I think that at 41k per kilo one tonne of gold is worth $41m. 1300 tonnes of gold is therefore worth a bit more than $51bn, which is a lot, but approximately 1 year of the UK's defence budget, so in the scale of things not really all that much. Now, this would mean that (given that Germany is a big economy) there would be what... 20 times that amount of gold available to back a gold currency - so about $1trn. I think…
If China really created gold-backed currency then gold price would skyrocket, increasing at lest 6 times (that's how much inflation we had since 1971, when the gold standard was abandoned)