ゆく used in auxiliary sense - instead of いく?

Question

I'm reading a novel 「キッチン」by 吉本ばなな at the moment and I noticed that she uses ゆく in some places as an auxiliary verb to signify the action progression from here or from now (if my understanding is correct). I can quote two examples:

雨に覆われた夜景が闇ににじんでゆく大きなガラス、に映る自分と目が合う。

[...] はるかに淡い空に薄い雲がゆっくりと流れてゆく。

So far in my study of Japanese I have encountered いく used this way. Can ゆく be used the same way? Will those sentences have the same meaning if ゆく was replaced by いく? Is ゆく commonly used this way in modern Japanese?

Answer 1

I agree with l'électeur that it is quite common to pronounce 言{い}う as 言{ゆ}う for example...

そんなこと言{ゆ}った気{き}がしたな～

However going back to ゆく

行{い}く although often interchangeably pronounced 行{ゆ}く when spoken, is also written that way commonly when referring to things like destination

東京{とうきょう}行{ゆ}き電車{でんしゃ}まもなく発車{はっしゃ}いたします

In more detail (and taken from a Japanese Q and A site) http://oshiete.goo.ne.jp/qa/1637122.html - 日本語

『ゆく』は、時の経過を表し、『いく』は、人、物の移動を表す、と思いますが。

The ゆく reading represents the passage of time, wheras いく is used when referring to a person, representing the movement of goods.

Answer 2

Oftentimes I come across this particular way of adjusting/mutating iku to yuku when talking about background/weather events.

It would not be wrong to put "iku" in its stead, but "yuku" is almost like a "and so the rug goes on, being pulled out from under our feet" as opposed to "there he goes pulling the rug out"

One would also say "yuku" for the transmigration of one's spirit upon death.

It's like a "graceful drawing out" or "graceful drawing/dawning upon," where 'yuku' dances. Iku would just not have the same effect.