"If you look at Marx's work on finance, he refers to it as a form of primitive accumulation."
But when I search my e-book of Marx's Capital volume three (in which he analyses finance) each and every occurence of the phrase 'primitive accumulation' is followed with the reference: "(Buch I, Kap. XXIV [English edition: Part VIII.-Ed.])" In other words, primitive accumulation belongs in the historical account of the emergence of capitalism.
First reference is in chapter five, p 326, where Marx says that the separation of the labourer from the means of subsistence is present from the moment of primitive accumulation.
The second is in chapter thirty seven, p 830, when he makes the same point.
The third is in Chapter 51, p 1177 where he makes the same point again, though with reference to rent and land ownership.
All references Karl Marx, Capital, Volume Three, The Process of Capitalist Production as a Whole, Electronic Book Company, London, 1998