The sentence
The other force is a gush of private-equity finance, much of it originating in America and landing in Europe.
Is fine and understandable
The other force is a gush of private-equity finance, much of which originating in America and landing in Europe.
is incorrect, the correct version is
The other force is a gush of private-equity finance, much of which originates in America and lands in Europe.
If you remove "much of" the first sentence is still fine, so long as you remove "it"
The other force is a gush of private-equity finance, originating in America and landing in Europe.
You don't need "much of" because it is grammatically possible for all finance to originate in America and land in Europe. You can be more specific and say only "much of" the finance originates in America and lands in europe, but either makes for a correct sentence.
The other force is a gush of private-equity finance, it originating in America and landing in Europe.
Is wrong. The "it" is jarring, since we already have the subject of the sentence, "private-equity finance", and the "it" is unnecessary, and breaks the flow of the sentence to the point where you would want to make it into two sentences.
The other force is a gush of private-equity finance. It originates in America and lands in Europe
Although be warned using "it" is dangerous, as "it" is such a general pronoun you have to be 100% clear what "it" is referring to.
