Insights from quartz cathodoluminescence zoning into crystallization of the Vinalhaven granite,coastal Maine |
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Authors: | R A Wiebe D A Wark D P Hawkins |
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Institution: | (1) Department of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17603, USA;(2) Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA;(3) Department of Geosciences, Denison University, Granville, OH 43023, USA |
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Abstract: | The Vinalhaven intrusive complex provides field and petrographic evidence for multiple replenishments of mafic and silicic
magmas, mingling and limited mixing, and rejuvenation of granite. Quartz in granitic rocks preserves a record of those processes,
in the form of cathodoluminescence (CL) zoning, which is related to concentration of titanium, and to temperature of crystallization
using the new TitaniQ (Ti in quartz) geothermometer. Injection of mafic melts into partly crystalline Vinalhaven granite resulted
in partial quartz resorption followed by higher-temperature growth from H2O-undersaturated melt. This is shown by steep, rimward increases in CL intensity and Ti content across discordant boundaries
that truncate older growth zones. Quartz zoning in granite affected by mafic magmas displays large rimward jumps in Ti content,
whereas quartz in granitic feeders and in granite far from mafic rocks typically displays broad rims with decreasing Ti contents,
consistent with slow cooling without thermal disruptions due to mafic recharge. |
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