Magma Chamber Depths at Kverkfjoll volcanic system, Iceland and Connections to Recent Dyke Injection at Mt. Upptyppingar, Iceland.

Rifting along mid-ocean ridges (MOR) is facilitated by injection of dykes and magma chambers within the crust in rifting events which occur at discrete locations along the axis of a rift zone. These volcano-tectonic events in Iceland's rift zones are often accompanied by outpouring of lava at the Earth's surface. We have used mineral-melt equilbria relationships to determine the pressure and temperature of magmas erupted from the Kverkfjoll volcanic system, located along the eastern margin of the Northern Volcanic Zone (NVZ). This volcanic system consists of the central volcano, Kverkfjoll volcano and a series of fissure eruptions extending northward approximately 50 km to Mt. Upptyppingar, a large mound of hyaloclastites and pillow lavas. Pressures and temperatures were calculated for melts lying along the olivine, plagioclase and augite cotectic. Input data were published analyses of basaltic glass in samples of pillow lava, as well as samples of glass in melt inclusions in phenocrysts. The results provide evidence for partial crystallization at average pressures of 426 MPa and 822 MPa, corresponding to depths of 15 km and 29 km. We conclude that the sampled lavas were erupted from magma chambers at these depths. These depths are consistent with seismic data for recent swarms of microseismicity beneath Upptyppingar (February 2007 to May 2008). The seismic activity is interpreted to reflect influx of magma into a dyke at a depth of 15 to 18 km. The seismic unrest at Upptyppingar might signal a rifting episode in the NVZ of Iceland. The latter accommodates the full 20 mm/yr spreading in this portion of the mid-Atlantic Ridge, but it has been over 20 years since the last major rifting episode in the NVZ at Krafla. Eruption of magmas from deep chambers will promote rapid degassing and may lead to explosive activity that could inject volcanic aerosols sufficiently high in the atmosphere to affect the Earth's climate.