Acquisition

Antofagasta PLC
23 December 2005

                                ANTOFAGASTA PLC





                                                    For immediate release

   Antofagasta plc to enter into a joint venture with Tethyan Copper Company
       Limited in relation to the Reko Diq copper-gold region in Pakistan

LONDON - 23 December 2005: Antofagasta plc ('Antofagasta') is pleased to
announce that it has signed a binding Heads of Agreement ('HoA') with Tethyan
Copper Company Limited ('Tethyan'), a company listed on the Australian Stock
Exchange, involving the acquisition by Antofagasta of a 50% equity interest in
Tethyan's mineral interests in Pakistan and the concurrent subscription for a
19.95% shareholding in Tethyan.  Antofagasta, together with Tethyan, have also
entered into a deed of termination with BHP Billiton entities ('BHP Billiton')
whereby BHP Billiton's rights to claw-back a material interest in certain of
Tethyan's mineral interests ('Claw-back Right') will be extinguished ('BHP
Billiton Termination Deed').

Tethyan's principal assets are a 75% interest in the exploration licence
encompassing the highly prospective Chagai Hills region of North West Pakistan
known as Reko Diq, which includes the Tanjeel Mineral Resource and the Western
Porphyries, and a 100% interest in certain other licences in the region. This
mining district hosts significant copper-gold porphyry deposits as part of an
extended copper-gold belt.  Tethyan has reported total indicated and inferred
mineral resource estimates at these properties of 1,213 million tonnes with a
copper grade of 0.58% and a gold grade of 0.28 grams per tonne.  The resource
estimates include probable reserves at the Tanjeel Mineral Resource of 128.8
million tonnes with a copper grade of 0.7%. Reserve and resource estimates have
been reported by Tethyan to JORC standards.

Under the HoA, Antofagasta has agreed to:

•       acquire a 50% equity interest in Tethyan's mineral interests in Pakistan
through the subscription for US$37.5 million of newly issued equity capital into
a joint venture vehicle to be established;

•       commit to funding further exploration and development expenditure and
related joint venture costs of up to US$75 million.  In the event that
Antofagasta spends less than this amount, its 50% equity interest will be
reduced on a pro-rata basis; and

•       subscribe for 33 million new ordinary shares in Tethyan for a total
subscription price of US$20.5 million, equating to 19.95% of Tethyan's enlarged
issued share capital (17.3% on a fully diluted basis).

Under the BHP Billiton Termination Deed, Tethyan have agreed to pay BHP Billiton
a compensation amount of US$50M in consideration for terminating the Claw-Back
Right and other rights under the Alliance Agreement between BHP Billiton and
Tethyan, of which US$45M is payable at closing and US$5M is payable in four
equal instalments over the four years following closing.

It is expected that Antofagasta's total financial commitment under this
transaction, including the exploration and development expenditure commitment
under the HoA, will amount to US$133 million.  Implementation of the proposed
transactions under the HoA and the BHP Billiton Termination Deed are subject to
certain conditions precedent including due diligence, Tethyan shareholder
approval, necessary Pakistan and Balochistan authority approvals and receipt of
all other necessary regulatory and third party approvals.

Tethyan is currently subject to an unsolicited takeover offer from Skafell Pty
Ltd ('Skafell'), a subsidiary of Crosby Capital Partners Inc. and IB Daiwa
Corporation.  The Tethyan Board has unanimously recommended that its
shareholders reject the Skafell takeover offer and approve the proposed
transaction with Antofagasta, in the absence of a superior offer for Tethyan
emerging.  Tethyan has agreed to pay Antofagasta a break fee in certain
circumstances, including where the Tethyan Board withdraws its recommendation
for the proposed transaction with Antofagasta.

Marcelo Awad, CEO of Antofagasta Minerals S.A., stated, 'Our agreement with
Tethyan Copper Company provides Antofagasta with a window into a very
prospective mining region and represents a strategic investment opportunity for
us.  A partnership with Tethyan will allow Antofagasta to apply its mining and
development skills and its experience in large-scale projects, to evaluate the
mineral resources at Reko Diq and ensure that they are developed to their full
potential to the mutual benefit of the shareholders of both Antofagasta and
Tethyan.  Whilst Latin America, and Chile in particular, will continue to be
Antofagasta's primary region of focus, this investment is consistent with our
long term growth strategy and subject to our rigorous investment and risk
evaluation criteria.  Antofagasta continues to look at opportunities globally to
secure rights to world-class mining assets to enhance its overall growth
profile.'



The agreements referred to above were signed after the last time at which an
announcement of the transaction could have been made by Tethyan through the
Australian Stock Exchange. A detailed announcement is expected to be made by
Tethyan at the opening of trading on the Australian Stock Exchange on Wednesday
28 December 2005.

Antofagasta plc is a Chilean-based mining group listed on the London Stock
Exchange and is a constituent of the FTSE-100 index.  Its principal mining
assets include the Los Pelambres, El Tesoro and Michilla mines and the Esperanza
copper project.  In addition to copper mining, Antofagasta's interests include
rail and road transport operations and water distribution.



Rothschild is advising Antofagasta in relation to this transaction.




Enquiries - London                                                            Enquiries - Santiago
Antofagasta plc                                                          Antofagasta Minerals S.A.

Tel: [phone]                                                           Tel: [phone]

www.antofagasta.co.uk

                                                                                      Marcelo Awad

Desmond O'Conor                                                          Email: [e-mail]

Email: [e-mail]

                                                                                Tel: [phone]

Issued by
Bankside Consultants                                                              Alejandro Rivera
020 7367 8888                                                          Email: [e-mail]



Keith Irons
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Email: [e-mail]



Oliver Winters
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