Framing the future of zinc concentrate

Over the years, there has been a trend to increased trading in the spot market at the expense of frame contract business. This can be linked directly to China that started buying concentrate from the rest-of-the-world (ROW) in the early 2000s. This begs three questions: - Will the lower-treatment charge spot business continue to expand at the expense of higher-treatment charge frame contracts? - Conversely, could the tonnage of concentrate under frame contracts be given a boost from the expansion of zinc smelting? - Trafigura and Glencore have transformed from trading companies into the second and third largest zinc smelting companies in the world. How has this changed their view of frame versus spot buying and selling of concentrate?