Petrology, geochemistry, S, Cl and F abundances, and S oxidation state of sideromelane glass shards from Pleistocene ash layers north and south of Gran Canaria (ODP Leg 157) |
| |
| Authors: | Andrey A Gurenko Hans-Ulrich Schmincke |
| |
| Institution: | (1) GEOMAR Research Center, Department of Volcanology and Petrology, Wischhofstrasse 1–3, D-24148 Kiel, Germany; tel: (49-431) 600-2136; fax: (49-431) 600-2924; e-mail: agurenko@geomar.de, DE |
| |
| Abstract: | Major elements, S, F, Cl concentrations and relative proportions of S6+ to total S were analyzed with electron microprobe in sideromelane glass shards from Pleistocene volcaniclastic sediments
drilled during ODP Leg 157. Glasses are moderately to strongly evolved and represent a spectrum from alkali basalt, basanite
and nephelinite through hawaiite, mugearite and tephrite to phonolitic tephrite. Measured S6+/ΣS (0.03–0.98) and calculated Fe2+/Fe3+ (2.5–5.8) ratios in the melt yield preeruptive redox conditions ranging from NNO−1.4 to NNO+2.1. The morphology of the glass
shards, variations of S and Cl concentrations (0.010–0.127 wt% S, 0.018–0.129 wt% Cl), calculated preeruptive temperatures
(1030–1200 °C) and oxygen fugacities suggest that glasses deposited even within the same ash layers have diverse origin and
may have resulted from both submarine and subaerial eruptions. Most vesicle-free glasses are characterized by high concentrations
of S and represent undegassed or slightly degassed submarine lavas, whereas vesiculated glasses with low concentrations of
S and Cl are strongly degassed and can be ascribed to the eruptions in shallow water or on land. Sideromelane glass shards
at Sites 953 are thought to have resulted from submarine eruptions northeast of Gran Canaria, glasses at Site 954 represent
mostly volcaniclastic material of shallow water submarine and subaerial eruptions on Gran Canaria and Tenerife, and glasses
deposited at Site 956 resulted from submarine or explosive eruptions on Tenerife.
Received: 8 April 1997 / Accepted: 27 October 1997 |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
