Monomineralic Glomerocrysts: Textural Evidence for Mineral Resorption during Crystallization of Igneous Rocks

Abstract

Monomineralic aggregates or glomerocrysts are a distinctive feature of many igneous rocks. Those with crystals joined along prominent euhedral crystal faces form by synneusis while the mineral is crystallizing. Other glomerocrysts, comprised of crystals joined along irregular, embayed margins, arguably formed while the crystals were being resorbed. A model for glomerocryst formation during mineral resorption is described. During resorption, a boundary-layer melt, which envelops the dissolving crystals, is produced. When two or more dissolving crystals come into close proximity, the intervening portion their respective boundary-layer melts becomes isolated from chemical communication with the surrounding granitic liquid. Contributions from both dissolving crystals to this isolated portion of the boundary layer melt creates a melt composition that eventually becomes supersaturated with respect to the dissolving crystals. This results in crystallization of new material from the intervening melt that bonds the partially resorbed crystals together. Any process that causes mineral resorption, such as a change in intensive parameters (e.g., P, T, aH2O), can lead to glomerocyst formation. Such glomerocrysts can be used to define pressure-temperature paths of igneous rocks that are compatible with mineral resorption.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Crystallization; Glomerocryst; Igneous Rock; Mineral Aggregate; Mineral Resorption

International Standard Serial Number (ISSN)

0022-1376

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1993 University of Chicago, All rights reserved.

Publication Date

01 Jul 1993

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