ASSIGNMENT AGREEMENT

      This Agreement dated as of the 10th day of November, 2005

BETWEEN:

            GOLDSTRIKE INC.
            Incorporated under the laws of the State of Nevada
            (herein called "Goldstrike")

                                     - AND -

            GRAN TIERRA GOLDSTRIKE INC.
            Incorporated under the laws of the Province of Alberta
            (herein called "ExchangeCo")

WHEREAS:

A.    Goldstrike  is a  party  to  a  share  purchase  agreement  (the  "Assumed
      Contract")  dated  November 10, 2005 among Gran Tierra Energy Inc.  ("Gran
      Tierra"),  the vendors  named in the  Assumed  Contract,  as vendors,  and
      Goldstrike,  as  purchaser,  pursuant  to which  Goldstrike  has agreed to
      purchase certain securities of Gran Tierra Energy Inc; and

B.    Goldstrike wishes to assign and ExchangeCo  wishes to assume  Goldstrike's
      rights and obligations under the Assumed Contract  effective  November 10,
      2005 (the "Effective Date").

      WITNESSES THAT in consideration of the mutual covenants  contained in this
Agreement and other good and valuable consideration (the receipt and sufficiency
of which is acknowledged by each of the parties), the parties covenant and agree
as follows:

1.    ASSIGNMENT OF ASSUMED CONTRACT

      1.1.  Goldstrike hereby absolutely  assigns,  transfers and sets over unto
            ExchangeCo  as and from the  Effective  Date,  with  respect  to the
            Assumed Contract:

            1.1.1 all the rights, title and interest of Goldstrike in, to, under
                  and in respect of the Assumed Contract;

            1.1.2 the benefit of all covenants and agreements and guarantees and
                  indentures  (the   "Covenants")  in  respect  of  the  Assumed
                  Contract;

            with full power and  authority to demand or sue for  performance  of
            the  Covenants,  in the  name of  Goldstrike,  but at the  cost  and
            expense of ExchangeCo.

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                                      -2-


      1.2.  ExchangeCo   hereby  assumes  the  obligations  and  liabilities  of
            Goldstrike  under the Assumed  Contract  arising or to be  performed
            from and after the Effective Date,  including but not limited to all
            covenants  of  confidentiality,  and  agrees to  indemnify  and save
            harmless  Goldstrike  with respect to all Damages (as defined in the
            Assumed  Contract)  arising from or in connection with, or resulting
            from, any breach or  non-observance  by ExchangeCo or those for whom
            it is  responsible  in law, from and after the Effective Date of any
            of  ExchangeCo's  obligations  and  liabilities  under  the  Assumed
            Contract.

      1.3.  Without limiting paragraph 1.2,  ExchangeCo confirms and agrees that
            from the Effective Date it shall be liable as a principal and not as
            a surety in respect of the representations,  warranties,  covenants,
            indemnities and agreements of Goldstrike as contained in the Assumed
            Contract.

2.    GOLDSTRIKE'S COVENANTS

      2.1.  Goldstrike covenants and agrees:

            2.1.1 to pay all costs in respect of  obligations  which arise prior
                  to  the  Effective  Date  which  are  the   responsibility  of
                  Goldstrike under the Assumed Contract; and

            2.1.2 that it will remain  responsible to ExchangeCo for liabilities
                  for obligations  under the Assumed  Contract  arising or to be
                  performed   prior  to  the  Effective  Date  and  defaults  of
                  Goldstrike  under the  Assumed  Contract  either  incurred  or
                  committed  prior to the Effective Date and agrees to indemnify
                  and save  harmless  ExchangeCo  with  respect  to all  Damages
                  arising from or in  connection  with, or resulting  from,  any
                  breach or non-observance by Goldstrike or those for whom it is
                  responsible  in law,  prior to the  Effective  Date, of any of
                  Goldstrike's  obligations  and  liabilities  under the Assumed
                  Contract.

3.    MISCELLANEOUS

      3.1.  In this  Agreement,  where the context so requires,  the singular of
            any word includes the plural, and vice versa, the use of any term is
            generally  applicable  to any gender  and,  where  applicable,  to a
            corporation.

      3.2.  The  headings in this  Agreement  are inserted  for  convenience  of
            reference only and shall not constitute a part hereof and are not to
            be considered in the interpretation hereof.

      3.3.  Each of the parties hereto shall at all times after the date of this
            Agreement  execute and do all such  further  deeds,  acts things and
            assurances as may be reasonably requisite to carry out the intent of
            this Agreement.

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      3.4.  This  Agreement will enure to the benefit of and be binding upon the
            parties hereto and their respective successors and assigns.

      3.5.  This Agreement shall be governed by and construed in accordance with
            the  laws  of the  Province  of  Alberta  and  the  laws  of  Canada
            applicable  therein  and  shall be  treated  in all  respects  as an
            Alberta contract.

      3.6.  This  Agreement  may not be  modified  or amended  except in writing
            signed by the parties hereto.

      3.7.  The  provisions  of this  Agreement  shall  survive  the Closing (as
            defined in the Assumed Contract).

      3.8.  This Agreement may be executed in any number of  counterparts,  each
            of which shall be deemed an original. This Agreement may be executed
            and delivered by facsimile transmission.

      IN WITNESS OF WHICH this  Agreement  has been  executed  as of the day and
year first above written.

GOLDSTRIKE INC.


Per:
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     Name:
     Title:

GRAN TIERRA GOLDSTRIKE INC.


Per:
     ---------------------------------------
     Name:
     Title:

ACCEPTED AND AGREED TO:

GRAN TIERRA ENERGY INC.


Per:
     ---------------------------------------
     Name:
     Title: