapping. This study demonstrated the effectiveness of combining the BRC, PCA and MNF techniques in the discrimination of ferric-ferrous/sulphide and silica alteration zones in the Southern Benue Trough.

Topographic Map Analysis of the North Platte River-South Platte River Drainage Divide Area, Western Larimer County, Colorado, USA Eric Clausen

The United States Supreme Court settled legal disputes concerning four different Larimer County (Colorado) locations where water is moved by gravity across the high elevation North Platte-South Platte River drainage divide, which begins as a triple drainage divide with the Colorado River at Thunder Mountain (on the east-west continental divide and near Colorado River headwaters) and proceeds in roughly a north and northeast direction across deep mountain passes and other low points (divide crossings) first as the Michigan River (in the North Platte watershed)-Cache la Poudre River (in the South Platte watershed) drainage divide and then as the Laramie River (in the North Platte watershed)-Cache la Poudre River drainage divide. The mountain passes and nearby valley and drainage route orientations and other unusual erosional features can be explained if enormous and prolonged volumes of south-oriented water moved along today’s north-oriented North Platte and Laramie River alignments into what must have been a rising mountain region to reach south-oriented Colorado River headwaters. Mountain uplift in time forced a flow reversal in the Laramie River valley while flow continued in a south direction along the North Platte River alignment only to be forced to flow around the Medicine Bow Mountains south end and then to flow northward in the Laramie River valley and later to be captured by headward erosion of the east-oriented Cache la Poudre River-Joe Wright Creek valley (aided by a steeper gradient and less resistant bedrock). Continued uplift next reversed flow on the North Platte River alignment to create drainage routes seen today. While explaining Larimer County North Platte-South Platte drainage divide area topographic map drainage system and erosional landform evidence this interpretation requires a completely different Cenozoic history than the geologic history geologists usually describe.

Common Ingredients and Orographic Rain Index (ORI) for Heavy Precipitation Associated with Tropical Cyclones Passing Over the Appalachian Mountains

Relative contributions of common ingredients to heavy orographic rainfall associated with the passage of Hurricanes Hugo (1989) and Isabel (2003) over the Appalachian Mountains are examined using a numerical weather prediction model. It is found that the key ingredients for producing local heavy orographic rainfall were: high precipitation efficiency, strong low-level flow, strong orographically forced upward motion associated with strong low-level flow over relatively gentle upslope, concave geometry providing local areas of convergence, high moist flow upstream, a relatively large convective system associated with both tropical cyclones (TCs), and relatively slower movement. In addition, neither conditional instability nor potential (convective) instability is found to play essential roles in producing strong upward motion leading to heavy orographic TC rain. A modified Orographic Rain Index (ORI) is proposed as a predictor for heavy orographic TC precipitation, which includes the upstream incoming horizontal wind speed normal to the local orography, the steepness of the mountain, the relative humidity, the TC moving speed, and the horizontal scale of the TC. It is found that the ORI estimated in regions of local maximum rainfall by using fine-resolution numerically simulated results correlate well with rainfall rates for both hurricanes, indicating that it may serve as a predictor for heavy orographic TC rainfall.