Xifanping Cu-Au deposit, Yanyuan County, Liangshan Yi, Sichuan, Chinai

Regional Level Types
Xifanping Cu-Au deposit	Deposit
Yanyuan County	County
Liangshan Yi	Autonomous Prefecture
Sichuan	Province
China	Country

Porphyry copper-gold deposit. The mineralization is associated with a multistage quartz monzonite stock that intruded into a sequence of Permo-Triassic clastic rocks.

The mining area is underlain by clastic rock series of the Upper Permian Leping Formation and Lower Triassic Qingtianbao Formation. Hundreds of porphyry intrusions have been found in this area in the form of dikes, with the size of the porphyry bodies generally less than 0.5 km2. Quartz monzonite porphyry and minor vein-like quartz syenite porphyry, lamprophyre dikes, and dioritic porphyrite account for most of the types of rock. Biotite quartz monzonite porphyry comprises the main ore-forming rocks, intruding a Permo–Triassic clastic sequence with hornization alteration. The Cu (Au) ore bodies are mainly situated within or outside of the contact zone between the mineralized porphyry bodies and wall rock.
Alteration of the porphyry bodies at the Xifanping deposit is intense and pervasive. In the plane view, alteration zones from the center of the porphyry bodies to the wall rock consist of a deep K-silicate zone, shallow propylitic zone, and hornfels zone. Porphyry Cu–Au mineralization in the Xifanping deposit grades up to 0.18 Mt Cu (0.28% Cu; 0.31 ppm Au). A multistage biotite quartz monzonite porphyry was the source of this mineralization, which crosscuts a Permian–Triassic clastic sequence.

In the Xifanping mining area, the Upper Permian Leping Formation and Lower Triassic Qingtianbao Formation clastic rock sequences are exposed. The district hosts hundreds of small porphyry intrusions, typically less than 0.5 km2 in area, occurring as stocks and dikes. Quartz monzonite porphyry predominates, accompanied by minor vein-like quartz syenite porphyry, dioritic porphyrite, and lamprophyre dykes. The principal ore-forming phase is biotite quartz monzonite porphyry, which intrudes the Permo-Triassic clastic sequences and is associated with hornfels alteration. Copper–gold ore bodies occur both within and adjacent to the contact zone between the mineralized porphyry and surrounding rocks. The deposit contains reserves of 0.18 Mt Cu, grading 0.28% Cu and 0.31 ppm Au. Mineralization is dominated by porphyry-type assemblages. Cu–Mo ore bodies consist mainly of veinlet- and disseminated pyrite–chalcopyrite–magnetite–native gold ± molybdenite ± galena ± sphalerite, hosted both within porphyry intrusions and along their contacts with clastic wall rocks. Early-stage mineralization is characterized by quartz veins and stockwork ore rich in molybdenite, associated with potassic alteration. Late-stage mineralization consists of veinlet- and disseminated-type ores containing only minor molybdenite, linked to propylitic alteration dominated by chlorite and calcite.

Geochronology

Mineralization age: Paleogene : 37.5 Ma to 29.6 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
Phanerozoic
	Cenozoic
		Paleogene
			Oligocene	ⓘ Molybdenite (youngest age) 29.6 Ma
			Eocene	ⓘ Molybdenite (oldest age) 37.5 Ma

Other Regions, Features and Areas containing this locality

References