Let's say hypothetically China blacklisted Australian iron ore....

Let's say hypothetically China blacklisted Australian iron ore. Chinese buyers would have to furiously compete for tight alternate supply from Brazil and wherever else, which would drive up the price in China.

Brazilian and other exporters would all rush to sell into this Chinese market. Why wouldn't they? Any Brazilian iron ore that would have gone to Japan, Korea, Europe, North America, India etc would be diverted to China. These rest-of-the-world buyers are then faced with a sudden loss of non-Australian supply and are forced to buy Australian.