Fengcheng Fortune Teller _ Fengcheng Fortune Teller

Xiaotongjiapuzi Gold Mine, Fengcheng City, Liaoning Province

Xiaotongjiapuzi gold deposit is located in the east of Qingchengzi lead-zinc ore field in Liaodong. 1993, a large concealed rock gold deposit (Liu Guoping, 1998) was discovered by 103 geological team affiliated to China Nonferrous Metals Industry Corporation after summarizing the gold mineralization law.

The discovery of Xiaotongjiapuzi gold deposit is of great significance. In space, the general survey of gold deposits has been expanded from Dashiqiao Formation of Liaohe Group to Shanggaixian Formation. Geographically, the gold exploration area extends from the periphery of Qingchengzi mining area to the schist distribution area of Gaixian Formation in Liaohe Group, which opens up a new prospecting field. According to the metallogenic geological law of Xiaotongjiapuzi gold deposit, Liaoning Nonferrous Geological Exploration Institute has successively discovered small and medium-sized deposits such as Wangou, Linjiasandaogou, Baiyusandaogou and Jiapigou in the schist of Gaixian Formation, and the prospecting scale is still expanding, with broad prospects (Cai, 1999).

The main mineralization types of this deposit are quite special. In addition to the gold-bearing siliceous rock type, the gold-bearing biotite granulite type was discovered for the first time, which is of guiding significance for the deep prospecting of gold polymetallic in the western Liaodong rift.

1 regional metallogenic geological environment

1. 1 geotectonic unit

The tectonic position is located in the eastern part of the northern margin of North China Platform, in the Tertiary fault basin of the Paleoproterozoic Liaoji intracontinental rift. Regionally, Zhujiapuzi-Xinling-Huangdianzi syngenetic fault is divided into eastern fault depression area and western fault uplift area.

In the eastern fault depression area, a set of metastable clastic rocks-carbonate rocks were deposited. The jet rocks related to gold deposits, such as siliceous rocks and layered tourmaline-bearing granulite, are confined to the vicinity of the fault-depression syngenetic faults and spread in the northwest direction, and the submarine gas-liquid jet center appears in breccia siliceous rocks. The jet rock in the center is the main rock of gold mineralization, far from the center, and the gold mineralization is mainly distributed in the upper five layers and the contact layers of the fifth and fourth layers of the third member of Dashiqiao Formation. Xiaotongjiapuzi Gold Mine is located in this area (Anton, 2004).

1.2 regional stratum

Figure 1 Geological Schematic Diagram of Xiaotongjiapuzi Gold Mine Area

(Revised according to the data of Liaoning Nonferrous Geological Team 103, quoted by Liu Guoping 1998).

1- Cretaceous volcanic rocks; 2- Gaixian Formation of Liaohe Group; 3- Dashiqiao Formation of Liaohe Group; Liaohe Group 4- Langzishan Formation; 5 yuan ancient mixed granite;

6- Fault. -Early Indosinian granite; -Late Indosinian granite; β μ-diabase; γ 2 yuan ancient sodic granite

The mining area is located in the paraxial part of the western end of Liaodong Rift, that is, the eastern part of Sanjiazi-Fang Jia shallow lagoon, and consists of metamorphic rock series of Liaohe Group (Figure 1). The Paleoproterozoic sedimentary metamorphic Liaohe Group in Luliang area is a set of extremely thick clastic rocks, carbonate rocks and pyroclastic rocks. Liaohe Group is divided into Yujiapozi Formation, Langzishan Formation, Dashiqiao Formation and Gaixian Formation from bottom to top.

Yujiapozi Formation is a boron-bearing rock series mainly composed of mixed metamorphic granulite and granulite, which was formed during the rift expansion period and deposited with extremely thick acid-base volcanic rocks, with the thickness exceeding1000 m.

The Langzishan Formation is an interlayer zone composed of diopside granulite, plagioclase amphibole, granulite, biotite schist and banded marble. The original rock is terrigenous clastic rock-clay rock, which is deposited by underwater volcano, and the thickness varies from 10 to 200 meters.

Dashiqiao Formation is characterized by marble intercalated with schist and granulite, which was formed in the transgression period of large depression. Qingchengzi is located at the edge of Sanjiazi Fang Jia Basin, forming flysch carbonate formation, which is divided into three sections from bottom to top, one is carbonate formation, the other is clay formation, and the third is carbonate formation mixed with intermediate-acid pyroclastic formation. It is especially developed in the third member of this area and can be divided into five layers, of which Dashiqiao Formation is 500 ~1500m thick.

Gaixian Formation, formed in the contraction period of rift valley, is a set of clayey rocks-semi-clayey rocks with regressive series, biotite schist, biotite schist mixed with siliceous schist, biotite granulite, tremolite granulite and marble, with gold mineralization at the bottom, with a thickness of > 500m (sunny sun, 1997).

1.3 regional tectonic framework

The regional structure in this area shows multi-stage and complexity, and the basement structure is mainly east-west Since Phanerozoic, fault structure has been the main framework of regional structure (Liu Guoping, 1998). In Mesoproterozoic, that is, the Liaodong Rift Valley recovered to the early uplift stage, and gentle and wide folds were formed in the area, which were Xinling anticline, Shikangshu syncline, Bellazi-hazel gully anticline and Nanshan syncline from north to south in turn. NEE-SWW nappe occurred in Neoproterozoic mining area, which caused strata inversion, and basement migmatite and mixed granite napped on Liaohe Group, forming a ductile-brittle imbricate nappe structure with nearly north-south strike. During the middle and late Indosinian-Yanshan period, with the continuous narrowing of the active continental margin of the Pacific plate, two sets of faults in NE direction and NW direction appeared in the mining area, and at the same time, a set of gentle and wide folds in NE direction developed, which overlapped with the early basement folds to form a structure spanning the vault and depression (Cai, 1999).

1.4 regional magmatism

Proterozoic and Mesozoic mining areas have strong magmatic activity, mainly including Proterozoic Zhujiapuzi potash granite, Mesoproterozoic Dadingzi, Jianshanzi, Fangjiazi and Shijialing sodium granite, and Mesozoic Shuangdinggou, Xinling porphyritic and porphyritic intermediate-acid granite. Dadingzi pluton is the sodic granite with the largest exposed area in Liaodong rift orogenic belt, located in the northern contact zone of Zhujiapuzi potash granite, surrounded by Jianshanzi, Fangjiafengzi, Shijialing and other small sodic granites, and its emplacement age is1740 ~1621Ma (K-Ar method, Zong Rui There are lead, zinc mineralization and iron-manganese carbonation in marble on both sides, and granite itself is also broken and kaolin. Shuangdinggou, Xinling porphyry granite and porphyry granite occur in rock mass or bedrock, and their emplacement ages are 230.7±5ma and 265,438+07.6 ~ 226.7 Ma respectively (K-Ar method, Rui Zongyao et al., 65,438+0994; Dai Junzhi, 2006). Yanshanian Lanhualing and Xiongdishan granitoids (K-Ar method,141~161Ma). All the above-mentioned rock masses are remelted granite, and geophysical data confirm that their deep occurrence is bedrock, which constitutes a good trap environment (Hu Tiejun, 200 1).

1.5 metallogenic unit

The gold metallogenic units are located in Tarim-North China metallogenic domain, North China landmass metallogenic province and Yingkou-Dandong metallogenic belt.

2 Mining area geology

2. 1 ore-bearing strata

The gold deposit is located at the dip end of Zhengou dip anticline, an exotic block of Qingchengzi nappe structure. It mainly develops in the third member of Dashiqiao Formation and the fourth and fifth floors of Gaixian Formation (Figure 2). The lower part of the fourth layer of the third member of Dashiqiao Formation is granulite, the middle part is banded marble and the upper part is garnet biotite schist. The fifth layer of the third member of Dashiqiao Formation is dolomite marble mixed with andalusite marble and sillimanite biotite schist. Gaixian Formation is mainly composed of schist and granulite. A layer of biotite granulite is often developed between the fourth and fifth layers of the third member of Dashiqiao Formation, and siliceous rocks are distributed at the contact surface between Dashiqiao Formation and Gaixian Formation, which is lenticular along the layer and obviously controlled by the horizon. Siliceous rocks are dark gray, dense, massive, breccia and porous. The mineral composition is timely (content > 90%), chalcedony, sericite, calcite, carbon and iron, and tourmaline, topaz and oolitic chlorite are occasionally seen. The timely grains are obviously elongated and wavy, chalcedony is often explained in blocks, and trace elements are rich in Au, Ag, Mo, S, As, P, but poor in Cu and Zn. Rock is a porous structure (gas escapes). The biotite granulite is gray, fine-grained and banded. The mineral composition is microcline (particle size 0.05 ~ 0. 15 mm, content 45%), timely (particle size 0.05 ~ 0.3 mm, content 25%) and biotite (content < 15%). The accessory minerals are tourmaline and apatite. Silicification, pyritization and arsenopyrite are closely related to gold, and their original rocks are marine acidic volcanic rocks in Liaohe period. The overall strike of the stratum is 70 ~ 80, with NW dip angle10 ~ 30 (Zhao Guangfan, 1997).

Fig. 2 Plane geological schematic diagram of the middle section of Xiaotongjiapuzi Gold Mine 104m.

(According to the data of Liaoning Nonferrous Geological Team 103)

1- fracture; 2- ore body; 3- Broken zone; Tetramica schist of Gaixian Formation in Liaohe Group; 5— Five-layer marble in the third member of Dashiqiao Formation of Liaohe Group; Garnet mica schist in layer 6-4 of Dashiqiao Formation in Liaohe Group; 7— Four-layer marble in the third member of Dashiqiao Formation of Liaohe Group; 8— The fourth layer granulite of the third member of Dashiqiao Formation in Liaohe Group.

The ore-bearing strata can be divided into three layers from top to bottom, and the contact part between the lower part of Gaixian Formation and marble of Dashiqiao Formation is the occurrence part of 1 Ag-Au deposit in this area.

Five layers of the third member of Dashiqiao Formation (marble). It is the main surrounding rock of gold ore bodies, and the siliceous rocks in Xiaoshimengou area in the east of the mining area are themselves gold ore bodies (1 gold ore belt). The middle part of this layer is the occurrence part of I- 1 gold belt. The contact part between the lower part and garnet (siliceous line) biotite schist in the third member of Dashiqiao Formation is the occurrence part of No.2 gold belt in the mining area.

The fourth layer of the third member of Dashiqiao Formation can be divided into upper, middle and lower layers: ① The upper garnet (sillimanite) biotite schist is characterized by gray or grayish white garnet (sillimanite) biotite schist with a thickness of 0~ 15m ~ 50m, and there is a thin layer of biotite granulite at the contact position between the upper layer and the fifth marble of the third member of Dashiqiao Formation with a thickness of 0~65438. It is the marker layer of the boundary between the fifth floor of the third member of Dashiqiao Formation and the fourth floor of the third member of Dashiqiao Formation, and it is also the occurrence site of the No.3 gold belt in the mining area. (2) The marble stratum in the middle part is similar to the fifth floor of the third member of Dashiqiao Formation, but its thickness is thin, and it has the characteristics of repeated pinchout in strike extension and dip extension. ③ The lower part of granulite is obliquely long, and the boundary of original rock is between igneous rock and sedimentary rock, which belongs to intermediate-acid tuffaceous rock (Anton, 2004).

2.2 magmatic rocks in mining area

The spatial location of the deposit is obviously restricted by the structural type and the distance from the Indosinian-Yanshanian intrusive rock mass. It is known that gold ore bodies are mostly distributed in the range of 1km from Indosinian-Yanshanian intrusive rock mass, and the depth of 1500m (frequency response) in the mining area is occupied by rock mass (Zhao Guangfan, 1997). Outside this range, even if there is tectonic space, there is generally no gold ore body (Cai, 1999).

2.3 Ore-controlling structure

The gold ore body is located in the northeast wing of the back shape of Xiaotongjiapuzi in Zhenzigou dipping anticline, which is formed by the intersection of two groups of anticlines. The dome-shaped subsidence space controls the gold mineralization of the whole mining area (Cai, 1999). Before mineralization, there was Jianshanzi fault with strike of 330, dip of NE, dip angle of 60 ~ 80, extension of 20km and width of 10~20m ~ 20m. Mylonization is common in this area, with loose fragments in some areas, obvious multi-stage activities and high contents of gold, silver and arsenic. There are mainly two bedding sliding faults during the metallogenic period. In the east of the mining area, there is a 1 ore belt along the contact surface between Dashiqiao Formation and Gaixian Formation, which extends 500m and has a depth of 200 ~ 600 m. In the transitional interlayer zone between the fourth and fifth floors of the third member of Dashiqiao Formation in the west of the mining area, there is a No.2 ore belt in the interlayer structural control zone with a depth of 300 meters ... After mineralization, there are mainly two groups of faults in northeast and northwest directions, which are distributed at different stratigraphic interfaces and nearby, and there is no obvious dislocation to the ore body, with a small extension depth. They are all normal faults, which are caused by disordered secondary tensile cracks along the contact surface and its vicinity during the deformation of plastic and brittle rocks (Zhao Guangfan, 1997).

2.4 surrounding rock alteration

Wall rock alteration mainly includes silicification, carbonization, graphitization, pyritization, sericitization and chloritization, among which silicification, pyritization, carbonization and graphitization are most closely related to gold and silver mineralization and run through the whole mineralization process (sunny day, 1997).

Alteration has a certain zoning, and the alteration of dolomite marble from surrounding rock to the center of ore body can be roughly divided into four zones. ① Dolomite marble, without obvious alteration; ② In the veinlet silicified zone, veinlets and reticular veins develop in time, and argillaceous (mainly sericite) also develops; ③ In the strongly silicified zone, timely veinlets and reticular veins are developed, and silicified metasomatic carbonate is also strong, with residual breccia and isolated island carbonate, and local rocks are in breccia structure; ④ In the silicified rock zone, the timely veinlet filling and silicification metasomatism are very strong, carbonate is almost completely metasomatized, and kaolin and pyrite-arsenopyrite are locally developed, and the ores with higher gold content are mainly in the zones ②, ③ and ④ (Liu Guoping, 1998).

3 Geological characteristics of ore bodies

3. 1 deposit (entity) characteristics

Xiaotongjiapuzi gold deposit is divided into three mineralization zones.

Mineralization zone I is located at the contact position between schist of Gaixian Formation and the fifth layer of the third member of Dashiqiao Formation. The occurrence is consistent with the stratum, with an overall extension of 500 meters and a depth of 200-600 meters. It strikes nearly east-west, inclines to the north, and the dip angle is 25. Mineralization in the belt is discontinuous, generally ore bodies occur in the ups and downs of strata, and ore bodies 1 mainly occur in the belt.

Mineralization zone ⅱ is a large gold mineralization zone in this area. The continuous output from west to east has been controlled to extend 600 meters, extend 300 meters, have a width of 2-25 meters, strike 285, dip NE and dip 25. The mineralized zone occurs in the transition zone between ternary five-layer marble and ternary four-layer schist, and its occurrence is consistent with the stratum, and the rocks in the zone are broken and mineralized strongly. Alterations such as graphitization, arsenopyrite, silicification and pyritization are developed, and the No.2 ore body is mainly produced in this zone.

The Ⅲ mineralized zone occurs in the transition zone between the top of dolomite marble in the middle of the third member and garnet mica schist in the upper part. In this area, rock deformation is strong, schistosity and graphitization develop strongly, and the spatial continuity of mineralization zone is good, which is basically consistent with the occurrence of strata, with strike of 70 ~ 80, dip of N, dip angle of 25, extension of 1000 m, extension of 500 m and width of 2 ~ 10 m .. The gold mineralization of this mineralization zone is relatively weak. It mainly produces No.III ore body. In addition, there is an interlayer detachment fault in the lower part of the 1 mineralization belt, and its occurrence is consistent with the stratum, with a strike of 285 and an inclination of 25, and the 1- 1 ore body is developed in the area.

More than 30 gold ore bodies have been discovered in three mineralization zones, among which 1 is the largest ore body, which occurs in 1 mineralization zone, mainly of siliceous rock type, with layered and lentil ore bodies (Figure 2). Ore-bearing rocks include siliceous rocks, silicified marble and biotite granulite. The intensity of gold mineralization is closely related to the deformation intensity of rocks and the content of pyrite and fine arsenopyrite.

I- 1 ore body is an independent gold ore body, which occurs in the mineralization zone 1 in the silicified fractured marble in the middle of the fifth floor of the third member of Dashiqiao Formation. The ore body is layered lentil-shaped and consists of six industrial ore bodies. The single ore body is 80-200m long and 0.7-5.86m thick, in which the western ore body is thinner and the eastern ore body is thicker. The extension depth of the ore body exceeds the extension, and the maximum controlled depth is 70 ~ 300 m. The occurrence of the ore body is consistent with the stratum, with a strike of 70 ~ 90, a dip of N and a dip angle of15 ~ 27. Due to local structure, the occurrence has changed. The occurrence elevation of the ore body is 50 ~ 200 m, and the mineralization type is gold-bearing silicified marble, and sulfide-rich gold, silver, lead and zinc bodies are found locally. The average grade of ore gold is 3.33× 10-6.

No. II ore body occurs inNo. II ore body. The Ⅱ mineralization belt is an independent ore body. It is layered lentil-shaped and occurs in the transition zone between the third member of five-layer marble and the third member of four-layer schist in Dashiqiao Formation, and the occurrence of ore bodies is consistent with the stratum. There are three industrial ore bodies (veins) in the area, with a single vein extending 70 ~ 200m, a thickness of 0.96 ~ 17.29m, a local area of 29.63m and a controlled extension of 360m. The occurrence of ore bodies is consistent with the structural belt, with the strike of 70 east, 90 west and the dip angle of 65438+00 ~ 30 north. The occurrence elevation of ore bodies is 50 ~ 200 m, and the ore bodies are mainly graphitized marble and silicified biotite granulite mineralization. The average grade of the eastern section is 2 1.50× 10-6, and that of the western section is 4.56× 10-6 (Liu Hongxia, 2006).

3.2 Ore Composition and Ore Type

The mineral composition of gold deposits is complex. The main metal minerals are pyrite, sphalerite and galena, followed by arsenopyrite, chalcopyrite, chalcocite, stibnite and galena. Pyrite and Yingshi are the main carrier minerals of gold. Precious metal minerals include natural silver, gold-silver ore, tetrahedrite, crimson silver ore and brittle silver ore. Gangue minerals are mainly timely and dolomite, followed by calcite and sericite. There are differences in mineral assemblages of different types of ore bodies.

The ore types of gold deposits can be divided into four types: siliceous gold deposits, silicified marble gold deposits, altered biotite granulite gold deposits and altered garnet (siliceous) biotite schist gold deposits (Anton, 2004).

3.3 Ore fabric and metallogenic stage division

Ore structures mainly include semi-autotype-allotype granular structure, semi-autotype-autotype granular structure, metasomatic residual structure and solid solution separation structure, followed by inclusion, dissolution and crushing structure. The ore structure is sparse disseminated, massive, breccia-like, crystal cave-like, banded and veinlet disseminated (Cai, 1999).

According to the data of mineral composition, fruit setting and inclusion temperature measurement, the metallogenic process can be roughly divided into three main metallogenic periods. ① Polymetallic sulfide stage. The metallogenic temperature is 130 ~ 150℃, which is equivalent to the initial source bed formed by sedimentation-volcanism, and a large number of metal sulfides are developed. The alteration is mainly silicification and pyritization. Metal sulfides are mostly disseminated, and veinlets are disseminated. The mineral assemblage is pyrite-galena-sphalerite-gold mineral. The main minerals are pyrite, sphalerite, galena and Yingshi. Secondary minerals include chalcopyrite, arsenopyrite, tetrahedrite, silver-gold ore, natural gold and dolomite. ② Synchronism-arsenopyrite-gold deposit period. The metallogenic temperature is 2 10 ~ 230℃, which is closely related to the uplift of Liaodong rift, volcanic eruption, superimposed transformation of metamorphic hydrothermal solution and the enrichment and integration of gold polymetallic sulfide in the source bed. The alteration is mainly silicification, pyritization and sericitization. Metal sulfides are dispersed, disseminated, massive, densely disseminated and banded. The mineral assemblage is timely-arsenopyrite-gold mineral. The main minerals are arsenopyrite, pyrite and timely; The secondary minerals are white iron ore, dolomite, calcite, sphalerite, chalcopyrite, tetrahedrite and sericite. ③ The chronological-dolomite-gold deposit period. The metallogenic temperature is 300 ~ 400℃, which belongs to the Indosinian-Yanshan magmatic hydrothermal transformation metallogenic period. Alterations include pyritization, galena mineralization, sericitization and chloritization. Metal sulfides are generally dispersed and disseminated, veined, caverns and breccia. The timely mineral assemblage is dolomite-gold deposit. The main minerals are silver-gold ore, crimson silver ore, natural gold and timely; Secondary minerals include pyrite, galena, sphalerite, jamesonite and dolomite (Cai, 1999).

4 genesis of ore deposit

4. Geochemical characteristics of1element

Liu Guoping (1998) system collected samples of ore and surrounding rock near the mine, which has the following characteristics.

1) Gold, arsenic and antimony constitute an important ore-forming element combination.

2) 2) The contents of Cu, Pb, Zn and other mineral elements in silicified marble are uniform, but there is a big difference between normal marble and silicified marble, and the contents of Pb and Zn in silicified marble are high, which is consistent with veinlets and disseminated light-colored sphalerite seen in silicified marble in the field and under microscope.

3) The content of manganese in silicified rock and silicified marble is higher than that in common marble, which indicates that manganese was brought in during mineralization and alteration.

4) From normal marble to silicified marble to silicified rock, the content of Sr decreases and the content of Ba increases, and the value of Sr/Ba changes from > 1 to < 1.

5) There is no obvious difference in the contents of iron group elements such as titanium, chromium, vanadium, cobalt, nickel, zirconium, hafnium, niobium, tantalum, thorium and vanadium. Between ore and surrounding rock (including metamorphic rock, marble, lamprophyre, schist, etc.). ) (Liu Guoping, 1998).

4.2 Characteristics of mineral inclusions

4.2. 1 type and development degree

There are abundant primary fluid inclusions in the deposit, mainly water-bearing fluid inclusions, a small amount of CO2 inclusions, three-phase inclusions containing CO2 (about 5%) and multiphase inclusions containing daughter minerals.

The 1) aqueous solution inclusions are composed of pure aqueous solution phase or gas-liquid two-phase at room temperature, and the gas-liquid ratio is generally between 5% and 20%, most of them are around 10%, the size is generally 3 ~ 18 micron, and some of them are 20 ~ 30μ m. The common forms are negative crystal form, irregular quadrangle and triangle. , randomly grouped or independently distributed.

2)CO2 inclusion, which is pure CO2 liquid phase or CO2 gas-liquid two-phase inclusion at room temperature. Such inclusions are mainly CO2-rich liquid phase and a little CO2-rich gas phase, and the proportion of CO2 in gas phase is generally 10% ~ 40%. Generally, the size of such inclusions is between 5 and 20 microns, and most of them are between 8- 15 microns, with various shapes such as ellipse, negative crystal and irregular quadrangle (Dai Junzhi, 2006).

Inclusion composition

Table 1 lists the composition of ore-forming fluid inclusions. The gas phase is rich in volatile substances such as H2O, CO2, CH4 and CO. The liquid components are high in Na+ and Cl-, poor in F- and high in salinity (8% ~ 10%). The nature of ore-forming solution is Na+-Cl- type, and Na+/K+ is an important index to distinguish fluid properties. The ratio of magmatic hydrothermal solution is less than 1, and the ratio of hot brine is higher. The ratio of sodium to potassium in the deposit is 2.25 ~ 6.98. The high content of CH4 and CO in the gas phase indicates that gold mineralization is in a reducing environment (Zhao Guangfan, 1997). Cai (1999) thinks that CH4-rich and organic matter reflect the characteristics of mainly interbedded fluids and a small amount of post-magmatic hydrothermal fluids.

Table 1 Time-dependent Inclusion Analysis Results of Xiaotongjiapuzi Gold Deposit w(B)/ 10-6

Note: The testing unit is Liaoning Institute of Nonferrous Geology and Mineral Resources. According to Cai, 1999.

4.3 Physical and chemical conditions

Homogeneous temperature measurement shows that the metallogenic temperature range of Xiaotongjiapuzi gold deposit is 140 ~ 240℃, and the peak value is around 200℃ (Liu Guoping, 1999). The temperature measured by homogenization method is 145 ~ 174℃, and the metallogenic temperature is medium-low temperature (Zhao Guangfan, 1997). The homogeneous temperature range of inclusions is 1 10.4 ~ 335.2℃, and the peak temperature range is 150 ~ 190℃ (Dai Junzhi, 2006). The salinity of the fluid is 3.9% ~ 16.2%, and most salinity values are between 6.5% ~ 10.5% (Dai Junzhi, 2006).

According to the temperature-density relation equation of inclusions in salt solution, the density of hydrothermal solution is estimated to be 0.77 ~ 1.02g/cm3, and the average density is 0.95 g/cm3 (Dai Junzhi, 2006).

4.4 Isotopic geochemical markers

4.4. 1 sulfur isotope

The δ34S of ore sulfur are all positive, ranging from 1.87‰~ 15.98‰, with a variation range of14.1‰, with an average of 7.85‰ (Table 2). The δ34S of Dashiqiao Formation is 0. 15 ‰ ~ 13.20 ‰, and the δ34S of Indosinian rock mass is 0.5 ‰ ~ 7.6 ‰, with similar sulfur isotope values. However, pyrite in Dashiqiao Formation is developed, mostly in the form of raspberry ball and flake, and there are few sulfides in the rock mass, so the ore sulfur mainly comes from Liaohe Group, with a small amount. Δ Δ 34s between minerals in the ore body has the law of pyrite > sphalerite > galena, which shows that the sulfur isotope composition in the same ore-forming solution is uniform and the sulfur isotope exchange between minerals is balanced (Zhao Guangfan, 1997).

Table 2 Sulfur Isotope Analysis Results of Ore

Note: The analysis unit is Shenyang Institute of Geology, 1995. According to Fan et al., 1997.

Hydrogen and oxygen isotopes

The variation range of time δ 18O in ore is 6.42‰~ 10.70‰, the variation range is 4.28‰, and the average value is 8.36‰. The δD of ore-forming solution ranges from-79.7 ‰ to-48.0 ‰, with a range of 365,438 0.7 ‰ and an average of-65.65,438 0 ‰. The calculated ore-forming solution is -8.63 ‰ ~-2.82 ‰, with an average value of -6.40‰. The δ 18O-δD diagram of ore-forming fluid is basically drawn near the rain line (Figure 3), and the ore-forming hydrothermal solution is mainly atmospheric precipitation (Zhao Guangfan, 1997). Liu Guoping (1999) obtained the corresponding δ 18O value of oxygen isotope composition, which was18.5 ‰ ~ 21.1‰, showing the characteristics of δ 18O drift.

Fig. 3 Relationship diagram of ore time δ18o-δ d.

(According to Zhao Guangfan 1997)

4.5 Rare Earth Elements

1) Compared with rock mass, the total amount of rare earth (σσREE) in most strata is lower than that in rock mass. Between the surrounding rocks of different strata, the total amount of rare earth in argillaceous rocks is generally higher than that in carbonate rocks, and the total amount of rare earth is decreasing from old to new.

2) The ratios of light and heavy rare earths in strata, rocks and ores are all positive. On the rare earth distribution pattern map, the curve is high on the left and low on the right, which belongs to the light rare earth enrichment type (Figures 4 and 5). The δEu anomaly is 0.53 ~ 1.90, which belongs to weak negative anomaly to normal type. It is worth noting that the gold ore body and its host rock δEu < 1, Eu is weak loss type. On the contrary, the surrounding rocks and rock masses far away from the gold ore bodies present Eu positive anomalies, reflecting that there are great differences between the ore bodies and ore-bearing surrounding rocks and adjacent strata and rock masses in the evolution mode and material source of rare earth elements, indicating that the ore-bearing strata have certain specificity.

Distribution model of rare earth elements in surrounding rocks and ore bodies of Xiaotongjiapuzi gold deposit.

Distribution model of rare earth elements in rock mass and ore body of Xiaotongjiapuzi gold deposit.

3) The total amount of rare earth in gold ore bodies is similar to that of host rocks, and the distribution curve of rare earth is very similar to that of host rocks, especially breccia marble and siliceous rocks, which reveals that layered and layered gold bodies have similar sedimentary diagenesis and metamorphic transformation processes with host rocks, and their genetic relationship is close. However, the REE distribution curves of gold ore bodies and rock bodies are not well bridged and lack similarity, while the REE evolution characteristics of Indosinian rock bodies and Yanshanian granite porphyry, lamprophyre and diorite porphyry have obvious similarity and continuity. These indicate that Indosinian-Yanshanian magmatic hydrothermal solution and its mineralization have different geological and geochemical environments and metallogenic conditions from sedimentary metamorphism (Cai,1999); However, Zhao Guangfan (1997) thinks that the total rare earth content and δEu of gold-bearing siliceous rocks are 0.48 (Table 3), and the distribution curve pair shows that it is close to the average value of the upper crust. However, the distribution curve of rare earth elements is different from that of five-layered dolomite marble in the third member of Dashiqiao Formation and Dadingzi plagiogranite, which seems to indicate that siliceous rocks have different origins from sedimentary rocks and intrusive rocks in the same period.

4.6 metallogenic age

The K-Ar age of gold-bearing altered rocks is 206~272 Ma, and the mineralization period is equivalent to the diagenetic period of the Indosinian Xinling granite (Zhao Guangfan, 1997).

The 40Ar/39Ar plateau age and isochron age of sericite in gold-bearing altered rocks are 65438±067±2ma and 65438±067±4ma, respectively. The isotopic ages of rock samples were determined by K-Ar method, in which 1 is sericite metasomatic gold deposit, and 3 is fresh lamprophyre sample and lamprophyre vein cut by gold ore body. The other two lamprophyre samples are mining dikes, which have no obvious intersection with gold ore bodies, and their surface ages are very close, namely 130 Ma and 149 Ma, respectively, representing Yanshanian magmatism. Inferred from the relationship between gold deposits and lamprophyres, the metallogenic age of gold deposits should be < 2 1 1 Ma, but it is impossible to determine whether it is Indosinian or Yanshanian. The K-Ar surface age of sericite metasomatic rocks in the mining area is 183 ~ 272 Ma, which is widely distributed (Liu Guoping, 2002). The 40Ar/39Ar plateau age of sericite in gold-bearing altered rocks is 65438±067±2ma, and its isochron age is 65438±067±4ma, which represents the metallogenic age and mineralization.

4.7 deposit types

The genetic viewpoints of this deposit are mainly as follows.

The genetic type of 1) deposit is fine disseminated (Carlin type) gold deposit (Liu Guoping, 1999).

2) "Fine clastic rock type" gold deposit (Yang Dejiang, 1999). Jet rock type gold deposits (Anton, 2004).

3) epithermal deposits (Liu Guoping, 1998, 2002) occurs in intermediate and high-grade metamorphic rocks.

4) epithermal infiltration gold deposit (Wang Wenqing et al., 2000).

5) Turbidite type gold deposits (Chen Jiang, 2000) and magmatic hydrothermal type gold deposits (Min Wei, 200 1).

6) The genetic type of the deposit is syngenetic sedimentation-metamorphism-magmatic hydrothermal superimposed transformation type (sunny day, 1997).

7) Hydrothermal deposit and gold deposit transformed by metamorphic hydrothermal solution (Liu Hongxia, 2006).

refer to

Anton. 2004. Geological characteristics of Xiaotongjiapuzi gold deposit. Mining and Metallurgy of Nonferrous Metals, 20 (3): 6 ~ 8

Dai Junzhi, Wang Keyong, Yang, et al. 2006. Characteristics and metallogenic mechanism of ore-forming fluids in Xiaotongjiapuzi and Linjia gold deposits in Qingchengzi. Geological Review, Vol.52, No.6: 836 ~ 842.

Hu Tiejun. 200 1. Gold and silver mineralization, ore-controlling factors and prospecting ideas in Qingchengzi area. Geological exploration series,16 (3):187 ~191.

Liu Guoping. 2002. Discussion on metallogenic epoch of Xiaotongjiapuzi gold deposit in Liaoning Province. Geology of mineral deposits, 2 1 (1): 53 ~ 57.

Liu Guoping, Ai Yongfu. 1998. Study on rock geochemistry and metallogenic conditions of Xiaotongjiapuzi gold deposit in eastern Liaoning. Geology of the deposit,17 (4):147 ~152.

, Sun, Zhao Guangfan. 1997. Geological characteristics and ore-forming material sources of Xiaotongjiapuzi gold-silver deposit in Qingchengzi ore field. Gold,18 (12):13 ~18.

Cai. 1999. Geological characteristics and metallogenic mechanism of Xiaotongjiapuzi gold deposit in eastern Liaoning. Nonferrous metal minerals and exploration, 18 (5): 246 ~ 269.

Zhao Guangfan is from Sun Limin. 1997. Geological characteristics and genetic mechanism of Xiaotongjiapuzi gold deposit in Qingchengzi ore field. Geotechnical engineering, 6 (4): 2 12 ~ 2 17.

(Written by Xiao Li)