Mineralogical, chemical and difratometrical analysis of rosenbuschite group minerals (sorosilicates) from South-American agpaític rocks

• Grant number: 11/21284-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2012
• End date: December 31, 2012
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Gaston Eduardo Enrich Rojas
• Grantee: Renata Panseri Rodrigues
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

This research project aims the study minerals of the rosenbuschite group, which are rare titanium and zirconium-bearing sorosilicates that may occur in agpaitic alkaline rocks. Analytical procedures will combine optical microscopy, scanning electron microscopy, electron microprobe (major and minor elements), and X-ray diffraction. The crystal-chemical study will emphasize the cationic distribution, in order to identify compositional variations, substitution mechanisms, and their extensions. The textural and chemical observations are relevant to further petrological studies on crystallization, magmatic and hydrothermal history, as well as the genesis and magmatic evolution of accessory minerals. Selected samples from Cerro Boggiani (Paraguay) and Búzios Island (São Paulo coast) alkaline massifs were selected for the study. Both are composed primarily of massive syenite and nepheline syenite, where rosenbuschite group minerals were previously described. It is worth mentioning that this project is linked to a research project on "Compositional variation in Zr-, Nb-, and Ti-sorosilicates and cyclosilicates from agpaitic alkaline rocks and its petrological significance" (FAPESP, proc. 2010/20476-1).(AU)