Boron concentration in different maar-diatreme volcanic environments.

The Pinacate Volcanic Field is located just near the northern end of the Gulf of California. Extensive alkaline basaltic lava flows (2000 km ) cut through by more than 400 vents, predominantly scoria cones. The maar vents erupted immediately after emplacement of pre-maar lava flows. Two huge phreatomagmatic vents are spectacular: Crater Elegante ( and Cerro Colorado. The formation of phreatomagmatic vents were largely controlled by the existence or nonexistence of alluvial siliciclastic sediments along former river valleys assigned as an ancestor of the Sonoyita River. 2