Originally the second movement of Psathas' percussion work Muisca (PE184), Chia has now been arranged by the composer for solo piano. 

From the notes about the percussion version:

Sleepy yet mysterious, Chia sees the marimba and vibraphone enjoy some gentle melodic interplay, with the marimba then settling into a lightly swinging rhythmic bed in its rich lower register, allowing room for the vibraphone's statements in its resonant lower voice.