Jurassic volcanic glass in the Ferrar Large Igneous Province of Antarctica preserves evidence for hydration by glacial meltwater
Abstract
The Butcher Ridge Igneous Complex (BRIC) is an 6000 km3 hypabyssal intrusion within the Jurassic Ferrar Large Igneous Province of Antarctica. BRIC rocks vary geochemically from basaltic andesite to rhyolite and preserve enigmatic rhythmic meter-scale layering. Layering is observed in a 1 km long vitrophyre body, units of alternating vitrophyre and crystalline layers, and units of alternating crystalline layers. Individual layers in all units are laterally continuous for hundreds of meters and generally range from 1 to 3 meters thick. Petrographic observations indicate crystalline layers formed by the complete devitrification of glass to form K-feldspar and quartz. Vitrophyre rocks of the BRIC contain abundant geochemical and textural evidence for pervasive alteration during secondary hydration. In-situ FTIR water content and speciation data and whole-rock hydrogen isotope measurements on BRIC glasses indicate high molecular water contents and highly depleted δD values, consistent with hydration by glacial meteoric/environmental water syn- or post-emplacement of the intrusion in the Early Jurassic. Together, these results suggest that the BRIC records a remarkable geologic history including formation of large volumes of volcanic glass, rhythmic meter-scale layering, and pervasive hydration by meteoric fluids.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V23J0182N
- Keywords:
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- 8404 Volcanoclastic deposits;
- VOLCANOLOGYDE: 8424 Hydrothermal systems;
- VOLCANOLOGYDE: 8427 Subaqueous volcanism;
- VOLCANOLOGYDE: 8445 Experimental volcanism;
- VOLCANOLOGY