Database Software

I have a table having only one column xmlcontent (xmltype). This table stores xml data of about 10GB size. I'm using extract value to move the data to staging tables.

How can I create index on xmltype column?
Create index indexname on table (column) doesn't seem to work.

Sample xmlstructure is given below
<Root>
<Type>Insert</Type>
<Date>2006-12-29</Date>
<Source>8</Source>
<id>data</id>
<key_flds>
<fld><id>Key1</id><val>C</val></fld>
<fld><id>Key2</id><val>429672</val></fld>
<fld><id>Key3</id><val>8</val></fld>
</key_flds>
</Root>

I need to do extract value on all tags and move them to corresponding relational tables.