Quantity vs. Quality

I'm teaching a novel writing class and we are using the No Plot? No Problem! philosophy of shooting for the word count, quality be damned. It's also a kind of variation on Anne Lamott's idea of Shitty First Drafts. Just get it down, you can fix/revise/cut it later.
However.
However, yesterday as I speed-typed my way to 20,000 words (even I, the teacher, am about 4,000 words behind), my novel took a turn for the weird. And by weird, I mean paranormal, maybe, but it could just be first-person delusion. Or, it could have been a weird coincidence. But, my question to you, oh wise and worldly readers, is: do I go with this weird turn? I'm afraid it might mean that when I reach the 50,000 word mark (the goal), that I will have to cut the last half the book and rewrite that.
Or, I could just say, okay, that's weird, but I can rewrite that little chunk later, and go on with the book as if that weird/paranormal/delusional part never happened. (Except I got a good section of description and I could go back and revise it so it's not so important in the overall plot of the book).
My normal philosophy of writing would be to go with it and see where it takes me. I'm worried, however, that this weird turn will make what I am trying to do (an artsy/noir/mystery type thing) into something else (a paranormal mystery/young adult series). Not that the something else is BAD (though it could be terrible) it's just not what I set out to do.
What to do? What to do?
Please help. For now, I'm stuck.