Chronology of multiphase emplacement of the Salmi rapakivi granite-anorthosite complex, Baltic Shield: implications for magnetic evolution
Article Abstract:
U-Pb dating of 18 rock specimens that symbolize major rock groups of the 4000 km(sup2) Salmi anorthosite-rapakivi granite complex and its satellite Uljalegi pluton, southeastern Baltic (Fennoscandian) Shield showed the occurrence of six temporary discrete episodes of igneous activity within a period of 17 million years. The duration of the cooling and crystallization of magmas and of zircon were compared to the accuracy of dating of +/-1-2 million years, and was found to be insignificant. Results show that dispersing of U-Pb ages between igneous states may closely resemble magma emplacement intervals.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1997
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Ordering and exsolution processes in Or-rich alkali feldspar megacrysts from the Eldzhurtinskiy granite (Caucasus)
Article Abstract:
Two types of alkali feldspar megacrysts in the Eldzhurtinskiy granite complex, Central Caucasus, reveal the differences in the cooling history between the upper and lower part of the rock. The megacrysts from the upper part are unordered and coherently exsolved, showing fine-scale regular orthoclase and albite-rich lamellae. Broad albite-rich lamellae and higher (Al, Si) ordering within the alkali feldspars characterize the lower part. Uniform cooling under dry conditions for the upper part and wet conditions for the lower resulted in a sharp boundary between the two.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Ion microprobe analysis of oxygen isotope ratios in quartz from Skye granite: healed micro-cracks, fluid flow, and hydrothermal exchange
Article Abstract:
Ion microprobe analysis of the oxygen isotope ratios in quartz in the hydrothermally altered granite from the Isle of Skye, Scotland, suggests that the quartz grains are highly heterogeneous and not equilibrated. Digitized cathodoluminescence images indicate magmatic zoning and brittle fracturing. Low oxygen isotope values are correlated to one set of healed cracks. Solution and reprecipitation along fractures allowed quartz to exchange oxygen isotopes. A model for a heterogeneous, anisotropic and crack-controlled flow of hydrothermal fluids is presented.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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