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High-¹⁸O igneous rocks from the Tuscan Magmatic Province, Italy

Taylor, Hugh P., Jr. and Turi, Bruno (1976) High-¹⁸O igneous rocks from the Tuscan Magmatic Province, Italy. Contributions to Mineralogy and Petrology, 55 (1). pp. 33-54. ISSN 0010-7999. doi:10.1007/bf00372753.

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The ¹⁸O/¹⁶O ratios were measured for 60 rocks and coexisting minerals from the Plio-Pleistocene, calc-alkaline, Tuscan Magmatic Province, Italy. The δ¹⁸O values of these magmas were as follows: Elba, Giglio, and Montecristo granodiorites (11.4 to 12.1); M. Cimini rhyolites and trachytes (11.2 to 11.7); Roccastrada, S. Vincenzo, and M. Amiata rhyolites (12.3 to 13.4); and the Tolfa rhyolites and quartz latites (15.3 to 16.4). The latter are by far the highest δ¹⁸O values yet reported for primary volcanic rocks. The extremely high δ¹⁸O values in the Tuscan Province indicate that these magmas all formed by melting or large-scale assimilation of high-¹⁸O argillaceous sedimentary rocks, in agreement with previous evidence based on the high ⁸⁷Sr/⁸⁶Sr ratios and ubiquitous presence of cordierite. Low δ¹⁸O values (+5 to +6) were found in the feldspar, but not the quartz, of the small Porto Azzuro stock on Elba, as well as in the marginal facies of the M. Capanne stock, indicating that these bodies interacted with low-¹⁸O meteoric-hydrothermal fluids subsequent to solidification. The M. Cimini lavas apparently formed about 1 m.y. ago by mixing of high-¹⁸O Tuscan magmas containing large K feldspar crystals with potassic, undersaturated, low-¹⁸O magmas of the adjacent Roman Co-Magmatic Province. These large sanidine crystals did not completely equilibrate ¹⁸O/¹⁶O with the coexisting magma.

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Alternate Title:High-18O igneous rocks from the Tuscan Magmatic Province, Italy
Additional Information:© 1976 Springer. Received 13 August 1975. Accepted 01 November 1975. Publication of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, Contribution Number 2639.
Subject Keywords: Quartz; Assimilation; Mineral Resource; Volcanic Rock; Sedimentary Rock
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Caltech Division of Geological and Planetary Sciences2639
Issue or Number:1
Record Number:CaltechAUTHORS:20201014-153714444
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Official Citation:Taylor, H.P., Turi, B. High-18O igneous rocks from the Tuscan Magmatic Province, Italy. Contr. Mineral. and Petrol. 55, 33–54 (1976).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106078
Deposited By: George Porter
Deposited On:15 Oct 2020 22:31
Last Modified:16 Nov 2021 18:49

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