Geophysical study of the San Juan Mountains batholith complex, southwestern Colorado

Drenth, Benjamin J.; Keller, G. Randy; Thompson, Ren A.

doi:10.1130/ges00723.1

Cited by 28 publications

(36 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All of these observations argue against the possibility that lamprophyres represent magmas that could have been parental to any volcanic rocks comprising the SJVF by closed system differentiation. This conclusion is supported by the fact that the lamprophyres are small volume intrusions that represent only a few 10 s of km 3 of magma; the SJVF contains 40,000+ km 3 of intermediate to felsic lavas and tuffs as well as an even larger underlying batholith (Lipman, 2007;Drenth et al, 2012).…”

Section: Closed System Processesmentioning

confidence: 54%

“…Geophysical constraints define a crustal batholith with an area of $10,000 km 2 underneath the San Juan Mountains (Drenth et al, 2012). Estimates from Lipman (2007) and Drenth et al (2012) constrain mafic to intermediate rock volumes (both batholith and exposed volcanics) in the San Juan Volcanic Field to $100,000-150,000 km 3 . An additional $16,000 km 3 of silicic ignimbrites are also exposed in the SJVF.…”

Section: Crustal Anatexismentioning

confidence: 99%

“…1). The SJVF is likely underlain by a voluminous ($100,000 km 3 ) granitic batholith, which is inferred to encompass up to half of the crustal column of southwestern Colorado (Plouff and Pakiser, 1972;Drenth et al, 2012). Volcanism within the San Juan region initiated at $35 Ma and swept from NE to SW over the following 10 million years.…”

Section: Introductionmentioning

confidence: 98%

“…After a brief respite Table 1 for GPS coordinates and sample descriptions). Adapted from Plouff and Pakiser (1972), Lipman (2007), and Drenth et al (2012).…”

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations

Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas

Lake

Farmer

2015

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Section: Closed System Processesmentioning

confidence: 54%

Section: Crustal Anatexismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

“…After a brief respite Table 1 for GPS coordinates and sample descriptions). Adapted from Plouff and Pakiser (1972), Lipman (2007), and Drenth et al (2012).…”

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas

Lake

Farmer

2015

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

“…Despite its size and importance, the existing geological studies (Gardeweg and Ramírez, 1987;Lindsay et al, 2001a, b) have several discrepancies regarding caldera limits, intra caldera ignimbrite thicknesses, collapse geometries and erupted volumes. We use gravimetry because it has been successfully used in caldera studies elsewhere to measure the subsurface caldera structure and deposit thickness -potentially resolving the discrepancies in previous interpretations (e.g., Rymer and Brown, 1986;Carle, 1988;Davy and Caldwell, 1998;Masturyono et al, 2001;Smith et al, 2006;DeNosaquo et al, 2009;Seebeck et al, 2009;Drenth et al, 2012). Based on both a gravity model and the reinterpretation of the ignimbrite stratigraphy, we suggest that the collapse geometry is significantly different than previously proposed, and that La Pacana caldera is made up of at least two nested calderas of different ages.…”

Section: Introductionmentioning

confidence: 99%

Nuevos antecedentes sobre la estructura interna de la caldera La Pacana mediante un estudio gravimétrico (Andes centrales, Chile).

Delgado

Pavez

2015

Andgeo

View full text Add to dashboard Cite

ABSTRACT. La Pacana (central Andes, Northern Chile) is one of the largest resurgent calderas in the world, formed 4 Ma ago during an eruption with a VEI of 8.7. We undertake a gravimetric study to contribute new insights into the inner structure and evolution of this caldera. The La Pacana Bouguer residual anomaly is asymmetric and has an average amplitude of -12 to -14 mGal, which we interpret as being produced by the low-density intracaldera ignimbrite infill. A reinterpretation of the caldera stratigraphy plus the available geochronology suggests that the current shape of La Pacana was produced by the collapse of two nested calderas, roughly limited by the axis where the resurgent dome changes its orientation, with the oldest eruption in the southern part of La Pacana. The gravity data suggests that these southern and northern nested structures would have collapsed with downsag and trap-door geometries respectively, evidence of asymmetric subsidence. Intra caldera ignimbrite thicknesses were calculated with 2.5D forward models and show that the ignimbrite infill in its southern and northern parts reach ∼0.6-1.1 km and ∼2.5-3 km respectively. Using Gauss's theorem, we calculate the volume of the intra caldera ignimbrite infill is ∼3,400-3,500 km 3 , in agreement with previous estimates and with models that show that the larger the caldera diameter, the larger the erupted volume.Keywords: La Pacana caldera, Volcanology, Gravimetry, Caldera collapse.RESUMEN. Nuevos antecedentes sobre la estructura interna de la caldera La Pacana mediante un estudio gravimétrico (Andes centrales, Chile). La Pacana (Andes centrales, norte de Chile) es una de las calderas resurgentes más grandes del mundo, formada 4 Ma atrás en una erupción con un VEI de 8,7. Hemos realizado un estudio gravimétrico de la caldera para contribuir con nuevos antecedentes sobre su estructura interna y evolución. La anomalía residual de Bouguer de La Pacana es asimétrica y tiene una amplitud promedio de entre -12 a -14 mGal, la que se interpreta que es producida por el relleno de baja densidad de ignimbritas intracaldera. Una reinterpretación de la estratigrafía de la caldera junto con la geocronología disponible sugiere que la forma actual de La Pacana fue producida por el colapso de dos calderas anidadas, cuyo límite aproximado sería el eje donde el domo resurgente cambia su orientación, y con la erupción más antigua en la parte sur de La Pacana. Los datos gravimétricos sugieren que estas estructuras anidadas sur y norte habrían colapsado con geometrías de tipo downsag y trap-door respectivamente, evidencias de subsidencia asimétrica. Los espesores de las ignimbritas intracaldera fueron calculados con modelos directos en 2.5D los cuales muestran que el relleno en sus partes sur y norte alcanza a los ∼0,6-1,1 km y ∼2,5-3 km respectivamente. Mediante el teorema de Gauss, calculamos que el volumen de las ignimbritas intracaldera llega a los ∼3.400-3.500 km 3 , de acuerdo con estimaciones previas y con modelos que muestran que mientras más grande es el di...

show abstract

Seismicity of the rocky mountains and Rio Grande Rift from the EarthScope Transportable Array and CREST temporary seismic networks, 2008–2010

2017

View full text Add to dashboard Cite

We developed a catalog of small magnitude (ML −0.1 to 4.7) seismicity across Colorado and New Mexico from the EarthScope USArray Transportable Array and CREST (Colorado Rocky Mountains Experiment and Seismic Transects) seismic networks from 2008 to 2010 to characterize active deformation in the Rio Grande Rift. We recorded over 900 earthquakes in the Rio Grande Rift region, not including induced earthquakes and mine blasts, and find that the rift is actively deforming both broadly and in distinct regions. Seismic events that are likely induced, mostly in the Raton Basin, make up 66% of the catalog (1837 earthquakes). Neogene faults in the northern rift in north central Colorado are seismically active in the North Park Basin and northwestern Colorado. The central rift from the San Luis Basin (southern Colorado) to south of the Socorro Magma Body is the most seismically active rift region, and seismicity delineates the deformation in the Colorado Plateau transition zone, which is spatially correlated with volcanic vents, dikes, and faults within the western Jemez Lineament. The eastern Jemez Lineament is nearly aseismic and surrounded by a halo of seismicity culminating in boundaries defined by recent moderate (Mw 3.9 and Mw 3.3) earthquakes. The southern rift is characterized by diffuse seismicity in Texas and Mexico. This study provides an updated seismic catalog built with uniformity in seismometer coverage and low epicentral uncertainties (~2 km) that allows for regional evaluation of seismicity. During this time period, clusters of seismicity and moderate magnitude earthquakes characterize deformation in a low‐strain rate extensional environment.

show abstract

Geophysical study of the San Juan Mountains batholith complex, southwestern Colorado

Cited by 28 publications

References 48 publications

Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas

Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas

Nuevos antecedentes sobre la estructura interna de la caldera La Pacana mediante un estudio gravimétrico (Andes centrales, Chile).

Seismicity of the rocky mountains and Rio Grande Rift from the EarthScope Transportable Array and CREST temporary seismic networks, 2008–2010

Contact Info

Product

Resources

About