Abstract
Tourmaline from the St. Byron lobe of the Land’s End granite, SW England, was assessed by macroscopic, optical and quantitative microanalytical methods. In total, seven types of tourmaline were distinguished. The seven types reflect different crystallisation environments and stages in the magmatic-hydrothermal transition. Types 1-3 are interpreted to represent a gradual transition from tourmaline crystallising from a silicate melt to precipitation from magmatic aqueous fluids. Types 5-7 crystallised at subsolidus conditions from a different fluid generation than types 1-3. These fluids may be magmatic or mixed with other fluids (e.g., meteoric or formation waters). The Sn-mineralisation in the area is mostly related to the latter fluid generation, and the mineralising potential is reflected by the tourmaline composition.
Highlights
Tourmaline is the most common borosilicate mineral in the crust
The Sn-mineralisation in the area is mostly related to the latter fluid generation, and the mineralising potential is reflected by the tourmaline composition
Within the Cornubian Batholith of SW England, which has served as a field laboratory in this study, evidence of boron-rich fluids migrating through fracture systems in the crystallised granite and country rock can be observed as black, tourmaline-rich veins
Summary
Tourmaline is the most common borosilicate mineral in the crust. It is found in magmatic, metamorphic, and sedimentary rocks, but is perhaps best known for the striking, museum-grade crystals found in South America and Central Africa. It has the general formula XY3Z6T6O18BO3V3W, where the X-site is occupied by Na, K, Ca, Pb, and vacancies; the Y-site by Fe2+, Mg, Mn, Li, Ti, Al, Fe3+, and Zn; the Z-site by Al, Cr, Fe3+, Mg, and Fe2+; the T-site by Si, B, and Al; the B-site by B; the V-site by OH and O; and the W-site by OH, F, and O.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: IOP Conference Series: Materials Science and Engineering
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.