A clinopyroxene–basalt geothermobarometry perspective of Columbia Plateau (NW-USA) Miocene magmatism

  1. Graziella Caprarelli1,
  2. Stephen P. Reidel2

Article first published online: 22 APR 2005

DOI: 10.1111/j.1365-3121.2005.00611.x

Issue

Terra Nova

Terra Nova

Volume 17, Issue 3, pages 265–277, June 2005

Additional Information

How to Cite

Caprarelli, G. and Reidel, S. P. (2005), A clinopyroxene–basalt geothermobarometry perspective of Columbia Plateau (NW-USA) Miocene magmatism. Terra Nova, 17: 265–277. doi: 10.1111/j.1365-3121.2005.00611.x

Author Information

  1. 1

    Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, Australia

  2. 2

    Pacific Northwest National Laboratory, MS K6-81, PO Box 999, Richland, WA 99352, USA

*Graziella Caprarelli, Department of Environmental Sciences, University of Technology, Sydney, PO Box 123, Broadway, NSW 2007, Australia. Tel.: 00 61 2 9514 1776; fax: 00 61 2 9514 1755; e-mail: Graziella.Caprarelli@uts.edu.au

Publication History

  1. Issue published online: 3 MAY 2005
  2. Article first published online: 22 APR 2005
  3. Received 16 September 2004; revised version accepted 3 January 2005

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Abstract

The origin of NW-USA Columbia River Basalt Group Miocene magmatism and its relation to tectonism has been widely debated and is still open to study. We investigated the pre-eruptive evolution of the magmas, to constrain pressures and temperatures of the ascending magmas, and plumbing conditions. We determined major element concentrations of 17–6 Ma tholeiites, and applied clinopyroxene – liquid geothermobarometry to calculate pre-eruptive pressures and temperatures. These ranged from 0 to 0.66 GPa and 1120 to 1222 °C, respectively, defining two age-related parallel trends in a P–T diagram. This indicates a consistent crustal evolution of the magmas, and records at least two distinct initial temperatures. Using clinopyroxene interdiffusion coefficients we estimated magma ascent speeds ≥ 0.6 km yr−1. Possible geological explanations for the calculated parameters are: lower-crust magma chamber processes; magmatism and tectonism feed-back consistent with an extensional environment.

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