Viscosity of evolving magmas: a case study of the Glass House Mountains, Australia

Sharon L Webb

doi:10.1007/s00445-021-01495-8

Abstract

The viscosity of the remelted rock compositions of the Glass House Mountains, SE Queensland, Australia, has been determined via micro-penetration in the high-viscosity regime (108–1013 Pa s). The heat capacity of these melts has also been determined from room temperature to above the glass transition. The combination of these two data sets allows the fitting of the viscosity data by the Adam-Gibbs equation using the configurational heat capacity Cpconf(Tg12) and configurational entropy Sconf(Tg12). The resulting fit parameters allow the robust extrapolation of the viscosity data to higher temperature and viscosities of 10–4 Pa s. This data can now be used in the discussion of the emplacement of the magmas of the plugs, laccoliths, sills and dykes that form the Glass House Mountains complex and the plate motion and the plume responsible for the volcano plugs. The large increase in viscosity of the evolving magma and the resulting decrease in discharge rate of the volcanic vents suggest that very little magma appeared as extrusive lavas or pyroclastic material and that the Glass House Mountains are mainly remnants of intrusive bodies exposed by erosion.

Highlights

There is a growing interest in the 9–33 million years old plume track across Eastern Australia from Cape Hillsborough (QLD) to Cosgrove (Vic) (Cohen et al 2013; Davies et al 2015)
The viscosity of the melts is listed as a function of temperature in Table 3 and shown in Figs. 4 and 5 as a function of inverse temperature
For η0 the viscosity constant in Pa s and E the activation energy for flow in kJ m ol−1, T temperature in K and the gas constant R = 8.314 J mol−1 K−1 is fit to the data in the form log10

Summary

Introduction

There is a growing interest in the 9–33 million years old plume track across Eastern Australia from Cape Hillsborough (QLD) to Cosgrove (Vic) (Cohen et al 2013; Davies et al 2015). The Noosa-Maleny-Glass House Mountains complex (hereafter called GHM) is a small suite of volcanoes in SE Queensland that is associated with this plume track (see Fig. 1). The GHM volcanoes have been dated in the Oligocene at 26 million years (Cohen et al 2007). The shape of these plugs is similar to that of glass furnaces in Great Britain, the name given to them by Cook in 1770. Recent analysis of major and trace elements of rocks from the Glass House Mountains as well as Sr, Nd and Pb isotopic data by Shao et al (2015) has shown the GHM volcanoes to be the product of an evolving magma chamber with the magma compositions progressing from basaltic lava flows in the Editorial responsibility: K.V. Cashman

Methods

Results

Conclusion