The phrase 'which is cause' is correct and usable in written English.
You can use it to state a cause or reason for something. For example, "He failed the test, which is cause for concern."
None of which is cause for total panic.
This fact proved the tilting of octahedra which is cause of superlattice.
But it is not clear which is cause and which effect.
The team that knocked them out was Atlético Madrid, which is cause for optimism at the Calderón.
Higher government spending tends to be associated with slower growth, but which is cause and which is effect?
It's available now, which is cause for rejoicing, but the proximate cause of saying so is lamentable: Dixon died on Wednesday, at the age of eighty-four.
Initially, avian cholera, which is caused by bacteria, was suspected.
There's now an influx of crystal meth, which is causing people to be extremely violent.
They resemble leaf spots due to late blight, which is caused by a related pathogen.
Chickenpox, which is caused by the varicella-zoster virus, has no cure.
More heat is being absorbed, which is causing more sea ice to melt, and so on.
