Structural Mapping of the Bentong‐Raub Suture Zone Using PALSAR Remote Sensing Data,Peninsular Malaysia: Implications for Sediment‐hosted/Orogenic Gold Mineral Systems Exploration

The Bentong‐Raub Suture Zone (BRSZ) of Peninsular Malaysia is one of the major structural zones in Sundaland, Southeast Asia. It forms the boundary between the Gondwana‐derived Sibumasu terrane in the west and Sukhothai Arc in the east. The BRSZ is genetically related to the sediment‐hosted/orogenic gold deposits associated with the major lineaments in the Central Gold Belt of Peninsular Malaysia. In this investigation, the Phased Array type L‐band Synthetic Aperture Radar (PALSAR) satellite remote sensing data were used to map major geological structures in Peninsular Malaysia and provide detailed characterization of lineaments and curvilinear structures in the BRSZ, as well as their implication for sediment‐hosted/orogenic gold exploration in tropical environments. Major structural lineaments such as the Bentong‐Raub Suture Zone (BRSZ) and Lebir Fault Zone, ductile deformation related to crustal shortening, brittle disjunctive structures (faults and fractures) and collisional mountain range (Main Range granites) were detected and mapped at regional scale using PALSAR ScanSAR data. The major geological structure directions of the BRSZ were N–S, NNE–SSW, NE–SW and NW–SE, which derived from directional filtering analysis to PALSAR fine and polarimetric data. The pervasive array of N–S faults in the Central Gold Belt and surrounding terrain is mainly linked to the N–S trending of the Suture Zone. N–S striking lineaments are often cut by younger NE–SW and NW–SE‐trending lineaments. Gold mineralized trend lineaments are associated with the intersection of N–S, NE–SW, NNW–SSE and ESE–WNW faults and curvilinear features in shearing and alteration zones. Compressional tectonic structures such as the NW–SE trending thrust, ENE–WSW oriented faults in mylonite and phyllite, recumbent folds and asymmetric anticlines in argillite are high potential zones for gold prospecting in the Central Gold Belt. Three generations of folding events in Peninsular Malaysia have been recognized from remote sensing structural interpretation. Consequently, PALSAR satellite remote sensing data is a useful tool for mapping major geological structural features and detailed structural analysis of fault systems and deformation areas with high potential for sediment‐hosted/orogenic gold deposits and polymetallic vein‐type mineralization along margins of Precambrian blocks, especially for inaccessible regions in tropical environments.     

Assessing factors affecting drought,earthquake, and flood risk perception: empirical evidence from Bangladesh

Natural Hazards - Understanding household disaster risk perception is crucial to formulate and apply disaster risk reduction strategies. Using survey data from 300 households from three highly...     

Multivariate fire risk models using copula regression in Kalimantan,Indonesia

Natural Hazards - Forest fires have become a national issue yearly and elicited serious attention from the government and researchers in Indonesia. Copula-based joint distribution can construct a...     

A search for correlation between seismicity and radon anomaly in hot springs

Measurements of radon contents of the exholved gas emanating from several hot water springs along the Western Coast of India are reported here. Concentration of radon in gas phase of individual springs varied in general, directly with the surface temperature of the water emerging from the respective springs, and showed little variation with time. Radon measurements were carried out continuously for about two years at two hot springs located at Ganeshpuri and Sathivali in the coastal area of Northern Maharashtra. The distant tremors did not cause any variation in the radon content. There was no marked local seismic activity during the period of observations, and the levels of radon stayed essentially constant. The measurements were also carried out at a hot spring in Assam, for about 8 months. These also did not show any significant variation; this period too lacked any marked local seismicity.     

Determination of the rate and volume of leakage using the slopes of time-drawdown data

Quantification of leakage is very important in the selection and design of the remediation systems of leaky aquifers that receive contaminated leakage. This is an approach for the calculation of leakage using only two slopes of time-drawdown data. These slopes represent before and after the start of leakage, and are applied to four examples. Results generally agree with those determined by the Hantush approach. Comparison of the two approaches, however, shows that the Hantush approach quantifies leakage using three aquifer parameters (transmissivity, storativity, and leakage factor), the value of which depend on the pumping test method used; it assumes constant hydraulic head in the aquifer supplying leakage, which may not be valid under field conditions; and it ignores differences between the viscosities of the leakage water and the aquifer water, which influence the leakage rate. The proposed approach is free from all three limitations.     

Alkylbenzenes in mussels from South and South East Asian coasts as a molecular tool to assess sewage impact

Alkylbenzenes, molecular markers of sewage, were measured in 34 green mussels collected from India, Indonesia, Malaysia, Thailand, Cambodia, Vietnam, and the Philippines together with blue mussels collected from Tokyo Bay, Japan. Linear alkylbenzene (LAB) concentrations in South and South East Asian countries ranged from 10 to 1640 ng-∑LAB/g-dry tissue. In some populous cities, LAB concentrations were similar or higher than those found in northern Tokyo Bay which is heavily impacted by sewage effluents. I/E ratios (a ratio of internal to external isomers of LABs) in the South and South East Asian countries (1–3) were much lower than those in Tokyo Bay (3–8), indicating sewage discharged in the coastal zone is poorly treated (e.g., raw sewage and/or primary effluents). Alkylbenzenes with branched alkyl chains, tetrapropylene-based alkylbenzenes, were also detected in mussels from Indonesia and Philippines. This “tell-tale” sign indicates that poorly degradable detergents are still in use in this area, although they have long been phased-out in many industrialized countries.