Deep Geological Characteristics and Ore Predition of Vein 175 in Linglong Gold Field in Jiaodong Area, Shandong Province

Located on the west coast of the Pacific Ocean, Jiaodong gold concentration area is one of the world's famous gold deposit areas. Its unique metallogenic environment and metallogenic background are favored by geologists of all countries, multi-level and multi-disciplinary scientific research work has been carried out in this area, and good results have been achieved. Linglong gold deposit, located 20 km northeast of Zhaoyuan, Shandong, is a quartz vein type gold deposit. Its veins are controlled by Linglong and Batouqing fault, and vein groups are developed in the area, there are 36, 48, 47, 53, 55, 108 and vein groups 175, among which vein group 175 is one of the main large vein group in Linglong Gold Mine. With the continuous exploitation and utilization of the shallow resources in Linglong Gold Mine, the amount of gold resources kept in Linglong Gold Mine has decreased sharply, and the enterprises are facing the situation of serious shortage of resources. In order to prolong the service life of mines, it is urgent to enlarge the geological reserves of gold deposits and to increase the prospecting and prospecting efforts in deep areas. In this paper are sunnarized the geological and metallogenic backgroud and geologcal characteristics of the ore vein groups 175 and ore-control factor, occurrence pattern of ore body and ore types are analyzed and metalogenic pattern described. Based on prospecting works in which ore is encountered gold ore reserve 192.44×104t (332+333) and gold metal reserve 8.5t are predicted by geologic block method bellow -800m level beteen line 11-101.


Introduction
The Linglong gold mining area is located 20 km north of Zhaoyuan, Shandong province, Its geographical coordinates: E120°27′08″-E120°33′55″, N37°26′ 07″-N37°29′21″ (1). Linglong gold deposit belongs to Quartz Vein type gold deposit. Vein Group is developed in the gold deposit area. Ore vein group 175 is one of the main large vein group in Linglong gold deposit. The No. 175 pulse group is close to the broken head-qing fault, which is mainly composed of No. 176, No. 175 and No. 47 pulse. The elevation above-200m of the Vein Group is controlled by prospecting engineering, and the research degree is relatively high.
With the continuous exploitation and utilization of the shallow resources in Linglong Gold Mine, the amount of gold resources kept in Linglong Gold Mine has decreased sharply, and the enterprises are facing the situation of serious shortage of resources. In order to prolong the service life of mines, it is urgent to enlarge the geological reserves of gold deposits and to increase the prospecting and prospecting efforts in deep areas [1][2][3][4]. From December 2005 to December 2008, Shandong Zhengyuan Geological Resources Exploration Co., Ltd. carried out the exploration work of replacing resources in vein group No. 175 in this area. The total amount of drilling work was 22482.6 m, the amount of tunnel work was 5894.06m, and the Exploration Fund was 31598.8 million yuan; In this paper, the systematic drilling engineering control is carried out for the 175th VEIN group drilling project under the elevation-400m, the gold resources reserves are estimated by using the geological block method, and the amount of (333) gold ore is 428.06 ~ 10 4 t, and the amount of metal is 24.8t.
On the basis of the field work in 2009, the geological characteristics of the deep part of Vein Group 175 (below-400m elevation) are deeply analyzed, and the vertical zoning regularity of gold mineralization in the deep part of Vein Group 175 is summarized, the deep metallogenic prognosis of the 11-101 exploration line of vein group 175 below -800m level is attempted.

Geological Setting of Mineralization
Linglong gold deposit is located at the eastern end of Zhaoye-Gold-Belt in Shandong Province. Its mineralization is controlled by Zhaoping Fault Zone. The main outcrops in the area are Guogezhuang formation of Jiaodong group and Piedmont formation of quaternary. The Mesozoic magmatism in the area is frequent and intense, which can be divided into three stages: (1)   The strike of the Linglong fault is NE25°-35°, the dip of the south segment is SE, the dip of the north segment is NW, and the dip angle is 65°-85°. The length of the fault is about 4.6 km and the width is 50-150m. It has silicification, potassium, chlorite and sericite-quartzization. The shallow part of the fault zone is a long-term active fault which existed before mineralization and continued to be active after mineralization. In the deep part of Linglong fault zone, potassium and sericite alteration are found, and pyrite is found in local area. The distribution of pyrite is scattered and fine net vein, and the gold grade (Au) is between 0.30×10 -6 and 1.05×10 -6 , up to 2.5×10 -6 .
The Potouqing fault is characterized by NE60-70° strike, trends SE, dip angle 40°, width 250-340m and width up to 700m, the tectonite group is composed of cataclastic granite, granitic cataclasite, cataclastic rock, tectonic Breccia, mylonite and fault gouge. The tectonite has undergone hydrothermal alteration or mineralization to varying degrees and belongs to rock-controlling and ore-controlling structures [5]. The Fault Gouge developed in the footwall of the fracture zone and is the main fracture surface. There are sericitization, potash, silicification, carbonation and chlorite alteration in the country rocks, and the mineralization alteration includes pyrite, lead-zinc, chalcopyrite, gold and silver mineralization. In general, the fracture zone is wider, the rock is strong, the alteration is strong, the footwall is strong, the mineralization is strong, the gold ore body is located in footwall. The No. 175 Vein group in Linglong gold Mine is close to the Poutouqing fault.

Geological Characteristics of Vein Group 175
In this paper, the vertical zoning of gold mineralization in the deep part of Vein Group 175 (below-400m elevation) is summarized through deep analysis of geological characteristics and comparative study of geological prospecting data in the past, the occurrence characteristics of deep gold orebody can be obtained (2).
(1) Secondary Veins present laterally on the side of the main vein. The Linglong gold field is thought to be composed of structural alteration and mineralization zones of different directions and stages [5]. The alteration zoning of the deposit is the product of tectonically controlled hydrothermal diagenesis and mineralization [6]. Figure  2 shows Obliquity law is a common geological phenomenon in vein-type gold deposits, that is, the vein appears obliquity 3 2 ηγ lDz 3 2 ηγ lL 3 2 ηγ lJ 1 5 µγ ωF 2 5 gXηγ and pinch-out in strike and dip, and the ore body accumulates in stages in the vein. The scale, shape and occurrence of ore veins and orebodies are strictly controlled by fault structures, which often provide favorable places for gold mineralization. According to the geological data of the mining area, the fault structures in this area extend slowly in strike, and the gold mineralization is enriched in dip. There are many orebodies in the exposed veins, all of which have NW dip, dip angle ranging from 45° to 60°, and 2m to 30 m interval extension (table 1). (4) The ore body has vertical zonation. According to the analysis of geological data, the quartz vein and the transitional vein of Linglong gold deposit have similar vertical zoning of mineralization belt, but the occurrence level of the enrichment belt of these two types of veins is slightly different from that of the altered lithologic vein. The actual production data show that the mineralization is strong and the ore body is rich in the range of-200m~-320m, the mineralization is weak and the gold ore body is weak in the range of-320m~-420m, the mineralization is strong and the ore body is rich in the range of-420m~-470m. In the range of-470 ~-520m elevation, the mineralization is weak and the gold ore body is relatively weak, and in the range of-520 ~-570m elevation, the mineralization is strong and the ore body is rich. That is to say, the weak mineralization belt and the rich belt of orebody are vertical zonation. The analytical results of the samples described in Table 2 3 show that the veins become thicker and lower in grade when they meet. But the ore bodies are developed near the junction, which is the favorable area for mineralization.

Orebody Characteristics
There

Mineral Composition Characteristics
(1) Mineral composition of ore. The gold ores are mainly pyrite quartz veins and pyrite sericite quartzite. The metallic minerals in the gold ores are mainly pyrite, Chalcopyrite, Galena and sphalerite, and occasionally magnetite and tetrahedrite. The nonmetallic minerals are mainly quartz, plagioclase, potash feldspar and sericite, second for Calcite, biotite, chlorite, and a small amount of hornblende, muscovite, carbonate minerals, apatite, sphene and so on. Figure 3 is a photomicrograph of the ore. There are metallic minerals native gold ( Figure 3A), silver gold, pyrite ( Figure 3B), chalcopyrite ( Figure 3C), Galena, sphalerite, and occasionally magnetite and tetrahedrite Non-metallic minerals are mainly quartz, plagioclase, potash feldspar (Figure 3d), sericite, calcite, biotite, chlorite, and a small amount of Hornblende, Muscovite, carbonate minerals, apatite, sphene [7]. (2) Chemical composition of ore. Table 4 shows the results of chemical multi-element analysis of gold ores. The results show that the main useful components of Gold Ores are Au, AG and S, with mean values of 4.185×10 -6 , 7.95×10 -6 and 3.60×10 -2 respectively. Table 4. Multi-elements analysis of ore.
ω (Au)/10 -6 ω (Ag)/10 -6 ω (Cu)/10 -2 ω (Pb)/10 -2 ω (Zn)/10 -2 ω (Sn)/10 -6 ω (As)/10 -6 ω (Sb)/10 -6 ω (Bi)/10 -6 Pyrite Quartz Vein 3.  (3) Beneficial and associated ingredients. AU is the main beneficial component in the ore, its content (mass fraction) varies widely, (Au) ranges from 1×10 -6 to 46.18×10 -6 , and the single sample is the highest (Au) = 46.18×10 -6 . There is no regularity in the variation of gold grade along strike and dip, the gold grade is generally related to the ore type and alteration degree of the ore body. AG is one of the main beneficial associated components in the ore. Its (Ag) values range from 1.20×10 -6 to 22.30×10 -6 with an average (Au)=4.95×10 -6 . The content S of is between 0.67% and 5.78%, with an average of 2.31%. the S value is related to ore type and mineralization degree. (4) Mineralization stage. According to the field observation, laboratory identification and the division of regional metallogenic stages, the mineralization stage is divided into four stages: pyrite-quartz stage, gold-quartz fine-grained pyrite stage, gold-silver polymetallic sulfide stage, gold carbonate stage. According to the data of geological and mineral exploration, there are two mineralization types of quartz vein type and altered rock type in vein group No. 175, which are obviously symmetrical zonal distribution. In most cases, quartz vein type gold ore or pyrite quartz vein type gold ore is commonly found in the vein body center. According to the mining data of Linglong Gold Mine, the opalescent quartz and pyrite particles in the vein have obvious crushing structure, many cracks and very low gold content; polymetallic sulphides occur as medium-fine grained, disseminated, veined or interspersed in cracks of coarse grained pyrite, and their gold-bearing properties are good.

Deep Orebody Prediction
The No. 175 Vein Group of Linglong Gold Mine is located in the West side and lower wall of the Botouqing fault, and controlled by the secondary faults of the Poutouqing fault. The fracture direction is 55°±, the dip angle is between 40° and 50°, and the trend of dip to depth is 30°±. The footwall of the fault zone is characterized by secondary and low-sequence faults and fractures, which is the hosting space of quartz vein type gold veins. The vein group is generally distributed and varied with the main compression-torsion structural rock zone, and the dip is NW, NNW and NE.
(1) Different types of fault systems provide different physical chemistry environments for hydrothermal activity and gold enrichment, resulting in different types of ore veins. Linglong gold deposit is a typical vein-type deposit. Most of the veins are gold-bearing quartz veins, sulfide-bearing quartz veins, sulfide-bearing quartz veinlets, etc. In the tectonic activity, the intersection area provides space for the gold mineral enrichment, the gold-bearing hydrothermal solution repeatedly precipitates the enrichment to form the gold ore body. According to the mining means of production, there are many industrial ore bodies near the intersection of the two veins in Linglong mining area, which are large in scale and high in grade (Au) up to 422.87×10 -6 . The ore veins extend to the deep with the dip angle from 40°to 80°, and the possibility of the intersection of the two veins is very high. Therefore, the near junction of the two deep veins is of great significance for ore prospecting. (2) the existing geological prospecting data show that the ore bodies in the same vein generally occur at intervals of 200-300m and their scale is generally 200-500×0.80-6.20 m, and the elevation of the ore bodies is -1000m±, most of the ore veins are shallow in depth and extend to deep unclosed. Based on this, it can be predicted that the control elevation of the orebody is -1600m or deeper, and the potential of deep prospecting is great [8][9][10][11]. Based on the field work in 2009, the geological characteristics of the deep part (below-400m) of vein group No. 175 in Linglong gold mining area are analyzed, the deep prospecting of vein group No. 175 in Linglong gold mining area is predicted by using the geological block method and the gold ore resource (332 + 333) is 192.44×10 4 t below the elevation of 11-101 exploration line-800m of vein group No. 175 in Linglong gold mining area, 8.5t of metal.

Conclusion
(1) Affected by the structure of Potouqing fault, the veins and deep gold deposits in linglong mining area have the law of ne extension and lateral declination. The deep ore type is mainly altered rock type, and the second is quartz vein, and the thickness grade of the veins decreases linearly.
(2) Most of the deep ore veins are in the shape of "Y" intersection, which provides space for the enrichment of gold minerals. The gold-bearing hydrothermal solution is repeatedly precipitated and enriched, resulting in high grade.
(3) The deep orebody of No. 175 vein group has vertical zonation, the orebody can extend to-1600m or deeper, and the deep orebody has huge resource potential.