Facts and hypotheses regarding the Miocene–Holocene Jemez Lineament, New Mexico, Arizona and Colorado
— Fraser Goff and Shari A. Kelley


The Miocene to Holocene Jemez Lineament (JL) consists of 10 volcanic fields stretching northeast from San Carlos in Arizona to Raton–Clayton in New Mexico and Colorado. We have tabulated data on volcanic style, magma composition, number of volcanic vents, age range, eruptive areas, eruptive volumes, presence of xenoliths and enclaves, significant sites, and significant references for all volcanic fields. The width of each field, based on total extent of mapped volcanic rocks perpendicular to the trend of the lineament, is highly variable; thus, as pointed out by others, magma ascent and volcanism cannot be controlled by a single fault or structure. Volcanic landforms are highly variable from field to field. Spatial-temporal trends are complex, and there is no systematic age progression in either direction; thus, the JL is not a hot-spot trend. There is also no compositional progression along the JL, although intermediate to silicic volcanism and tholeiitic basalts are most common toward the center of the lineament and the cross-cutting Rio Grande rift (RGR). Estimated surface areas and eruptive volumes of each field are highly variable. The Jemez Mountains volcanic field that formed at the intersection of the JL and RGR has erupted three times more volcanic products than all other volcanic fields combined. Recent geophysical studies have highlighted the presence of low-velocity (Vs <4.2 km/s) upper mantle all along the JL and have mapped stark differences in 2008–2010 JL seismicity on either side of the RGR. The only geothermal system along the JL with electrical potential (200–300°C) circulates within the 1.25 Ma Valles caldera (now a National Preserve), but low-temperature geothermal systems occur elsewhere along the JL. Two CO2 gas fields are found at relatively shallow depths (≤1000 m) toward either end of the JL near the Springerville and Raton–Clayton volcanic fields. He- and C-isotopes indicate the gases are predominately derived from mantle sources. Extractable commodities have been perlite, pumice, sulfur and construction materials, and epithermal gold-silver was mined in the southeastern Jemez Mountains. The Grants uranium district underlies the Mount Taylor volcanic field, but a connection between remobilized (3 to 12 Ma) uranium deposition and magmatism has not yet been firmly established. Many researchers consider the older crustal structure beneath the JL to be a boundary between Proterozoic crustal provinces. Geophysical and geochemical observations support the idea that the Mesoproterozoic ancestry of this feature created fertile mantle lithosphere that has become part of the North American plate. Spacing between JL volcanic fields resembles volcano spacing found along many currently active subduction zones, although evidence for Paleoproterozoic arc-type volcanism is equivocal. Certainly, the alkaline affinity of volcanic rocks along much of the JL does not resemble the dominantly calc-alkaline magmatism of most subduction zones. Recent 40Ar/39Ar dating in the Raton–Clayton field indicates that the plate motion signal on time scales less than 1 Ma might constantly be present, but we currently do not have the spatial-temporal resolution to detect that pattern elsewhere along the JL.

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Recommended Citation:

  1. Goff, Fraser; Kelley, Shari A., 2021, Facts and hypotheses regarding the Miocene–Holocene Jemez Lineament, New Mexico, Arizona and Colorado, in: New Mexico Geological Society, 71st Annual Fall Field Conference, September 2021, Geology of Mount Taylor, Frey, Bonnie A.; Kelley, Shari A.; Zeigler, Kate E.; McLemore, Virginia T.; Goff, Fraser; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, pp. 101-116. https://doi.org/10.56577/FFC-71.101

[see guidebook]