Mineralogy of the Ash Mountain Sn-bearing skarn, Tuya Range, northern British Columbia, Canada

摘要

The Ash Mountain Sn-bearing skarn, located in the Tuya Range of the Cassiar Mountains in northern British Columbia (59 degrees 17'50 '' N, 13 degrees 31'040 '' W), was investigated in order to provide the first modern, comprehensive characterization of its mineralogy and zoning and to identify the main skarn-forming processes. The Ash Mountain skarn is unusual with respect to other Sn-bearing skarns because the main Sn-bearing minerals are malayaite and andradite (with 2.33 wt.% SnO2), and no cassiterite has been found to date. The associated intrusive body-the Parallel Creek granite-is a highly fractionated, felsic, Atype, biotite granite that was generated in a within-plate setting. The biotite in the granite is Al-rich annite with elevated Ti (up to 2.77 wt.% TiO2), F (up to 2.04 wt.% F), and Cl (up to 0.33 wt.% Cl); annite in an associated aplite dike contains up to 0.47 wt.% Cl. High F and Cl in annite indicate a high amount of fluxing components and could be used as an indicator of mineralized granites.