CGRG Bibliography of Canadian Geomorphology
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Author : Dixon, J.E.; Filiberto, J.; Moore, J.M.; and Hickson, C.J.
Date : 2000.
Title : Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia: Implications for mantle volatiles and ice sheet thickness.
Publication : Volcano/Ice Interaction on Earth and Mars, August 13-15, 2000, University of Iceland, Reykjavík, Iceland. Abstract Volume. Edited by: Gulick, V.C.; and Gudmundsson, M.T.
Issue :
Page(s) : 11.
Abstract
We measured dissolved water and carbon dioxide concentrations in glasses from Tanzilla Mtn., an exposed subglacial volcano from the Tuya region, north central British Columbia. Tuya formation begins with non-explosive eruptions of pillow basalt and interpillow hyaloclastites. As the volcano grows, the ice/water depth progressively decreases until the overlying ice melts through to form a lake. The eruption then changes to phreatic or explosive resulting in layers of glassy tephra on top of the pillows. If the eruption continues, crater walls build up above the water level and subaerial lava flows cap the sequence. Based on S analyses, Tanzilla is the least degassed of the 8 tuyas studied and did not reach the subaerial phase. Dissolved water (0.49- 0.92 wt%) and carbon dioxide (0-72 ppm) are similar to those observed in shallow oceanic islands, such as Loihi. Vapor saturation pressures calculated from dissolved water and carbon dioxide contents range from 35 to 200 bars with glasses collected at the base of the tuya yielding the highest estimated equilibration pressure. A pressure of 200 bars corresponds to an ice thickness of ~2 (±~0.5) km overlying the nascent Tanzilla tuya, consistent with Cordilleran ice thickness predicted by the ICE-4G model. Water concentrations correlate positively with other incompatible elements, such as P2O5. The Tanzilla data overlap data from other Pacific seamounts (e.g., Loihi) and enriched-MORB implying that metasomatic enrichment of the mantle source regions for the tuyas involved a melt and not a hydrous fluid phase.
Bibliography of Canadian Geomorphology