Temporal and geochemical trends of lavas in White Rock Canyon and the Pajarito Plateau, Jemez volcanic field
Giday WoldeGabriel, A. William Laughlin, David P. Dethier, and Matthew. Heizler
40Ar/39Ar dates and geochemical analyses provide insights into the geochronology and petrologic evolution of Miocene-Pliocene volcanism in the vicinity of White Rock Canyon and the adjacent Pajarito Plateau. Lava flows and some dikes were sampled from several stratigraphic sections in this area. 40Ar/39Ar results indicate 3 distinct pulses of volcanic activities at 9.3, 2.8 and 2.6-2.3 Ma. A single 9.3 Ma mugearitic lava flow occurs only locally, whereas the Pliocene volcanism is voluminous, widespread, and geochemically diverse. The earlier (2.8- 2.4 Ma) Pliocene lavas are predominantly evolved compositions (hawaiite, mugearite, benmorite, and dacite), whereas the latest (2.5-2.3 Ma) and stratigraphically uppermost flows are entirely tholeiitic basalts. The 9.3 Ma mugearite lava was erupted coevally with intense late Miocene (10-7 Ma) magmatic and tectonic activities in the Jemez volcanic field. The Pliocene (2.8-2.3 Ma) rift-bound volcanism appears to be contemporaneous with initiation of movement along the Pajarito fault zone. Despite temporal similarities and geographic proximity, the geochemical diversity of the White Rock Canyon volcanic rocks reflects different magmatic sources modified by differentiation and crustal contamination.
- WoldeGabriel, Giday; Laughlin, A. William; Dethier, David P.; Heizler, Matthew., 1996, Temporal and geochemical trends of lavas in White Rock Canyon and the Pajarito Plateau, Jemez volcanic field, in: The Jemez Mountains Region, Goff, Fraser; Kues, Barry S.; Rogers, Margaret Ann; McFadden, Les D.; Gardner, Jamie N., New Mexico Geological Society, Guidebook, 47th Field Conference, pp. 251-262.