Central Geological Survey, MOEA

About: Central Geological Survey, MOEA is a government organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Landslide & Fault (geology). The organization has 68 authors who have published 81 publications receiving 2037 citations. The organization is also known as: Jīngjì Bù Zhōngyāng Dìzhí Diàochá Suǒ.

Prediction of hydraulically transmissive fractures using geological and geophysical attributes: a case history from the mid Jhuoshuei River basin, Taiwan

Abstract: The feasibility of using geological and geophysical well-log and borehole-televiewer data for the identification of hydraulically transmissive fractures is evaluated. Twenty-nine boreholes were drilled to a depth of 100 m in the middle-stream basin of Jhuoshuei River, Taiwan. Four criteria that assist in indicating the potential presence of permeable zones are proposed, including: lower gamma-ray response compared with the average response, divergence of the short normal-resistivity log relative to that of the long one, longer sonic travel time, and the appearance of discernible openings detected with the televiewer. With these, the transmissivities at the predetermined depths were estimated and verified by an in-situ hydraulic test. The statistical results indicate that, particularly in the mountainous area where a complex folded structure with a succession of synclines and anticlines is shown, the interpretation of lithologic conditions is not necessary to identify the presence of a relatively higher-permeability zone. Comparatively, the estimates of porosity and fracture aperture are the necessary premises to the prediction of hydraulically transmissive fractures. A joint consideration of all four criteria is found, allowing a less biased evaluation of the fracture transmissivity.

Hydrothermal alteration of andesite in acid solutions: Experimental study in 0.05 M H2SO4 solution at 110 °C

Abstract: The experimental results indicate that the plagioclase and pyroxenes in the treated samples show micropits and microfractures. Small crystals readily suffered from alteration, as compared with large ones, and the susceptibility of the minerals to the acid solution is decreased in the order of plagioclase, augite, hypersthene and opaque minerals. Plagioclase, which is the most reactive mineral in the experiments, shows an increase of SiO2, but a decrease of Al2O3, CaO and Na2O as the experiments proceeded. The chemical change of the treated andesite, it indicates that the relative amounts of SiO2 ,T iO2, MgO,FeO, MnO and K2O increase, while those of Al2O3, CaO, Na2O and P2O5decrease with an increase of the experimental duration. The relative mobility of chemical elements listed in decreasing order is P, Ca, Al, Na, Si, K, Mg, Fe, Mn and Ti in terms of the Kv alue. It is no wonder that Ca, Al and Na are more mobile than others because these el- ements are readily released into solution from the more reactive plagioclase, while Mg, Fe etc. still stay in the less reactive pyroxenes and opaque minerals.