Chemical and Noble Gas Isotope Compositions of Formation Gases from a 3 km Deep Scientific Borehole in the Koyna Seismogenic Zone, Western India

Figure 5

Plot showing (a) ⁴He/²⁰Ne versus depth and (b) ⁴He/²⁰Ne versus ³He/⁴He, obtained from isotope measurements on gas samples collected during water flushing after core run 7/8. Error bars indicating uncertainty in the measurement are also shown. Depth of samples in “m” is indicated along with data points in (b). Inset shows mixing hyperbola between air and the continental crust and two different mantle end members (6 Ra for the lithospheric and 8 Ra for the asthenospheric mantle).

(a)

(b)