Mt Todd Gold Project - Gold Resource Update

Abstract

This is a NI 43-101 Technical Report to the TSX. Tetra Tech, Inc. ('Tt') was commissioned by Vista Gold Corp. ('Vista') in November 2007 to prepare an updated Canadian National Instrument 43-101 (NI43-101) compliant Technical Report on the Mt Todd Gold Project (the 'Project') located in the Northern Territory, ('NT') Australia. On March 1, 2006, Vista purchased the Mt Todd property, and the acquisition was completed on June 16, 2006, when the mineral leases transferred to Vista and funds were released from escrow. An initial NI43-101 Technical Report was completed on June 26, 2006, a Preliminary Economic Assessment report was completed on December 29, 2007, and this report is an update of the June 26, 2006 Technical Report and is based on additional exploration drilling completed by Vista during 2007. The Mt Todd property contains a number of known occurrences of gold, which have been explored and/or exploited to various degrees. The largest and best-known deposits are the Batman and Quigleys Deposits. Both of these have had historic mining, with Batman having the most production and exploration completed. The Batman Deposit shares some characteristics with intrusion-related gold systems, especially in terms of the association of gold with bismuth and reduced ore mineralogies. This makes the deposit unique in the Pine Creek area. The mineralization within the Batman Deposit is directly related to the intensity of the north south trending quartz sulfide veining. The lithological units impact on the orientation and intensity of mineralization. Sulfide minerals associated with the gold mineralization are pyrite, pyrrhotite and lesser amounts of chalcopyrite, bismuthinite and arsenopyrite. Galena and sphalerite are also present but appear to be post-gold mineralization and are related to calcite veining, bedding and the east-west trending faults and joints. At the present time, resources have only been estimated for the Batman Deposit. Tt created three-dimensional computerized geologic and grade models of the Batman Deposit. While the deposit model also contains the Quigleys Deposit, no geologic resource estimate has been made for this deposit at the present time. The geologic model of the Batman Deposit was created by General Gold Corporation ('GGC') and audited by Tt. The geologic model was constructed by creating three-dimensional wireframes of the main geologic units, oxidation types, and mineralizing controls and superimposing them on each other to create an overall numeric code that details all of the input parameters. GGC created the model based on the prior work of others, recommendations of other consultants, and GGC's own experience. It is Tt's opinion that the GGC's geologic model accurately portrays the geologic environment of the Batman Deposit. Tt used the geologic model to guide the statistical and geostatistical analysis of the gold assay data. The analysis of the gold assays further confirmed the geologic divisions made by GGC in the geologic model. Gold grades were estimated into the individual blocks of the model by ordinary, whole-block kriging. The rock model was then assigned a tonnage factor based on the oxidation state (i.e. oxidized, transition, primary). The tonnage factors were based on a number of tests from the core and, in Tt's opinion, are representative of the various rock units, and are acceptable for estimation of the in-place geologic resources. The estimated gold resources were classified into measured, indicated, and inferred categories. The classification was accomplished by a combination of kriging variance, number of points used in the estimate, and number of sectors used.