Carbine Resources (ASX:CRB) continues to advance its gold-copper tailings retreatment project at the historic Mt. Morgan gold mine in Central Queensland, Australia, with the release of a scoping study suggesting very positive economics. The study, released last week, is based upon a 1-million-tonne-per-year operation and points to annual production of some 36,000 ounces of gold, 850 tonnes of copper and 230,000 tonnes of pyrite over an eight-year mine life. It also posits a start-up capital cost of AU$83 million and an all-in sustaining cost of US$393 per ounce of gold, net of by-product equivalents, potentially placing the project in the bottom quartile of the global gold cost curve. Furthermore, the study is based upon the existing small JORC resource that has been defined over the tailings dams and does not take into account the additional tailings storage areas that have not been drilled to resource level and could yet increase that resource several fold. A long history The original Mt. Morgan mine operated for almost 100 years, from 1888 to 1980, over which time 50 million tonnes of ore were processed, producing 8.4 million ounces of gold, 1.12 million ounces of silver and 400,000 tonnes of copper. Substantial tailings were subsequently processed for another 10 years, before the operation closed in 1991. Carbine acquired an option over the project in early 2014 from Norton Gold Fields (ASX:NGF). It includes the historical mine, tailings and the nearby Kundana plant, and is subject to a period of due diligence, which is to be devoted largely to developing greater confidence in the processing stream for the recovery of the various contained metals. During the first phase of tailings retreatment up to 1991, gold recoveries from the tailings ponds were reported at only 51 percent. Norton improved on that as it moved the project through the feasibility process, claiming 65 percent recovery and an estimated cash cost of between US$600 and $650 in 2010. Problems, however, persisted related to high cyanide consumption and the containment of acid-producing materials from the high-sulfur ore.