1. Plagioclases are framework silicates occurring in planetary crusts: on Earth they are the most common rock-forming minerals of igneous, metamorphic and sedimentary rocks, the most abundant minerals on the Moon and widespread in basaltic rocks on Mars and in asteroids like Vesta. Plagioclases are involved in several key reactions of petrologic interest, as igneous and metamorphic reactions. The investigation of their chemical composition is a key-point to understand the petrologic evolution of the parent rocks. In this work, we propose Raman spectroscopy as a procedure to gain chemical information from plagioclases, as already done in literature for garnets, amphiboles and serpentine group. CHARACTERIZATION OF PLAGIOCLASE SOLID SOLUTION BY RAMAN SPECTROSCOPY: A PROCEDURE FOR THE DETERMINATION OF THE CHEMICAL COMPOSITION Irene Aliatis 1*, Erica Lambruschi 1, Luciana Mantovani 1, Artur Benisek 2, Danilo Bersani 1, Michael A. Carpenter 3 ; Diego G. Gatta 4, Mario Tribaudino 1, Pier Paolo Lottici 1 1 Università di Parma, Dipartimento di Fisica e Scienze della Terra, Parco Area delle Scienze 7/A, 43124 Parma, Italy, irene.aliatis@difest.unipr.it 2 Universitaet Salzburg, Materialforschung und Physik, Hellbrunnerstr. 34, 5020 Salzburg, Austria 3 University of Cambridge, Department of Earth Sciences, Downing Street, Cambridge CB2 3EQ, UK 4 Università degli Studi di Milano, Dipartimento di Scienze della Terra, Via Botticelli 23, 20133 Milano, Italy The “Raman chemical compositions” methods has been made on the basis of Raman results found on a series of well characterized plagioclases, previously investigated by powder-XRD, TEM, IR spectroscopy and calorimetry. The samples consist of 20 homogeneous purified natural, low structural state plagioclases, showing the highest degree of Al,Si order possible for each composition. The chemical composition ranges from An 0 to An 100. Raman measurements have been performed with a Horiba Jobin-Yvon LabRAM apparatus in backscattering geometry, equipped with an Olympus BX40 confocal microscope and a He-Ne laser (λ = 632.8 nm). The difference in Raman wavenumber between the two major peaks (labelled as I a and I b ) of a series of 20 plagioclases is here proposed to determine their composition in terms of An content (mol%). 1 st METHOD2 nd METHOD The I a and I b differences vs. the An content: it is possible to calculate the composition only for the An-rich terms (An > 60%). The I a and I b differences vs. the intrinsic linewidth of the most intense Raman mode I a : in order to obtain compositional information for Ab-rich plagioclases too, we need to use this graph. Sample Chemical analysis Raman analysis (1 st method) Raman analysis (2 nd method) Juvinas91.289.386-96 Renazzo9996.689-96 V. Marsili PL3 86.284.272-78 V. Marsili PL1-2 44.7-40-60 Evolution of four modes with An content 290 I b 478 I a 508 578 Main Results An content Sample name Structural state An1Minas Gerais An1Amelia albite An20Hawk be2e2 An2797490e2e2 An3591315ce2e2 An40T-12-22ae2e2 An4667783e1e1 An4991413be1e1 An6011044ple1e1 An6067796be1e1 An65SKHHMe1e1 An68Lake Co. An7142771be1e1 An72Crystal Bay An78101377a An8621704a An8987975a An96115082a An98M. Somma An99Val Pasmeda Reference plagioclases Both methods have been tested on three different mineralogical case studies: 1)plagioclase crystals found in Juvinas eucrite meteorite (magenta) 2) anorthite crystals into a CAI inclusion within the Renazzo carbonaceous chondrite meteorite (cyan) 3)plagioclase crystals with heterogeneous chemical composition from the Marsili volcano (orange). Low albite structure