Lead partitions do not interact with each other, so you likely cannot do this within Marketo at least with the Duplicate Fields filter. A possibility that I have not tried is to
1. Create a Leads by email address report with all of the leads in one partition (Partition 1 Leads).
2, Create a smart list with all the leads in the second partition. (Partition 2 Leads)
3. Add the smart list as a custom column to the Partition 1 Leads report. Whereever there is an intersection, a '1' will be displayed in the custom column.
If this doesn't work, you can export both lists and use the Excel vlookup formula on their email addresses to identify matches.