Cooling rates and crystallization dynamics of shallow level pegmatite-aplite dikes, San Diego County, California

Pegmatites of the Pala and Mesa Grande Pegmatite Districts, San Diego County, California are typically thin, sheet-like composite pegmatite-aplite dikes. Aplitic portions of many dikes display pronounced mineralogical layering referred to as “line rock,” characterized by fine-grained, gamet-rich ban...

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Bibliographic Details
Published in:The American mineralogist 1999-05, Vol.84 (5), p.708-717
Main Authors: Webber, Karen L., Simmons, William B., Falster, Alexander U., Foord, Eugene E.
Format: Article
Language:English
Online Access:Get full text
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Summary:Pegmatites of the Pala and Mesa Grande Pegmatite Districts, San Diego County, California are typically thin, sheet-like composite pegmatite-aplite dikes. Aplitic portions of many dikes display pronounced mineralogical layering referred to as “line rock,” characterized by fine-grained, gamet-rich bands alternating with albite- and quartz-rich bands. Thermal modeling was performed for four dikes in San Diego County including the 1 m thick Himalaya dike, the 2 m thick Mission dike, the 8 m thick George Ashley dike, and the 25 m thick Stewart dike. Calculations were based on conductive cooling equations accounting for latent heat of crystallization, a melt emplacement temperature of 650 ℃ into 150 ℃ fractured, gabbroic country rock at a depth of 5 km, and an estimated 3 wt% initial H O content in the melt. Cooling to
ISSN:0003-004X
1945-3027
DOI:10.2138/am-1999-5-603