There is no "mechanism for how [ ... ] emergence occurs". Emergence
is the mechanism. This is even more true of qualia, which are definitionally subjective, and thus do not exist as phenomena in the world.
We could talk a bit about the mechanism behind the process where aggregating sufficient water molecules creates a liquid. But we can't talk at all about how that same process could ever be responsible for the experience of "wet", because the experience of wet is wholly subjective.
Similarly, even if we were to be able to fully describe the materialist processes taking place in a system that has qualia, nothing in the description can ever explain the experience of having experiences, beyond saying "well look here - see all this stuff going on? that's how qualia are possible", which is not tautological, but not a mechanism for qualia.
Speaking of "thinking" more generally is even worse than focusing on qualia. It's not hard to agree on what qualia are - that it is like something to be something, in Nagel's words - but agreeing on what would count as "thinking" and what wouldn't is not likely to see any agreement at all.
We could talk a bit about the mechanism behind the process where aggregating sufficient water molecules creates a liquid. But we can't talk at all about how that same process could ever be responsible for the experience of "wet", because the experience of wet is wholly subjective.
Similarly, even if we were to be able to fully describe the materialist processes taking place in a system that has qualia, nothing in the description can ever explain the experience of having experiences, beyond saying "well look here - see all this stuff going on? that's how qualia are possible", which is not tautological, but not a mechanism for qualia.
Speaking of "thinking" more generally is even worse than focusing on qualia. It's not hard to agree on what qualia are - that it is like something to be something, in Nagel's words - but agreeing on what would count as "thinking" and what wouldn't is not likely to see any agreement at all.