Petrogenesis and volcanology of anorogenic rhyolites: a special issue dedicated to Bill Bonnichsen
- PDF / 68,429 Bytes
- 3 Pages / 595.276 x 790.866 pts Page_size
- 53 Downloads / 161 Views
EDITORIAL
Petrogenesis and volcanology of anorogenic rhyolites: a special issue dedicated to Bill Bonnichsen Michael McCurry & Eric H. Christiansen & William P. Leeman
Received: 15 May 2006 / Accepted: 8 March 2007 / Published online: 20 June 2007 # Springer-Verlag 2007
The occurrence of large volume, high-temperature silicic volcanic rocks is apparently confined to continental regions and is a manifestation of significant energy input into the continental crust over extended time periods. In the western United States, such magmatism occurs predominantly in extensional settings in the Cenozoic Great Basin and TransPecos (west Texas) volcanic provinces. It is particularly prolific in the late Cenozoic Snake River Plain-Yellowstone province that forms a time-transgressive ‘hot spot’ track across southern Idaho, where rhyolites were extruded as large lava flows and even larger ignimbrites. Volumes of individual eruptions range up to at least 100 km3 for the lava flows and to as much as 3,000 km3 for the ignimbrites. Cumulative volumes of silicic magma produced likely exceed 105 km3, making this province one of the most prolific rhyolite outpourings on Earth. These rhyolites are characterized by high magmatic temperatures (sometimes exceeding 1,000°C), anhydrous phenocryst assemblages, low oxygen fugacities, and A-type trace element chemistry. This paper constitutes part of a special issue dedicated to Bill Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites. Editorial responsibility: J Stix M. McCurry (*) Department of Geosciences, Idaho State University, Pocatello, ID 83209, USA e-mail: [email protected] E. H. Christiansen Department of Geological Sciences, Brigham Young University, Provo, UT 84602, USA e-mail: [email protected] W. P. Leeman National Science Foundation, Arlington, VA 22203, USA e-mail: [email protected]
In all these respects the “anorogenic” rhyolites contrast sharply with silicic magmas from “orogenenic” settings (i.e., convergent margins and mid-Cenozoic calcalkaline silicic magmas of the Great Basin and Colorado Plateau including the Indian Peak, Central Nevada, San Juan, Mogollon-Datil, Sierra Madre and similar volcanic fields). The large scale of this anorogenic magmatism has important impacts in terms of potential volcanic hazards, climate change, and ore deposition, as well as implications regarding lithospheric modification. Thus, understanding the processes behind this magmatism is of particular importance with regard to the nature and flux of mantle-derived magma inputs into the crust, the eruptive behavior of the magmas, and overall effects on crustal growth and evolution. A fundamental question concerns the relative contributions of lithospheric extension versus sub-lithospheric processes (i.e., related to the low seismic velocity mantle or mantle plume which underlies Yellowstone today (Yuan and Dueker 2005) in producing these magmas. These and related topics are the subject of this special issue that is dedicated to Bill Bonnichsen, recently retired from the Id
Data Loading...
