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Mineralogy, geochemistry and Sr-isotopes in orendites from South Tuscany, Italy; constraints on their genesis and evolution

Sandro Conticelli, Piero Manetti and Stefano Menichetti
Mineralogy, geochemistry and Sr-isotopes in orendites from South Tuscany, Italy; constraints on their genesis and evolution
European Journal of Mineralogy (December 1992) 4 (6): 1359-1375

Abstract

The Orciatico (ORC) and Montecatini Val di Cecina (MVC) volcanic rocks are composed of plagioclase-free lamproitic assemblages with abundant phlogopite, sanidine, clinopyroxene, olivine and apatite and minor ilmenite, magnesiochromite and K-richterite. Both suites of rocks are rich in SiO (sub 2) (56-59%), incompatible elements and radiogenic Sr and have high mg values (72-76), Ni (150-250 ppm) and Cr (350-450 ppm); in contrast, they are low in Al (sub 2) O (sub 3) (10-12%), CaO (3-4%) and Na (sub 2) O (1-1.5%). The relatively primitive ORC rocks probably did not undergo any differentiation during their ascent to the surface; the MVC magma was probably derived from the ORC magma by assimilation and fractional crystallization processes. The ORC rocks have high (super 87) Sr/ (super 86) Sr and low (super 143) Nd/ (super 144) Nd ratios as well as very high contents of incompatible elements. The proposed mantle source was depleted in basaltic elements before the enrichment in incompatible elements and radiogenic isotopes. There are similarities with the rocks of the Roman comagmatic province and those from SE Spain. Results of 40 EPMA silicate analyses are tabulated.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 6
Title: Mineralogy, geochemistry and Sr-isotopes in orendites from South Tuscany, Italy; constraints on their genesis and evolution
Affiliation: Universita degli Studi di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Pages: 1359-1375
Published: 199212
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 60
Accession Number: 1995-056255
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables, sketch maps
N42°19'60" - N44°19'60", E09°40'00" - E12°25'00"
Secondary Affiliation: Max Planck Institut fuer Chemie, DEU, Federal Republic of GermanyAmministrazione Provinciale di Pisa, ITA, Italy
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199520
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