Petrophysical properties of the Deccan basalts exposed in the Western Ghats escarpment around Mahabaleshwar and Koyna, India
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- 作者：K.J. Prasanna Lakshmi ; kjplakshmi@ngri.res.in" class="auth_mail ; P. Senthil Kumar ; K. Vijayakumar ; S. Ravinder ; T. Seshunarayana ; Mrinal K. Sen
- 关键词：Deccan basalts ; Petrophysical stratigraphy ; Density ; P and S wave velocity ; Porosity ; Poisson&rsquo ; s ratio
- 刊名：Journal of Asian Earth Sciences
- 出版年：15 April, 2014
- 年：2014
- 卷：84
- 期：Complete
- 页码：176-187
- 全文大小：2862 K
文摘
We present petrophysical properties (density, P and S wave velocity, porosity and Poisson鈥檚 ratio) of the Deccan basalts from the Western Ghats escarpment around Mahabaleshwar and Koyna and characterize the Dhawar basement rocks around Goa. The petrophysical properties of basaltic lava flows show significant variation in the Bushe, Poladpur, Ambenali and Mahabaleshwar Formations that are widespread in the Deccan volcanic province. The Bushe Formation stands out distinctly from other formations because of its lower density, and P and S wave velocity. The porosity (vesicles and amygdales) plays a major role in controlling the variation of the petrophysical properties of the basalts. The Poisson鈥檚 ratio of the Deccan basalts is largely affected by the vesicular porosity, aspect ratio of the amygdales, and zeolite content. The Dharwar basement rocks (greywackes and granites) are found to be lower in density, P and S wave velocity, and Poisson鈥檚 ratio than the basaltic rocks. The variation of the petrophysical properties with elevation in the Western Ghats sections roughly follows the geochemical stratigraphy. High porosity of the Bushe and Mahabaleshwar Formations constitute a multi-layered aquifer system in the Deccan volcanic province. In the Koyna earthquake zone, these formations may provide an effective groundwater connectivity between the reservoir and earthquake focal areas. The new petrophysical data of the Deccan basalts and Dharwar basement rocks will help to refine the geophysical models of the southwestern Deccan basalt province.