Deciphering a Quantitative Relationship Between Rifting and Crustal Melt Fraction: Insights From the Incipient Okavango Rift Zone

Abstract Rifting and magmatism are fundamental geological processes in the evolution of the lithosphere; however, quantitative investigations of their relationship are rare. The Okavango Rift Zone (ORZ) is in the early stages of rifting and magmatic activity and thus is an ideal locale to study this relationship. We examine the relationship using two primary crustal structure parameters: crustal thickness and average Vp/Vs ratio obtained from receiver functions. Our large Vp/Vs estimates indicate the existence of melts within the crust of the ORZ. Comparing our results with those of other continental rifts, we identify a quantitative relationship between rifting and crustal melt fraction. Additionally, the comparative analysis suggests that melts within a rift crust are introduced only when the stretching magnitude reaches that of the ORZ. We also propose a model suggesting that with the progression of rifting, melts would be introduced into the crust and increased gradually, potentially triggering rift‐related volcanism.