Latir volcanic field

[2] The volcanic field has been deeply eroded, in many places to Proterozoic basement rock, and the underlying plutons are widely exposed.

[2][3] Erosional remnants of the Latir field are found on the west side of the Rio Grande rift in the Tusas Mountains.

The area was thrust eastward during the Laramide orogeny, then eroded to low relief, removing much of the sedimentary cover and depositing small amounts of Eocene to Oligocene sediments.

[2] The earliest volcanism began about 30 Ma and consisted mostly of intermediate composition magmas (andesite and dacite) with small amounts of higher-silica rhyolite erupted from numerous vents.

[2] The batholith broke through to the surface at 25 Ma and erupted some 500–1,000 cubic kilometres (120–240 cu mi) of peralkaline (alkali-rich) rhyolite ash flows[3] to form an outflow sheet of densely welded Amalia Tuff.

For example, fission track dating shows that the upper part of the batholith beneath the caldera had cooled to 100°C by a million years after emplacement and that uplift increased to the south.

It has been suggested[1] that this migration of volcanic activity heated and weakened the lithosphere along its path to produce focuses for later extensional deformation of the eastern Cordillera.

[5][8] However, the precaldera rocks are overwhelmingly derived from basaltic magmas produced in the upper mantle, rather than melted crust.

[8] The Amalia Tuff magma formed from a parent that was enriched in alkali metals and trace elements and had a large component of melted crust.

[9] The growth of the Latir volcanic field produced enormous quantities of volcaniclastic sediments (Abiquiu Formation).

The mineral zone is dominated by pyrite, alkali feldspar, fluorite, calcite, and quartz,[3] with the chief molybdenum ore being molybdenite.

Production began in the spring of 1919 and ore was concentrated at a converted gold mill on the Red River above the mine.