Lithium depletion and enrichment in the cosmos is not yet well understood .
To help tighten constraints on stellar and Galactic evolution models , we present the largest high-resolution analysis of Li abundances A ( Li ) to date , with results for over 100 000 GALAH field stars spanning effective temperatures 5900 \mathrm { K } \lesssim T _ { \mathrm { eff } } \lesssim 7000 \mathrm { K } and metallicities -3 \lesssim \mathrm { \left [ Fe / H \right ] } \lesssim + 0.5 .
We separated these stars into two groups , on the warm and cool side of the so-called Li-dip , a localised region of the Kiel diagram wherein lithium is severely depleted .
We discovered that stars in these two groups show similar trends in the A ( Li ) - \mathrm { \left [ Fe / H \right ] } plane , but with a roughly constant offset in A ( Li ) of 0.4 \mathrm { dex } , the warm group having higher Li abundances .
At [ Fe / H ] \gtrsim - 0.5 , a significant increasing in Li abundance with increasing metallicity is evident in both groups , signalling the onset of significant Galactic production .
At lower metallicity , stars in the cool group sit on the Spite plateau , showing a reduced lithium of around 0.4 \mathrm { dex } relative to the primordial value predicted from Big Bang nucleosynthesis ( BBN ) .
However , stars in the warm group between \mathrm { \left [ Fe / H \right ] } = -1.0 and -0.5 , form an elevated plateau that is largely consistent with the BBN prediction .
This may indicate that these stars in fact preserve the primordial Li produced in the early Universe .