Latir Volcanic Field

The Latir Volcanic Field is located in the Sangre de Cristo Mountains, northern New Mexico, with rocks and erosional remnants of the field covering an area of ~1200 km2. The late-Oligocene to early-Miocene field consists of volcanic and cogenetic plutonic rocks, with the latter exposed over an area of 20 x 35 km. It forms part of a composite mid-Tertiary volcanic field and being the most compositionally diverse magmatic centre active during the beginning of rifting in the northern Rio Grande rift. A major eruptive centre of the field is the Questa Caldera, ~15 km in diameter. The rocks are divided into four distinct groups emplaced in chronological order as follows: precaldera metaluminous basaltic-andesite to rhyolite lavas, ash flow tuffs and hypabyssal intrusions; alkalic dacite, comendite, peralkaline rhyolite flows, and a regional ash-flow tuff named the Amalia Tuff; post caldera peralkaline and metaluminous granite to granodiorite plutons; and alkali dacite to rhyolite and metaluminous to rhyolite lavas. Phenocryst phases within peralkaline lithologies include arfvedsonite, aegirine, tetrasilicic mica, with the early-erupted Amalia Tuff notably bearing rare accessory allanite. Associated with late calc-alkaline granitic ring intrusions along the southern margin of the Questa Caldera is major molybdenum mineralisation. Geochemical data including whole rock major and trace element and mineral chemical can be found in Johnson & Lipman (1988), with further whole rock data, detailed rock and locality descriptions, and stratigraphy found in Lipman (1983).