Cooling rates of basaltic hyaloclastites and pillow lava glasses from the HSDP2 drill core

doi:10.1016/j.gca.2008.11.023

Geochimica et Cosmochimica Acta

Volume 73, Issue 4, 15 February 2009, Pages 1052-1066

https://doi.org/10.1016/j.gca.2008.11.023 Get rights and content

Abstract

Cooling rates have been determined for basaltic glasses from different depths of the submarine section of the drill core recovered in the 1999 phase of Hawaii Scientific Drilling Project (HSDP2). The glasses include degassed blocky hyaloclastite clasts and undegassed pillow rims. The degassed glassy clasts were generated in subaerial or shallow submarine environments, during explosive interactions between lava and seawater, before eventual deposition under water. The volatile contents of the glassy pillow rims are consistent with eruption and quenching in water several hundred metres deep. The cooling rates have been calculated from the calorimetric properties of the glass across the glass transition. The heat capacity (c_p) of each sample was measured during several cycles of heating from room temperature to temperatures above their glass transition using a differential scanning calorimeter (DSC). Their compositions did not change during the thermal treatment, a prerequisite for successful c_p measurements, although the glasses with higher H₂O contents became more opaque and their mid-IR spectra changed. Each c_p-T path exhibits the now classic features of the glass transition; glassy and liquid states separated by a hysteresis marking the transition. After experiencing the same experimental thermal history the glass transition occurs at lower temperatures in glasses with higher H₂O contents. Except for one sample, the c_p-T path measured on initial heating also releases energy stored during the natural quench, which is not recovered during subsequent experimental cooling. The energy stored in the HSDP2 glasses is much less than that observed in hyperquenched natural and synthetic glasses. Even so, the Tool–Narayanaswamy enthalpy relaxation geospeedometer, usually used to determine the cooling rates in volcanic glasses, is unable to deal with this energy release. For those samples that exhibit this feature an alternative method, developed for hyperquenched glasses, is applied. This uses the energy released to calculate T_f, from which the cooling rate is calculated. The degassed blocky hyaloclastite clasts exhibit cooling rates 0.1–72.2 K s⁻¹, while the undegassed pillow rims span 0.2–46.4 K s⁻¹. The fastest cooling rates are consistent with the cooling of lava bodies in seawater. The wide variation for both types of glass could reflect quenching at different distances from the basalt-seawater interface. However, for the degassed hyaloclastite clasts the range could indicate that the clasts were generated by different processes operating during the explosive interaction between lava and seawater in the littoral zone. In the undegassed pillow lavas, glassy rims may have been reheated, giving rise to more complex, slower, thermal histories, as a result of latent heat released during the crystallisation of pillow interiors, or flow replenishment. Both types of glass may also have experienced reheating from succeeding flows or deposits. Compared to deep-sea limu o Pele hyaloclastite fragments, whose hyperquench rates indicate simultaneous cooling and fragmentation, the shallow blocky hyaloclastite clasts may have formed during post-cooling brittle fragmentation.

Introduction

Cooling rates of volcanic glasses can be quantified by geospeedometers that use the calorimetric properties of the glass (Wilding et al., 1995) or the speciation of water contained in the glass (Zhang et al., 1997, Zhang et al., 2000, Xu and Zhang, 2002). In this study we examine the suitability of these geospeedometers for determining the cooling rates of basaltic glass from submarine emplaced units in the drill core recovered during the 1999 phase of the Hawaii Scientific Drilling Project (HSDP2) (Hawaii Scientific Drilling Project, 2000, DePaolo et al., 2001, Garcia et al., 2007). The glasses include degassed blocky hyaloclastite clasts erupted and quenched in subaerial or shallow submarine environments before deposition in water, and glassy pillow rims with volatile contents that are consistent with eruption and quenching in water several hundred metres deep (Seaman et al., 2004). Each sample was compared before and after the calorimetry experiments to ensure that no compositional changes had occurred. The variation in H₂O between the glasses allows the effect H₂O has on the calorimetric properties to be investigated. The study compares the calculated cooling rates, and discusses the implications they have for quenching mechanisms in the different environments.

Section snippets

The glass transition

The basis for using the calorimetric properties and the water speciation in glass to determine its cooling rate is built around the glass transition theory. The glass transition is the temperature interval across which the properties of a melt change from those of a liquid-like state to those of a solid-like state (Dingwell and Webb, 1989, Dingwell and Webb, 1990). It can be considered in terms of relaxation time, which can be approximated by Maxwell’s law of linear viscoelasticity (Maxwell,

Glasses from the HSDP2 drill core

The samples used in this study were taken from the drill core recovered by the 1999 (HSDP2) phase of the Hawaii Scientific Drilling Project at Hilo, Hawaii. This phase of drilling reached a depth of 3097.7 mbsl. At the drilling site core loggers divided the HSDP2 drill core into 345 lithological units (Hawaii Scientific Drilling Project, 2000, DePaolo et al., 2001, Garcia et al., 2007). The core is largely made of submarine emplaced volcanic material with compositions characteristic of Mauna

Calorimetry

The specific heat capacities (c_p) of the glass samples were measured using a differential scanning calorimeter (Netzsch^® DSC 404C Pegasus) at the Department of Earth and Environmental Sciences, University of Munich. Prior to the series of measurements required to calculate c_p, the heat flow of an aliquot from each sample was heated at either 5 or 20 K min⁻¹, depending on the planned thermal treatment, to check how each sample would behave. This also allowed the temperature to which the sample had

Sample changes during calorimetry experiments

Major elements and volatile compositions of glasses from the HSDP2 drill core are reported in Stolper et al. (2004). Table 1, Table 2 show, where glasses have been taken from the same part of the drill core, that the major element concentrations measured in this study are generally within 1σ of the glass analyses of Stolper et al. (2004). The H₂O data for two hyaloclastite samples with less than 0.10 wt.% H₂O also agree well. However, in three pillow lava samples with higher H₂O contents, this

Dependency of glass transition temperature on water content

The glass transition temperature (T_g) is a single temperature within the glass transition interval that is defined in a consistent manner from the c_p-T trace measured during each heating. T_g can be defined in a number of ways. In this study we define it as the temperature at which the extrapolated glassy state (c_pg), defined by: $c_{pg} = a + bT + {cT}^{- 2}$ where a, b and c are constants and T temperature, intersects the tangent to the maximum gradient of the rising c_p curve on the low temperature side of the

Curve fitting (Tool–Narayanaswamy relaxation geospeedometer)

Most previous studies (Wilding et al., 1995, Wilding et al., 1996, Wilding et al., 2000, Wilding et al., 2004, Gottsmann and Dingwell, 2001a, Gottsmann and Dingwell, 2001b, Gottsmann and Dingwell, 2002, Gottsmann et al., 2004) that have calculated the cooling rates of volcanic glass from calorimetry data have used the T–N geospeedometer (Tool, 1946, Narayanaswamy, 1971). This relates c_p, or the derivative of enthalpy (ΔH/ΔT), to changes in fictive temperature (ΔT_f/ΔT). T_f can be expressed as a

Cooling rates

For sample SR0815-3.80, where the drop in c_p is absent on initial heating, the T–N geospeedometer produces a cooling rate of 0.2 (±0.05) K s⁻¹. For sample SR0855-0.60c, where the drop is small enough to be modelled (Fig. 5a), the geospeedometer gives a cooling rate of 0.6 (± 0.08) K s⁻¹.

The cooling rate for SR0855-0.60c can also be calculated by the area-matching method, combining the approaches of Moynihan et al. (1976) and Yue et al. (2002). The method gives a cooling rate of 0.1 K s⁻¹, which is

Conclusions

The cooling rates of basaltic glasses from blocky hyaloclastite clasts and pillow rims from the submarine section of the HSDP2 drill core have been calculated using their calorimetric properties. The hyaloclastite clasts are degassed, indicating eruption and quenching in a subaerial or shallow submarine environment before becoming deposited under water. The pillow lava glasses, on the other hand, all have volatile contents consistent with eruption and quenching at water depths of several

Acknowledgments

The authors are very grateful for the thorough reviews provided by J. Gottsmann, W. Mueller, and two anonymous reviewers, and the editorial handling by J.K. Russell. The work was funded by Deutsche Forschungsgemeinschaft, ICDP program, project DI 431/21-1, and during its completion ARLN received financial support from the Volcano Dynamics EU Research Training Network (HPRN-CT-2000-00060) and a JSPS Fellowship. We would also like to thank C. Seaman and E. Stolper for allowing access to the HSDP2

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Cooling rates of basaltic hyaloclastites and pillow lava glasses from the HSDP2 drill core

Abstract

Introduction

Section snippets

The glass transition

Glasses from the HSDP2 drill core

Calorimetry

Sample changes during calorimetry experiments

Dependency of glass transition temperature on water content

Curve fitting (Tool–Narayanaswamy relaxation geospeedometer)

Cooling rates

Conclusions

Acknowledgments

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

J. Volcanol. Geotherm. Res.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Mar. Geol.

J. Volcanol. Geotherm. Res.

Comput. Geosci.

Chem. Geol.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

J. Volcanol. Geotherm. Res.

Chem. Geol.

J. Volcanol. Geotherm. Res.

Earth Planet. Sci. Lett.

Chem. Phys. Lett.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Kinetics of enthalpy relaxation at the glass transition in ternary telluride glasses

J. Am. Ceramic Soc.

Strong and fragile liquids

Thermodynamic properties of synthetic sapphire (α-Al2O3), Standard Reference Material 720 and the effect of temperature-scale differences on thermodynamic properties

J. Phys. Chem. Ref. Data

Nonexponential relaxations in strong and fragile glass formers

J. Chem. Phys.

Thermodynamic properties of synthetic sapphire (α-Al₂O₃), Standard Reference Material 720 and the effect of temperature-scale differences on thermodynamic properties