| Abstract: | Dissolved H2O, CO2, S and Cl concentrations were measured in glasses from Tanzilla Mountain, a 500 m-high, exposed subglacial volcano from the Tuya-Teslin region, north central British Columbia, Canada. The absence of a flat-topped subaerial lava cap and the dominance of pillows and pillow breccias imply that the Tanzilla Mountain volcanic edifice did not reach a subaerial eruptive phase. Lavas are dominantly tholeiitic basalt with minor amounts of alkalic basalt erupted at the summit and near the base. Tholeiites have roughly constant H2O (c.0.56 ?? 0.07 wt%), CO2 (<30 ppm), S (980 ?? 30 ppm) and Cl (200 ?? 20 ppm) concentrations. Alkalic basalts have higher and more variable volatile concentrations that decrease with increasing elevation (0.62-0.92 wt% H2O, <30 ppm CO2, 870-1110 ppm S and 280-410 ppm Cl) consistent with eruptive degassing. Calculated vapour saturation pressures for the alkalic basalts are 36 to 81 bars corresponding to ice thicknesses of 400 to 900 m. Maximum calculated ice thickness (c. 1 km) is at the lower end of the range of predicted maximum Fraser glaciation (c. 1-2 km), and may indicate initiation of volcanism during the waning stages of glaciation. Temporal evolution from tholeiitic to alkalic compositions may reflect compositional gradients within a melting column, instead of convective processes within a stratified magma chamber. The mantle source region for the subglacial volcanoes is enriched in incompatible elements similar to that for enriched mid-oceanic ridge basalt (e.g. Endeavour Ridge) and does not contain residual amphibole. Thus, metasomatic enrichment most likely reflects small degree partial melts rather than hydrous fluids. |
| Genre: | Article |
| ProdID: | 70023829 |
| Citation Author: | Dixon, J. E.; Filiberto, J. R.; Moore, J. G.; Hickson, C. J. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 271 |
| Citation Issue: | 202 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Geological Society Special Publication |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 17 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia (Canada): Implications for ice sheet thickness and mantle volatiles; 2002; Article; Journal; Geological Society Special Publication; Dixon, J. E.; Filiberto, J. R.; Moore, J. G.; Hickson, C. J. |
| Citation Start Page: | 255 |
| Citation Volume: | |
| Citation Year: | 2002 |
| Type: | citation/reference |
| Text: | Volatiles in basaltic glasses from a subglacial volcano in northern British Columbia (Canada): Implications for ice sheet thickness and mantle volatiles; 2002; Article; Journal; Geological Society Special Publication; Dixon, J. E.; Filiberto, J. R.; Moore, J. G.; Hickson, C. J. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Tue, 1 Jan 2002 00:00 -0600 |
| Publisher: | |
