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Contrasting Mineralizing Processes in Volcanic-Hosted Graphite Deposits

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Luque del Villar, Francisco Javier and Barrenechea, José F. and Ortega Menor, Lorena and Rodas, Magdalena and Millward, David (2009) Contrasting Mineralizing Processes in Volcanic-Hosted Graphite Deposits. In Smart Science for Exploration and Mining, Proceedings of the Tenth Biennial SGA Meeting. The Economic Geology Research Unit, Townsville, Australia, pp. 998-990. ISBN 9780980558685.

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Abstract

The only two known graphite vein-deposits hosted by volcanic rocks (Borrowdale, United Kingdom, and Huelma, Southern Spain) show remarkable similarities and differences. The lithology, age of the magmatism and geodynamic contexts are distinct, but the mineralized bodies are controlled by fractures. Evidence of assimilation of metasedimentary rocks by the magmas and hydrothermal alteration are also common features to both occurrences. Graphite morphologies at the Borrowdale deposit vary from flakes (predominant) to spherulites and cryptocrystalline aggregates, whereas at Huelma, flaky graphite is the only morphology observed. The structural characterization of graphite indicates a high degree of ordering along both the c axis and the basal plane. Stable carbon isotope ratios of graphite point to a biogenic origin of carbon, most probably related to the assimilation of metasedimentary rocks. Bulk į13C values are quite homogeneous in both occurrences, probably related to precipitation in short time periods. Fluid inclusion data reveal that graphite precipitated from C-O-H fluids at moderate temperature (500 ºC) in Borrowdale and crystallized at high temperature from magma in Huelma, In addition, graphite mineralization occurred under contrasting fO2 conditions. All these features can be used as potential exploration tools for volcanic-hosted graphite deposits.


Item Type:Book Section
Uncontrolled Keywords:Graphite deposits, volcanic rocks, C-O-H fluids
Subjects:Sciences > Geology
ID Code:44866
Deposited On:28 Sep 2017 10:51
Last Modified:11 Dec 2018 08:46

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