Cracked engine block?

I've got hold of a service manual, looks like it its the "oil pan upper":

Attachment 47488

Agreed, it does look like alloy now that i've leaned it up. I don't know much about the ZD engines, so not entirely sure.

What worrying me is that the removal steps state 'Separate the transmission', not sure if this just means undo the bolts between the oil pan and the tranny, or whether the whole things needs to be separated from the engine. The manual isn't that clear.

Attachment 47490

I'm getting my garage to have a look at it Saturday morning, so hopefully then can confirm how serious this is.

Good news, garage thinks that is a casting line. Keep an eye on it is the advice, so hopefully I can stop worrying about it :)