Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Key factors controlling massive graphite deposition in volcanic settings; an example of a self-organized critical system

F. J. Luque, L. Ortega, J. F. Barrenechea, J. M. Huizenga and D. Millward
Key factors controlling massive graphite deposition in volcanic settings; an example of a self-organized critical system
Journal of the Geological Society of London (May 2012) 169 (3): 269-277

Abstract

Massive graphite deposition resulting in volumetrically large occurrences in volcanic environments is usually hindered by the low carbon contents of magmas and by the degassing processes occurring during and after magma emplacement. In spite of this, two graphite deposits are known worldwide associated with volcanic settings, at Borrowdale, UK, and Huelma, Spain. As inferred from the Borrowdale deposit, graphite mineralization resulted from the complex interaction of several factors, so it can be considered as an example of self-organized critical systems. These factors, in turn, could be used as potential guides for exploration. The key factors influencing graphite mineralization in volcanic settings are as follows: (1) an unusually high carbon content of the magmas, as a result of the assimilation of carbonaceous metasedimentary rocks; (2) the absence of significant degassing, related to the presence of sub-volcanic rocks or hypabyssal intrusions, acting as barriers to flow; (3) the exsolution of a carbon-bearing aqueous fluid phase; (4) the local structural heterogeneity (represented at Borrowdale by the deep-seated Burtness Comb Fault); (5) the structural control on the deposits, implying an overpressured, fluid-rich regime favouring a focused fluid flow; (6) the temperature changes associated with fluid flow and hydration reactions, resulting in carbon supersaturation in the fluid, and leading to disequilibrium in the system. This disequilibrium is regarded as the driving force for massive graphite precipitation through irreversible mass-transfer reactions. Therefore, the formation of volcanic-hosted graphite deposits can be explained in terms of a self-organized critical system.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 169
Serial Issue: 3
Title: Key factors controlling massive graphite deposition in volcanic settings; an example of a self-organized critical system
Affiliation: Universidad Complutense de Madrid, Departamento Cristalografia y Mineralogia, Madrid, Spain
Pages: 269-277
Published: 201205
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 61
Accession Number: 2012-056746
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N54°31'45" - N54°31'45", W03°08'45" - W03°08'45"
Secondary Affiliation: North-West University, ZAF, South AfricaBritish Geological Survey, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201229
Close Modal

or Create an Account

Close Modal
Close Modal