Hubei Yangxin jilongshan copper mine

Jilongshan copper mine is located in the east and west of Fengdong mine field. The tectonic position belongs to the lower Yangtze platform fold belt and Tongshan-Ruichang depression fold fault belt.

Second, the mining area geology

See figure 2- 183.

Figure 2- 183 Geological Map of Jilongshan Copper-Gold Deposit

1-thick dolomite, limestone and dolomite in the seventh member of Daye Formation; 2- Thin-thick limestone in the sixth member of Daye Formation; 3— Dolomitic limestone and dolomite with gypsum zone in the fifth member of Daye Formation; 4-thick dolomite limestone in the fourth member of Daye Formation; 5— Thin limestone of the third member of Daye Formation; 6- marble; 7— Permian Changxing Formation limestone; 8- anticline; 9— Inverted anticline; 10-overturning anticline; 11-overturning syncline; 12- Normal fault; 13- reverse fault; 14- breccia; 15- ore body; 16— skarn; 17- granodiorite porphyry; 18- Profile of Exploration Line

(1) stratum

The strata exposed in the mining area are mainly Member 3-7 of Daye Formation of Lower Triassic (t1dy3-t1dy7). T 1dy4, T 1dy5 and T 1dy6 are closely related to the deposit, and their lithologic characteristics and thickness are consistent with those of the Fengshandong deposit mentioned above.

(2) Structure

The fold structure in the mining area is a secondary fold in the core of the Jilongshan-Miaomushan compound anticline, which is followed by Kejiatang anticline, Zhulintang anticline, Guijiashan anticline, syncline and Jilongshan anticline from north to south. The fault structures are mainly NW-trending, EW-trending and NE-trending, among which NW-trending and EW-trending are the main rock-controlling and ore-controlling structures.

(3) intrusive rocks

Jilongshan rock mass is 2,800 meters long and 200-600 meters wide, with an exposed area of about 65,438 0.2 square kilometers. The rock mass is NW-trending, inclined to the southwest, with an inclination angle of 30-60 (lying in the southeast, the SE section is deep, indicating that the rock mass invades from east to west), and the formation depth of the rock mass is less than 65,438 0 kilometers, which is a shallow-ultrashallow diagenetic system.

The main lithology of the rock mass is granodiorite porphyry with porphyritic structure, and the content of porphyry is about 40% ~ 50%, including plagioclase 45% ~ 50%, amphibole 20% ~ 25%, quartz 15%, biotite 10%, and a small amount of microcline (< 5%). The matrix accounts for 50% ~ 60%, with micro-granite structure. The main components are feldspar and quartz, and the auxiliary minerals are apatite, magnetite and sphene. The local stage of granodiorite porphyry changed into contemporaneous monzoporphyry, and later into diorite porphyry vein and lamprophyre vein.

Petrochemical composition: the SiO2 _ 2 content of granodiorite porphyry in this area is 60.64% ~ 64.74%, with an average value of 665,438 0.78%; The content of Na2O+K2O is 6.93% ~ 7.60%, with an average of 7.65438 08%. W (K2O)/W (Na2O) = 0.98% ~1.48%, with an average of1.19%; W (Fe2O3)/W (Fe2O3+FeO) = 0.29% ~ 0.66%, with an average of 0.48%. Compared with similar rocks in China, SiO2 _ 2, Na2O and K2O are slightly higher, W (Fe2O3)/W (Fe2O3+FeO) is higher, SL is higher, FL is similar, and MF is lower.

The contents of gold, copper, silver and molybdenum in rock mass are 9.3 times, 2.2 times, 0.5 times and 2. 1 times that of similar rocks in China respectively.

Three. geology of ore deposits

See figure 2- 184.

Figure 2- 184 Section of Line 36 in Jilongshan Mining Area

G1-contains gold, silver, lead and zinc; G 1- copper-gold paragenetic ore body; G2- Cu-Au paragenetic ore body; 1-dolomitic limestone and dolomite; 2- bedrock; 3- skarn; 4— Ore body

(1) Morphology and occurrence of ore bodies

The deposit consists of 4 1 ore bodies, but the main ore bodies are I, G 1 and G2. The copper and gold reserves of these three ore bodies account for 70% and 94% of the deposit reserves respectively.

Orebody I is distributed in the contact zone of the northern edge of the rock mass, and is layered, extending in the northwest direction, leaning to the southwest, lying on the southeast, with a length of 550m, an average thickness of 4.3m and a depth of 250-300m. It is a copper ore body with associated gold, silver, lead and zinc.

G 1 ore body occurs in the contact zone of marble tongue at the southern edge of rock mass, and the ore body at the end of marble tongue is thick, and the tail of ore body extends in a forked shape between marbles. The ore body is vein-like or tadpole-like, with a length of 600 meters, an average thickness of 6.33 meters, a depth of 80-300 meters and a dip angle of about 20. The ore body is a copper-gold paragenetic ore body (locally copper-associated gold ore body).

The G2 ore body is distributed in the contact zone between another concave part of the G 1 ore body and marble tongue. The ore body is crescent-shaped or vein-shaped, with a length of 300 meters, an average thickness of 5.24 meters and a depth of 60-200 meters, with a lateral dip angle of 30 to the southeast. The ore body is a copper-gold paragenetic ore body.

(2) Ore characteristics

1. ores and minerals

The mineral composition of the ore is complex (Table 2- 1 13). The main copper minerals are chalcopyrite and bornite, and the main gold minerals are natural gold, silver-gold ore and gold-silver ore.

Table 2- 1 13 Mineral Composition of Ore

2. Ore structure

The ore structure includes authigenic, semi-authigenic, irregular granular structure, metasomatic texture, solid solution separation structure and skeleton crystal structure.

3. Ore structure

Ore structures are mainly veinlets disseminated, veinlets-reticulated veinlets, massive, breccia and variegated.

4. Ore grade classification

The ore contains many ore-forming elements, mainly copper and copper. Did you take it? Taking No.1 ore body as an example, the average copper is1.64% (0.31%~14.3%) and the average gold is 2.14×10-6 (0.39 ~ 2.03). In addition, lead is 3.26%, zinc is 5. 16% and molybdenum is 0. 1 18%.

Gold is widely distributed in granodiorite porphyry, skarn and breccia marble in the outer contact zone, and can be divided into gold granodiorite-gold copper mine (in skarn)-gold lead-zinc mine (in the outer contact zone)-gold arsenic mine-Jinjiao-breccia marble from the outside of the rock mass. Among them, gold and copper deposits in skarn are the main ones, which can form copper-gold symbiotic (partial symbiotic) ore bodies. In the outer contact zone, A u coexists with lead and zinc, orpiment and realgar to form an "isolated" gold ore body, which can also be circled in some parts of porphyry body, but this "isolated" gold ore body has low gold grade and small scale, and the correlation coefficient between gold content and copper content is 0.66.

Gold minerals are mainly natural gold, with a small amount of silver-bearing natural gold and silver-gold ore, and occasionally tellurium gold ore. Gold is irregular granular, worm-like, flaky, spherical and chain-like submicroscopic gold. Gold is mainly filled in the cracks of gold-bearing minerals or wrapped in chalcopyrite.

(3) zoning of alteration and mineralization of surrounding rocks

1. Wall Rock Alteration and Zoning

The wall rock alteration mainly includes skarnization, timely sericitization, pyritization, chloritization, epidote and carbonation, locally kaolinite and serpentine, and occasionally weak potash feldspar in the rock mass. These alterations often overlap in space, but there is a certain zoning trend. From the center of rock mass to the outside, it can be roughly divided into: (potash feldspar)-timely sericitization-chlorite, epidotization-skarnization-(serpentine marble). Pyritization and carbonation are widely distributed from rock mass to marble, but pyritization is more developed in porphyry rock mass and carbonation is more developed in external contact zone.

2. Mineralization zoning

Mineralization in this area is mainly in skarn belt, but also distributed in internal and external rocks. From the inside to the outside of the rock mass, it can be divided into copper-molybdenum (gold), copper-gold-silver, gold-lead-zinc, silver-gold (arsenic) and other mineralization zones. The gold content gradually increases from the inside out, and the mineralization scale is the largest in Cu-Au-Ag belt and Au-Pb-Zn-Ag belt.

Four. mineralize

The mineralization process of Jilongshan deposit is multi-stage, which can be divided into gas-liquid stage and hydrothermal stage. Skarn is mainly formed in gas-liquid phase, and molybdenite and magnetite are formed in gas-liquid phase (the mineralization temperature of magnetite is 367℃). The hydrothermal period lasts for a long time and can be divided into three stages: iron-copper sulfide stage, lead-zinc sulfide stage (296 ~ 300℃) and arsenic sulfide stage (198 ~ 202℃).

During the development of ore-forming hydrothermal solution from high temperature to low temperature, the pH value changed from 5.609→7.59→8.44, that is, from acidic to neutral to weakly alkaline. The changing trend of pH value is oxidation-reduction-oxidation.

Table 2- 1 14 Jilongshan type comprehensive prospecting model for gold and copper deposits Table 2- 1 14 Jilongshan type comprehensive prospecting model for gold and copper deposits

The sulfur isotope values of sulfide in ore and granodiorite porphyry are close, and δ34S varies from-2.54 ‰ to+6.1‰, indicating that the sulfur source of diagenesis and mineralization mainly comes from deep places.

According to the above geological and metallogenic conditions, the deposit should be a porphyry-skarn deposit superimposed by medium-low temperature hydrothermal solution.

5. Comprehensive prospecting model of the porphyry-skarn gold-copper deposit in Jilongshan.

(1) geological model

Granodiorite porphyry has invaded many times along the NW-trending fault zone, and in the east-west syncline composed of Triassic carbonate rocks, small rock clusters with complex shapes are superimposed obliquely from morning till night and from top to bottom. At the same time, cryptoexplosive breccia is formed in the outer contact zone at the front end of the rock tongue. The contact zone of rock mass forms a complex skarn-type gold-copper ore body, which is obliquely combined with the NW-trending tension-torsion fault zone in the late stage of rock-controlling structure. The medium-low temperature hydrothermal solution migrates along the favorable compound area of surrounding rock and fault, which makes mineralization superimposed and enriched. The surrounding rocks are altered and developed, and corresponding mineralization zoning appears. The ore is mainly composed of gold and copper, the upper rock mass is iron ore, and the lower rock mass is near silver, lead and zinc.

(2) Geophysical model

The ground magnetic anomaly is in a stable magnetic field. There is low gravity anomaly on the rock mass. The anomaly of electrical method is obvious, and the anomaly of self-electrical low resistance reflects the ore body.

(3) Geochemical model

Element geochemical anomalies with large range, high intensity and obvious concentration gradient are formed in the rock mass distribution area. The outer belt anomaly of copper covers the whole rock mass. The central zone of gold and copper abnormally wraps the ore body. Molybdenum halo is distributed in the contact zone and developed in the lower rock mass. As anomaly is not only distributed in gold-copper ore bodies, but also in the outer contact zone at the front of rock mass.

The comprehensive prospecting model of this deposit is shown in Table 2- 1 14.