Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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40Ar-39Ar Darting of Deccan Basalts


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1 Physical Research Laboratory, Ahmedabad 380 009, India
     

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The feasibility of dating igneous rocks by the 40Ar-39Ar method in India using the Apsara nuclear reactor at BARC, Bombay is reported, based on measurements on two tholeiitic basalts and one alkali basalt associated with the Deccan volcanism. The ages of the tholeiitic basalts are 71±4 Ma and 65±4 Ma, respectively and that of the alkali basalt is 682 Ma. Apart from the low neutron flux requiring long irradiation times, the neutron fluence within the sample irradiation volume is somewhat anisotropic. The latter needs to be minimised to achieve the higher precision the method is capable of.
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  • 40Ar-39Ar Darting of Deccan Basalts

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Authors

T. R. Venkatesan
Physical Research Laboratory, Ahmedabad 380 009, India
K. Pande
Physical Research Laboratory, Ahmedabad 380 009, India
K. Gopalan
Physical Research Laboratory, Ahmedabad 380 009, India

Abstract


The feasibility of dating igneous rocks by the 40Ar-39Ar method in India using the Apsara nuclear reactor at BARC, Bombay is reported, based on measurements on two tholeiitic basalts and one alkali basalt associated with the Deccan volcanism. The ages of the tholeiitic basalts are 71±4 Ma and 65±4 Ma, respectively and that of the alkali basalt is 682 Ma. Apart from the low neutron flux requiring long irradiation times, the neutron fluence within the sample irradiation volume is somewhat anisotropic. The latter needs to be minimised to achieve the higher precision the method is capable of.