Petrologic evolution of the San Juan volcanic field, southwestern Colorado: Pb and Sr isotope evidence

Lipman, Peter W.; Doe, Bruce R.; Hedge, Carl E.; Steven, Thomas A.

doi:10.1130/0016-7606(1978)89<59:peotsj>2.0.co;2

Cited by 203 publications

(83 citation statements)

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“…Observations in various intraplate and arc settings show that crustal magmatic systems evolve through the contribution of two end-member processes: 1) residual mantle-derived melt from crystallization of intruded magma and 2) crustal melt generated by partial melting of the crust (e.g., Deering et al, 2008;DePaolo, 1981b;DePaolo et al, 1992;Hildreth et al, 1991;Lipman et al, 1978). Our results suggest a combination of these two processes, although hydrous intrusions interacting throughout the crustal column tend to heavily favor residence of mantlederived melts over crustal melting.…”

Section: How Do Extensional Processes Affect Melt Location and Residementioning

confidence: 69%

Melt evolution and residence in extending crust: Thermal modeling of the crust and crustal magmas

Karakaş

Dufek

2015

Earth and Planetary Science Letters

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Available online xxxx Editor: T. Elliott Keywords: thermal model tectonic extension crustal melting fractionation crystal mush magma longevityTectonic extension and magmatism often act in concert to modify the thermal, mechanical, and chemical structure of the crust. Quantifying the effects of extension and magma flux on melting relationships in the crust is fundamental to determining the rate of crustal melting versus fractionation, magma residence time, and the growth of continental crust in rift environments. In order to understand the coupled control of tectonic extension and magma emplacement on crustal thermal evolution, we develop a numerical model that accounts for extension and thermal-petrographic processes in diverse extensional settings. We show that magma flux exerts the primary control on melt generation and tectonic extension amplifies the volume of melt residing in the crustal column. Diking into an extending crust produces hybrid magmas composed of 1) residual melt remaining after partial crystallization of basalt (mantle-derived melt) and 2) melt from partial melting of the crust (crustal melt). In an extending crust, mantle-derived melts are more prevalent than crustal melts across a range of magma fluxes, tectonic extension rates, and magmatic water contents. In most of the conditions, crustal temperatures do not reach their solidus temperatures to initiate partial melting of these igneous lithologies. Energy balance calculations show that the total enthalpy transported by dikes is primarily used for increasing the sensible heat of the cold surrounding crust with little energy contributing to latent heat of melting the crust (maximum crustal melting efficiency is 6%). In the lower crust, an extensive mush region develops for most of the conditions. Upper crustal crystalline mush is produced by continuous emplacement of magma with geologically reasonable flux and extension rates on timescales of 10 6 yr. Addition of tectonic effects and non-linear melt fraction relationships demonstrates that the magma flux required to sustain partially molten regions in the upper crust is within the range of estimates of magmatic flux in many rifting regions (∼10 −4 to 10 −3 km 3 /yr) and at least an order of magnitude lower than previous modeling estimates. Our results demonstrate the importance of tectonics in augmenting melt production, composition, and crustal evolution in active magmatic systems.

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Section: How Do Extensional Processes Affect Melt Location and Residementioning

confidence: 69%

Melt evolution and residence in extending crust: Thermal modeling of the crust and crustal magmas

Karakaş

Dufek

2015

Earth and Planetary Science Letters

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“…Previous researchers identified a mafic lower crust component in SJVF rocks (Lipman et al, 1978); could anatexis of mafic lower crust alone provide the mass required to produce the SJVF volcanic rocks and the inferred underlying batholith? To test the possibility we can take advantage of the covariation observed between the Nd isotopic composition and the bulk composition of Precambrian crust in Colorado (Farmer, 1992).…”

Section: Crustal Anatexismentioning

confidence: 99%

“…6B, C, and E). the injection of high e Nd mantle-derived magmas into the lower crust (Lipman et al, 1978;Riciputi and Johnson, 1990;Riciputi et al, 1995). This influx of basaltic magmas produced a MASH (Hildreth and Moorbath, 1988;Dufek and Bergantz, 2005;Annen et al, 2006), or "hot-zone", that was ultimately responsible for the generation of the magmas parental to the volcanic rocks and igneous intrusions of the SJVF.…”

Section: Basaltic-andesitic Intrusion Isotope Geochemistrymentioning

confidence: 99%

“…Previous studies of the SJVF (Lipman et al, 1978;Riciputi and Johnson, 1990;Perry et al, 1993;Riciputi et al, 1995) inferred that sustained injection of mantlederived magmas constructed a large lower crustal melting, assimilation, storage, and hybridization zone (MASH; e.g. Hildreth and Moorbath, 1988;Dufek and Bergantz, 2005;Annen et al, 2006) which silicic caldera-forming magma chambers tapped.…”

Section: Introductionmentioning

confidence: 99%

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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

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“…First, Lipman et al (1978) and Lipman (2007) have documented the temporal evolution of volcanic rocks in the San Juan Mountains (CO), showing that silicic magmatism only developed after intermediate composition lavas had accumulated over millions of years. The implication of this observation is that magmatic systems evolve with time to produce silicic rocks-they are not silicic initially.…”

Section: Hypothesis For Granitoid Origin By Thermal Migration Zone Rementioning

confidence: 99%

Hypothesis for the origin of convergent margin granitoids and Earth’s continental crust by thermal migration zone refining

Lundstrom

2009

Geochimica et Cosmochimica Acta

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Petrologic evolution of the San Juan volcanic field, southwestern Colorado: Pb and Sr isotope evidence

Cited by 203 publications

References 0 publications

Melt evolution and residence in extending crust: Thermal modeling of the crust and crustal magmas

Melt evolution and residence in extending crust: Thermal modeling of the crust and crustal magmas

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

Hypothesis for the origin of convergent margin granitoids and Earth’s continental crust by thermal migration zone refining

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