OF-01-01 Geologic Map of the Castle Rock Gulch Quadrangle, Chaffee and Park Counties, Colorado

Wallace, C.A.; Keller, John W.

doi:10.58783/cgs.of0101.qfnd4728

Cited by 1 publication

(2 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Quartz monzonite sills around Swan Mountain were previously dated with Rb‐Sr geochronology (biotite‐whole rock isochron; 45 Ma, no uncertainty provided; Simmons & Hedge, 1978), and more recently a sample collected east of Breckenridge yielded an 40 Ar/ 39 Ar biotite age of 45.27 ± 0.12/1.02 Ma (J. W. Keller et al., 2017). The sample we collected is from the northernmost exposure of the sill complex and is distinctly younger than previous 40 Ar/ 39 Ar ages (43.446 ± 0.023/0.053 Ma; Figure 3a), which suggests it crystallized after sills to the south cooled below Ar closure.…”

Section: Discussionmentioning

confidence: 99%

“…The ca. 48 to 45 Ma Swan Mountain complex (Bryant et al., 1981; J. W. Keller et al., 2017) is composed of monzonites and a younger quartz monzonite porphyry, and contains some of the largest sills that intruded in the region during this timeframe. The largest Laramide plutons in the CMB include the Twin Lakes batholith, which was episodically assembled between 60 to 57 Ma and 43 to 40 Ma (Feldman, 2010) and the 38.8 Ma Montezuma pluton (Rosera et al., 2021).…”

Section: Geological Settingmentioning

confidence: 99%

See 1 more Smart Citation

Using Stochastic Point Pattern Analysis to Track Regional Orientations of Magmatism During the Transition to Cenozoic Extension and Rio Grande Rifting, Southern Rocky Mountains

Rosera,

Gaynor,

Ulianov

et al. 2024

Tectonics

View full text Add to dashboard Cite

The southern Rocky Mountains in Colorado and northern New Mexico hosted intracontinental magmatism that developed during a tectonic transition from shortening (Laramide orogeny, ca. 75 to 40 Ma) through extension and rifting. We present a novel approach that uses stochastic weighted bootstrap simulations of a large set of new and historical geochronology data to better understand how regional anisotropies responsible for focusing magma emplacement evolved through time. This technique can detect subtle trends in directional distributions, including multi‐modal orientations, and can be filtered from regional to local scales. Our results indicate that magmatism followed first the northeast trend of the Colorado mineral belt between 75 and 40 Ma and deviated afterward. These deviations vary depending on the scale of the analysis. At the smallest scale we evaluated (<75 km), the orientation of magmatism from 45 to 30 Ma rotated counter‐clockwise before aligning with the north‐south trend of the modern Rio Grande rift. Larger, regional‐scale analyses indicate magma centers between 40 to 35 Ma and 25 to 20 Ma were dominantly oriented southwest‐northeast, whereas magmatism between 35 and 25 Ma had north‐south orientation. The large areal footprint of magmatism and shifting regional patterns suggest that ancient zones of weakness in the North American lithosphere accommodated magma flow at different moments in time, rather than controlled by a retreating interface of the Farallon and North American plates.

show abstract

Section: Discussionmentioning

confidence: 99%