| Abstract:Gejiu tin deposit is a world-class Sn-Cu polymetallic deposit related to the high differentiation granite in the Late Cretaceous, and its mineral origin and fluid evolution process have always been the focus and difficulty of research. Tourmaline is widely developed in carbonate rock, granite and skarn in Gejiu area, but the relationship between tourmaline and mineralization is not clear. In this paper, systematic petrographic observation and electron probe (EPMA), LA-ICP-MS analysis of trace elements and boron isotopes of different types of tourmaline have been carried out. The results show that all tourmalines belong to basic tourmaline, TurⅠ, TurⅡ, TurⅣ are of hydrothermal origin, TurⅢ are of magmatic origin. Compared with hydrothermal tourmaline, magmatic tourmaline has lower Mg, Ca and other elements, and the high Sr content of TurⅠ tourmaline indicates that it is contaminated by surrounding rock. The variation of trace elements in the turmaline shows that Sn is gradually enriched in the magma and precipitated in the porphyritic granite and contact skarn with the increasing degree of magmatic differentiation from porphyritic granite to equite-grained granite. The different types of tourmalines have uniform δ11B values (?15.2‰~?12.8‰), which are consistent with the composition range of granite, indicating that the ore-forming materials all come from granitic magma. |
