Lithostratigraphic contact – a significant site for hydrogeological investigation in crystalline fractured-rock terrains
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- 作者：Tapas Acharya ; Rajesh Prasad
- 关键词：Fractured rocks ; lithostratigraphic contact ; fracture frequency ; hydrogeology ; metamorphic rocks.
- 刊名：Journal of Earth System Science
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：126
- 期：1
- 全文大小：
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth Sciences, general; Space Sciences (including Extraterrestrial Physics, Space Exploration and Astronautics);
- 出版者：Springer India
- ISSN：0973-774X
- 卷排序：126
文摘
Estimating the hydrogeologic control of fractured aquifers in hard crystalline and metamorphosed rocks is challenging due to complexity in the development of secondary porosity. The present study in the Precambrian metamorphic terrain in and around the Balarampur of Purulia district, West Bengal, India, aims to estimate the hydrogeologic significance of lithostratigraphic contacts using fracture characteristics obtained from surface bedrock exposures supported by hydrological data from the existing dugwells. This study involves the domain-wise analysis of the frequencies of fractures that control the fracture-porosity. The domain-wise study reveals higher fracture-frequencies adjacent to the lithostratigraphic contacts. The concurrence of lithostratigraphic contacts with the occurrences of high-discharging wells and also with the deep weathered zone in low-lying areas is clearly established, thus assigning the lithostratigraphic contact as hydrogeologically significant. An increase in frequencies of the fractures within the ‘influence zone’ of the lithocontact, is clearly visible. Among those fractures, particularly, which make the angle greater than the ‘limiting angle’ with the lithocontact are characterised by increased frequencies. However, brittle rocks like quartz biotite granite gneisses, phyllite and epidiorite show high porosity of fracture, within the ‘influence zone’ of the lithostratigraphic contact. Enhanced deepening of the weathered-zone at lower topographic region may perhaps be a plausible explanation for this increased fracture-porosity at lithocontact to assign it as a hydrogeologically significant transmissive zone within fractured rocks.