Skip to main content Accessibility help
×
Hostname: page-component-7c8c6479df-27gpq Total loading time: 0 Render date: 2024-03-28T12:13:43.570Z Has data issue: false hasContentIssue false
This chapter is part of a book that is no longer available to purchase from Cambridge Core

20 - Mineral reactions involving H2O and CO2

Anthony Philpotts
Affiliation:
Yale University, Connecticut
Jay Ague
Affiliation:
Yale University, Connecticut
Get access

Summary

INTRODUCTION

Most prograde metamorphic reactions involve dehydration or decarbonation. The large increase in entropy that accompanies the liberation of a volatile phase from a mineral ensures that rising metamorphic temperatures will favor reactions that produce a separate vapor phase. The properties of this phase are critical in determining which metamorphic reactions take place and under what conditions they occur. We have already seen in the simple example of the model metamorphic terrane treated in Chapter 18 that very different conclusions about the conditions of metamorphism can be reached depending on the assumptions made about the composition of the fluid phase (Fig. 18.4). The purpose of this chapter is to outline some of the important principles governing metamorphic reactions that involve a volatile phase.

The fluid phase in most metamorphic rocks is dominated by H2O and CO2. Both of these are initially derived almost entirely from the atmosphere (meteoric). Water is incorporated by minerals, such as the clays, during the weathering of rocks or the diagenesis of sediments. Carbon dioxide may also be similarly incorporated with the formation of calcite or dolomite. But the largest amount of CO2 enters metamorphic rock as calcite of biological origin formed from the shells of organisms. Both H2O and CO2 are trapped directly as pore fluid, but during compaction and diagenesis of sediment most of this is expelled. The fluid phase in metamorphic rocks is therefore derived largely from the breakdown of minerals rather than from the initially trapped pore fluid.

Type
Chapter
Information
Publisher: Cambridge University Press
Print publication year: 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Save book to Kindle

To save this book to your Kindle, first ensure coreplatform@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×