Toronto Geological Discussion Group
CASTELO DE SONHOS: DE-RISKING A GOLD PALEO-PLACER USING TOOLS AND METHODS FROM THE PETROLEUM INDUSTRY
Mohan Srivastava, Vice President, TriStar Gold
Castelo de Sonhos is a paleo-placer gold deposit in Pará State, Brazil, that TriStar Gold is advancing toward a preliminary economic assessment (PEA) this year. In 2016, the project’s risk and its potential were quantified using a geostatistical approach not previously presented in National Instrument 43-101 technical reports. All available data from several exploration programs were integrated with recent advances in paleo plate reconstructions, in modeling fluvio-deltaic systems, in numerical simulation, and in data mining. The innovative integration of data and geology made it possible to quantify the exploration target in the manner required by 43-101: as a range of possible tonnages and grades. Although preliminary resource estimates for the project had already been reported, defining the exploration target had the benefit of establishing a correct understanding of the scale of the project. This quantitative risk assessment not only improves scoping studies, but has also made it possible to finance a project once regarded as being too small by many mining companies.
This TGDG talk will discuss the project’s important milestones during the past year, including the ground-truthing of the exploration target’s conceptual model using widely-spaced step-out holes to extend the known mineralized strike length by more than two kilometers. It will also show how probabilistic methods have continued to assist project development, particularly in the “what-if” studies TriStar has used to build confidence that the PEA will be properly scaled in the sense that it will be based on resources sufficient to allow for proper assessment of eventual production rate and life-of-mine.
The talk concludes with discussion of current field work that uses technologies common in the petroleum industry, petrophysics and optical televiewer, to supplement reverse-circulation drilling and to assist with the development of a detailed understanding of the stratigraphic controls on gold mineralization.
Speaker: Mohan Srivastava
R. Mohan (“Mo”) Srivastava is Vice President of TriStar Gold Inc., and leads their technical work on project development. Mo has a B.Sc. in Earth Sciences from MIT, where he specialized in sedimentary geology, and an M.Sc. in Geostatistics from Stanford University. As a consultant in resource estimation for three decades, he has provided advice and assistance to both the mining and petroleum industries. He has contributed to many 43-101 technical reports, where he has often introduced probabilistic methods for quantifying uncertainty and assessing risk in natural resource evaluation. He is a co-author of the widely-used textbook An Introduction to Applied Geostatistics, and of many technical papers and book chapters on the theory and practice of geostatistics. In 2016, Mo won the APGO’s Award of Merit for lifetime contributions to geosciences.
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