Thermal and mass implications of magmatic evolution in the Lassen volcanic region, California, and minimum constraints on basalt influx to the lower crust

Citations Over TimeTop 19% of 1996 papers

Abstract

We have analyzed the heat and mass demands of a petrologic model of basalt‐driven magmatic evolution in which variously fractionated mafic magmas mix with silicic partial melts of the lower crust. We have formulated steady state heat budgets for two volcanically distinct areas in the Lassen region: the large, late Quaternary, intermediate to silicic Lassen volcanic center and the nearby, coeval, less evolved Caribou volcanic field. At Caribou volcanic field, heat provided by cooling and fractional crystallization of 52 km 3 of basalt is more than sufficient to produce 10 km of rhyolitic melt by partial melting of lower crust. Net heat added by basalt intrusion at Caribou volcanic field is equivalent to an increase in lower crustal heat flow of ∼7 mW m −2 , indicating that the field is not a major crustal thermal anomaly. Addition of cumulates from fractionation is offset by removal of erupted partial melts. A minimum basalt influx of 0.3 km 3 (km 2 Ma) −1 is needed to supply Caribou volcanic field. Our methodology does not fully account for an influx of basalt that remains in the crust as derivative intrusives. On the basis of comparison to deep heat flow, the input of basalt could be ∼3 to 7 times the amount we calculate. At Lassen volcanic center, at least 203 km 3 of mantle‐derived basalt is needed to produce 141 km 3 of partial melt and drive the volcanic system. Partial melting mobilizes lower crustal material, augmenting the magmatic volume available for eruption at Lassen volcanic center; thus the erupted volume of 215 km 3 exceeds the calculated basalt input of 203 km 3 . The minimum basalt input of 1.6 km 3 (km 2 Ma) −1 is >5 times the minimum influx to the Caribou volcanic field. Basalt influx high enough to sustain considerable partial melting, coupled with locally high extension rate, is a crucial factor in development of Lassen volcanic center; in contrast, Caribou volcanic field has failed to develop into a large silicic center primarily because basalt supply there has been insufficient.

Related Papers

• → Petrogenetic evolution of the felsic and mafic volcanic suite in the Siang window of Eastern Himalaya, Northeast India(2012)41 cited
• → Origin of K-feldspar megacrysts in rhyolites from the Emeishan large igneous province, southwest China(2017)21 cited
• → Geology, geochemistry and petrogenesis of Middle Tertiary volcanic rocks of the Queen Charlotte Islands, British Columbia (Canada)(1993)16 cited
• Geochemistry and petrogenesis of Eocene volcanic-intrusive rocks in Liaohe basin, northeastern China(2004)
• Lithofacies and reservoir characteristics of Late Carboniferous-Permian volcanic rocks in Niudong block, Santanghu Basin(2009)