T208 Emplacement of Upper Crustal Magmatic Intrusions: Field Studies of Laccoliths, Sills, and Subvolcanic Plugs (Posters)

Tuesday, 21 October 2014
9:00 AM - 6:30 PM
Exhibition Hall C

MAGMATIC DYNAMICS OF PARASITIC ERUPTIVES: INSIGHTS INTO A LATE STAGE CONDUIT AND VENT FILLING INTRUSION

Paper number: T208-15
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Magmatic and textural relationships observed at Pa Bay reveal new insights into parasitic volcanism at the Akaroa Volcanic Complex, New Zealand. Akaroa is an extinct intraplate composite strato-shield volcano, of eastern Banks Peninsula on New Zealand's South Island (Hampton & Cole, 2009). While some elements of the physical volcanology and geochemistry of Banks Peninsula have been previously explored (Hampton & Cole, 2009; Timm et al., 2009; Ring & Hampton, 2012; Johnson, 2012; Metcalfe, 2013), the deposits at Pa Bay provide exceptional exposure and insight into the magmatic plumbing system of a recently discovered flank vent (Burgi 2013). Here, scoria cone deposits overlie fissure-fed eruption deposits, both of which have been cross-cut by a late stage volcanic intrusive body. Geological mapping supported by major element geochemical data and petrographic textural analyses suggests the intrusive body was a subvolcanic plug infilling the volcanic conduit system of the scoria cone. Chemical and textural variations within the intrusive plug, including the presence of mafic enclaves and indicative phenocryst textures, suggest that magma mingling and mixing were important processes during and preceding emplacement. This study provides insight into intrusive contact relationships within scoria cones and the magmatic processes that drive flank volcanism.