AGE AND DISTRIBUTION OF VOLCANIC VENTS THROUGHOUT THE SNAKE RIVER PLAIN VOLCANIC PROVINCE, IDAHO

As part of our DOE-funded research effort on volcanism and geothermal energy in southern Idaho, we have created a database of basaltic vents and associated rhyolite domes across the Snake River Plain Volcanic Province (SRP) and surrounding regions in southern Idaho and eastern Oregon. The database contains over 1100 mafic vents and rhyolite domes, along with their ages and magnetic polarity. The vents are binned by age, with finer divisions in the Pleistocene/Holocene that reflect the higher age resolution available for Pleistocene lavas. Potential buried vents are interpreted from magnetic anomaly data.

Silicic eruptive centers form a time-transgressive pattern across the eastern SRP (ESRP) that reflects the path of North America over the Yellowstone-SRP Hotspot, from the ~ 12 Ma Bruneau-Jarbidge eruptive center in the central SRP to active volcanism at Yellowstone. Older (14-16 Ma) rhyolite eruptive centers formed across SW Idaho and SE Oregon. Basaltic volcanism exhibits time trends that are not strictly related to plate motion. The ESRP from about Twin Falls to Island Park is dominated by young tholeiitic basalts 75-400 ka in age that define an Axial Volcanic Zone (AVZ). Somewhat older basalts (400-780 ka) are exposed in areas where the younger volcanism is scarce, or in areas away from the AVZ. The youngest vents are concentrated along the Craters of the Moon-Great Rift trend. To the southwest, vents of the Bruneau-Jarbidge (BJ) center are Pliocene-lower Pleistocene, while the Owyhee Plateau is dominantly Miocene in age. Rhyolite domes occur both on the margins and within the AVZ with ages as young as 50 ka.

Surprisingly, the western SRP (WSRP), which initially formed in conjunction with the BJ center circa 10-12 Ma, is dominated by middle Pleistocene (0.78-2.58 Ma) vents of tholeiitic basalt. Additionally, it contains a number of younger (75-780 ka) high-K transitional basalts along the WSRP axis and farther north through the Idaho Batholith, where vents have been dated as young as 2 ka.

The distribution of vent ages show that mafic volcanism persisted long after passage of NA over the active plume tail. This is consistent with sublithospheric flow of plume-derived asthenosphere, controlled in part by lithospheric channels formed during interaction with the active plume tail (e.g., as proposed by Jean et al., 2014, EPSL).