The Proterozoic Jinchuan intrusion is located at the margin of the Sino-Korean massif. It intruded into late Archean metasedimentary rocks consisting of gneisses, chlorite-quartz schists, banded marbles and migmatites. The intrusion occurs as a NW oriented lens, over 6000 m long, approximately 200–300 m wide and more than 1100 m thick. The primary magma was a high-MgO basalt.

The intrusion chiefly consists of five rock types. In order of decreasing abundance these are lherzolite, dunite, plagioclase lherzolite, olivine websterite and websterite. It is subdivided in an upper layer (consisting of ultramafic cumulate: dunite and olivine-rich lherzolite), a lower layer (consisting of olivine-poor lherzolite, plagioclase lherzolite and websterite) and a marginal layer (consisting of websterite and chlorite-tremolite schists).

The deposit is divided into four segments by E–W to NE–SW trending strike-slip faults. Each of these segments comprises a mine; these are referred to as mines III, I, II and IV, from west to east. Most of the intrusion (mines I and II) is exposed, except for two isolated parts (mines III and IV) that are covered by Quaternary alluvium.

The sulfide ore bodies are situated in the middle and lower regions of the intrusion, with the major orebodies of Mines I and II accounting for more than 90% of the known Ni–Cu reserves in the deposit. Sulfide minerals generally increase in abundance towards the base of the complex. Nickel sulfides are the dominant ores; they are disseminated to net-textured, with sulfide contents ranging from 1-40% by volume. Massive sulfide ore is rare.

The Jinchuan deposit, with > 500 million tons of sulfide ores, is one of the largest nickel-copper sulfide deposits in the world. The distribution of PGE in BMS of the Jinchuan deposit using in-situ accelerator mass spectrometry analysis and found that ∼ 70% of Pd and > 46% of Os, Ru, and Rh are accommodated by pentlandite as solid solution. Recent studies based on samples of orebody I-24 of the Jinchuan deposit show that mostly Pt, Rh and Ir of the Jinchuan sulfide occurred as PGM associated with semimetals, which resulted from the formation of (Ir-Rh-Pt)AsS pre-nucleation clusters under a relatively lower fO2 (∼ QFM + 1) condition.

The Jinchuan deposit contains more than 500 million metric tons of ore with 1.1 wt % Ni and 0.7 wt % Cu. The ore hosted ultramafic intrusion was emplaced as a sill-like body with length of ~6,500 m, width of ~300 m, and vertical downward extension >1,100 m in its central part. This intrusion is divided into four segments by a series of NE-trending strike-slip faults. These segments were numbered as III, I, II, and IV from west to east by the mine geologists based on the order of mine development.

World's third largest Ni deposit.

Geochronology

Mineralization age: Neoproterozoic : 833.2 ± 1.8 Ma to 826.3 ± 2.1 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Precambrian
	Proterozoic
		Neoproterozoic
			Tonian	ⓘ Zircon (youngest age) 826.3 ± 2.1 Ma ⓘ Zircon (oldest age) 833.2 ± 1.8 Ma

Other Regions, Features and Areas containing this locality

References