Constraints on metallogenic temperature and mineralization style from reflection color of sphalerite

Abstract

The relationship between the color of sphalerite and trace elements has aroused the interest of researchers since a long time, but most of the study is still in the qualitative stage. In this contribution, we made attempt to reveal the relationship between the reflection color and its trace element, in order to discuss the genetic significance of various reflection colors of sphalerite through the quantitative study of reflection color of sphalerite. Based on LA-ICP-MS analysis and microspectrophotometer analysis of sphalerite samples in different types of deposits, the elements with significant correlation with the reflection color index were found and analyzed by factor analysis. Different genetic types of sphalerites have different color index, The average reflection color indices of each type sample are as follows, sphalerite from Mengya’a deposit: λd = 477.3 nm, Pe = 0.046, Rvis = 17.23%; sphalerite from Zhaxikang deposit: λd = 477.2 nm, Pe = 0.043, Rvis = 16.70%; sphalerite from Nanmushu deposit: λd = 476.4 nm, Pe = 0.038, Rvis = 16.55%. The reflection color index of sphalerite is correlated with the content of Mn, Fe, Ga, Ge, Ag, Cd, In, Tl, Pb. The results of factor analysis indicate that sphalerite with high reflectivity is more abundant in Fe, Mn and In, while the sphalerite with low reflectivity is more abundant in Ge, Tl, Pb and Ag. Furthermore, the reflection color index of sphalerite can be used to distinguish the genetic type of deposits. Based on an obvious linear relationship between the reflection color index of sphalerite and its mineralization temperature, we propose a new empirical equation: T(°C) = 61.4*Rvis + 1.1*λd + 6000*Pe-1533 which can be used as a geological thermometer.