Is it true all aust exporters IO BHP RIO ect all contracts...

Is it true all aust exporters IO BHP RIO ect all contracts written in US $...???? IF so do they now get 3o% plus increase in their IO price ???? why are these super profitable cos @ leading Aust gold miners being sold off ???? or is this just panic selling from overseas???Both ceos BHP & RIO say CHINA will continue to plough ahead.The other question the chineese purchased a major share in RIO @ 140 something dollars per share @ these prices wouldnt you think they will enter the market @ snavell both RIO & BHP shares ??????