A potential copper porphyry system was first identified at Florence in the early 1960s. By the late 1970s, significant drilling and metallurgical testwork had been completed by Conoco.
Conoco’s conceptual studies included both the oxide and sulfide portions of the deposit, and encompassed an oxide open pit mine, with vat leaching and solvent extraction-electrowinning (SX-EW) treatment of oxide mineralization, followed by extraction of the sulfide material and treatment in a conventional concentrator, with smelting and refining. However, the low price of copper and overall large capital investment precluded development.
Magma Copper Company acquired the property in 1992 and completed a prefeasibility study in 1995. The study focused on identifying the most appropriate mining method for developing the oxide portion of the deposit, which included (1) open pit mining followed by heap leaching, and (2) in-situ copper recovery followed by SX-EW treatment. The latter appeared to be the most economical option; however, low copper prices prevented development.
BHP acquired Magma in 1996 and created BHP Copper, Inc. which advanced the project to the fully permitted stage for ISCR production. In 1998, BHP initiated, but did not complete, a multi-month, field-optimization in-situ recovery test to gather copper-extraction and other technical data.
Curis acquired the Florence Copper project, including project permits, in February 2010. The project obtained all major environmental permits under BHP in the late 1990s, and Florence Copper is currently in the process of amending and updating these permits. In 2010, the Florence Copper project , was acquired by Curis Resources.
In November 2014, Taseko acquired Curis and in turn acquired 100% ownership in Florence Copper.
The Florence Copper deposit formed approximately 62 million years ago when numerous dike swarms of Laramide granodiorite porphyry intruded Precambrian quartz monzonite near Poston Butte. Hydrothermal solutions associated with the intrusive dikes altered the host rock and deposited copper and iron sulfide minerals as disseminations and thin veinlets in the strongly faulted and fractured rocks.
The deposit was subjected to mid-Tertiary Basin and Range faulting and subsequent erosion, burying the entire deposit to a depth of approximately 375 feet. During the latter period, calcareous silty mud and clay layers were deposited in shallow basins that extended over the region. A 20-40 foot thick clay layer lies 60 to 100 feet above the bedrock and acts as an aquitard, preventing groundwater in aquifers above and below the clay layer from mixing. Mineralization in the oxide portion of the deposit consists primarily of chrysocolla with lesser other secondary copper minerals. Most of the copper in chrysocolla occurs in veins or as fracture fillings. The thickness of the oxidized zone ranges from 100 to 1,000 feet with an average thickness of 400 feet.
Underlying the oxide mineralization are sulfide (hypogene) and enriched (supergene) zones. In most instances, the transition from the oxides to the sulfide zone is quite abrupt.
The oxide mineralogy, fracturing, abrupt change from the oxide to sulfide zone as well as the presence of an overlying clay layer or aquitard, make the Florence Copper deposit highly amenable to in-situ copper recovery.
In 2013, a Prefeasibility Study for the Florence Copper Project was announced, including:
- Initial capital cost of US $120 million
- Payback of capital 2.6 years (pre-tax)
- Cash operating cost of US$0.80/ pound
- Total estimated operating cost of US $1.11/ pound
- Average annual copper production of 75 million pounds
- Long mine life of 25 years
1 Average grade 0.358% TCu at a cut-off grade of 0.05% TCu March 2013 Florence Copper Prefeasibility Study Technical Report, Independent Qualified Persons are Richard Zimmerman, RM-SME, M3 Engineering & Technology Corp.; Michael Young, RM-SME, Haley & Aldrich; Corolla Hoag, CPG, RM-SME, SRK Consulting, Dr. Terence McNulty, PE, TP McNulty and Associates; Dennis Tucker, PE, ARCADIS, and Richard Frechette, PE, Knight Piesold.
Net Present Value (NPV Analysis)
|Copper Price US$/lb||Pre-tax NPV/IRR||Post-tax NPV/IRR|
|$3.00||US $850 Million / 38%||US $585 Million / 31%|
In 2012, an economic benefit study was completed by Arizona State University’s prestigious L. William Seidman Research Institute showing significant socio-economic benefits for Arizona, Pinal County, and the Town of Florence. An update to chapter 5 of the original study was completed in 2013 and is based on the project’s Pre-Feasibility Study filed with SEDAR on March 28, 2013.
The updated socio-economic data prepared by the L. William Seidman Research Institute at Arizona State University shows:
Over the 30 year life of the project, Florence Copper represents:
- $3.3 billion in economic activity for the state of Arizona
- $2.1 billion in economic activity for Pinal County
- $468 million in taxes and royalties for Arizona government
- $1.98 billion in personal income in Arizona
Over the 30 year life of the project, Florence Copper will create and support an annual average of:
- 796 jobs in the state of Arizona
- 480 jobs in Pinal County
- 170 direct jobs at the project site in Florence