The Chino copper mine, also known as the Santa Rita copper mine, located in south-western New Mexico, in the US is one of the oldest copper mines in North America and one of the first low-grade, open-pit copper mines in the world.
The Chino open-pit copper mining complex is fully owned and operated by Freeport McMoRan.
The Chino mine commenced production with the commissioning of the original concentrator in 1911 which was replaced by a new facility in 1982. A smelter for the mine was commissioned in 1939 and was upgraded in 1985 before its permanent closure in 2005.
The mine was owned and operated by Mitsubishi Materials Corporation from 1986 to 2003 and by Phelps Dodge Corporation from 2003 to 2006.
Freeport McMoRan became the owner and operator by acquiring Phelps Dodge Corporation in 2007 and placed the mine under care and maintenance in 2008 before restarting mining and milling operations at the site in 2011.
Copper production at Chino
The Chino open-pit mine produced 175 million pounds (Mlbs) of copper in 2019, compared to 173Mlbs in 2018 and 215Mlbs in 2017.
The mining and milling operations were temporarily suspended due to the spread of COVID-19 among few employees of the mine in April 2020.
Project location and geology
The Chino Copper mine is located in Grant County of New Mexico, approximately 24km east of the Silver City historic mining community. The project area encompasses approximately 117,300 acres.
Situated in the Basin and Range province along the southern margin of the Mogollon-Datil volcanic field, Chino is considered to be the biggest porphyry copper deposit in New Mexico.
The deposit comprises sediments, flows, and alluvium overlaying a Precambrian basement of schist and granitic rocks. The sediments consist of Paleozoic limestone of the Cretaceous Age and Tertiary lava with interbedded sands and gravels.
Mineralisation and ore reserves
The copper mineralisation at Chino is found disseminated in porhyritic diorite, granodiorite, monzonite, or quartz monzonite. Chrysocolla is the predominant oxide copper mineral at the deposit.
The Chino mine was estimated to hold 324 million tonnes (Mt) of proven and probable ore reserves tonnes grading 0.45% copper and containing approximately 2.7 billion pounds of copper as of December 2019.
Mining operations at Chino
The conventional open-pit mining method involving drill, blast, load and haul operations are employed at the Chino mine.
The current mining fleet comprises thirty-five 240t haul trucks and four shovels with bucket sizes ranging from 31m3 to 48m3 that are capable of loading approximately 235,000 tonnes (t) of ore materials a day.
The Chino mine complex is divided into three main areas namely, the North Mine Area, the Pipeline Corridor Area, and the South Mine Area.
The North Mine Area hosts the Santa Rita open-pit that currently measures 2.8km-long and 1,350feet-deep, as well as the leach ore stockpiles, waste rock stockpiles, the sulphide extraction, and electrowinning (SX/EW) plant and the Ivanhoe concentrator.
The Pipeline Corridor Area extends from the Ivanhoe concentrator to the north end of the Lake One and the Hurley Operation Area. It includes three tailings pipelines, one process water pipeline, one concentrate pipeline, and associated infrastructure.
The South Mine Area encompasses the reclaimed tailing ponds. The tailing impoundments cover approximately 3,500 acres and contain approximately 690Mt of tailing.
The Chino mine complex houses a 36,000 tonnes per day (tpd) to produce copper and molybdenum concentrate, as well as a sulfide extraction and electrowinning (SX/EW) plant capable of producing up to 150Mlbs of copper cathode a year.
The run-of-the-mine (ROM) ore from the primary crusher at the Santa Rita open-pit undergoes secondary crushing and grinding followed by conventional froth-flotation at the Ivanhoe concentrator for the production of copper and molybdenum concentrates.
The SX/EW produces copper cathode by processing the solution generated by ROM leaching.
The project area is accessible through paved roads connecting the State Highway 180. The mine site is also accessible by rail.
The electricity requirement is met through power supply from the 570MW gas-fired Luna Energy combined-cycle facility that is operated by the Public Service Company of New Mexico. The mine also receives electricity from the open market.