Broken Hill ore deposit

On 5 September 1883, a Mount Gipps boundary rider named Charles Rasp staked a claim on the outcrop because it looked like tin oxide as described in his prospecting guide book.

Broken Hill was exploited initially by small prospectors working the gossan for easily won galena, and soon dozens of shafts were sunk.

Broken Hill South Limited ceased operations in 1972 and its leases were acquired by Minerals Mining & Metallurgy (MMM).

[3] By the early 1950s the Broken Hill area had suffered a major drought of over eight years which was close to shutting down the mining operation.

Over a period of several months, special tanker car trains transported over 250 million gallons of water 40 miles by train which was pumped from the Darling River near Horse Lake, west to the small Mount Gipps rail siding where the water was transferred to large storage tanks that were built for the purpose.

From Stephens Reservoir the water makes another downhill journey by a large pipe to the Broken Hills mining operation.

[4] According to Gustafson, "The Broken Hill lodes are massive lead-zinc sulphide replacement orebodies forming (before erosion) a long continuous, irregular flat, curving pencil of ore roughly 2,000-3,000 high and 300 feet thick.

In longitudinal section, the deposit describes a broad arc, flat in its middle (highest) portion, and pitching downward at each end...continuously mineralized for a horizontal distance of more than 3 miles."

Deformation, folding, and metamorphism converted the sediments into gneiss, the granitic rocks in augen, and the gabbro into amphibolites and hornblende schists.

[1] The ore consists of massive, recrystallised sphalerite-rich, galena-sphalerite and galena-rich sulfide lenses in folded horizons, known as No.

Broken Hill is widely considered to be a sedimentary exhalative (SEDEX) deposit which has been extensively reworked and modified by metamorphism and shearing.

The lower part of the Willyama Supergroup has undergone intense sodium alteration, particularly the Broken Hill Block and subdomain.

The current consensus view is that metasomatic overprints are present as a result of the focusing of flow through the zones of weakness around the massive sulfides, which are ductile failure loci in themselves.

Metasomatic effects include re-equilibrating isotopic systematics of the lead-zinc sulfides and wall-rocks, and introduction of rare elements into the sulfide bodies to form one of the most diverse mineralogical assemblages in the Earth's crust, with 1500 or more mineral species recognized at Broken Hill, including several dozen not reported elsewhere.

The association of the Broken Hill line of lode with a horizon of manganiferous garnets is considered to be partly a function of a potential protolith of exhalative manganiferous chert, metamorphically upgraded to a garnetiferous gneiss, and perhaps some reconstitution of that protolith by metasomatism associated with the nearby massive sulfides.