Elemental abundances of C, O, Na, Mg, Al, and Si for our sample stars. The black and green dashed lines represent the model predictions with solar metallicity and at an age of 4.0 and 5.0 Gyr, respectively (Dotter et al. 2017). The red dotted line represents the model predictions by O. Richard (priv. comm.). Open triangles and rectangles represent the elemental abundances for the subgiant and turn-off stars, respectively. The solar twin Y1194 is shown as an open circle.