March 13 (Reuters) - Guyana's government has cancelled

the Frontera and CGX Energy ( CGXEF ) joint venture's

prospecting license for the Corentyne block, the companies said

on Thursday.

In February, the South American nation gave a 30-day notice

to CGX and Frontera for cancellation of the license.

The Corentyne block was seen as a key effort to diversify

Guyana's oil industry, currently dominated by a consortium led

by Exxon Mobil ( XOM ).

The Frontera joint venture said it was informed of the

licence cancellation in a letter from the government. The

companies did not provide any further details, but disputed the

cancellation.