I. Beishan area

(I) Metal deposits (spots)

Beishan area spans three ancient plates, namely Siberia, Kazakhstan-Beishan and Tarim. The structure in the area is complex, the strata in each era are well developed, there are many types of magmatic rocks, metamorphic rocks are widely exposed, the metallogenic geological environment is superior and metal (or nonmetallic) deposits (spots) are scattered all over. According to the available information and data, the metal minerals in Beishan area are mainly gold, iron and copper, followed by polymetallic minerals such as lead-zinc-silver, rare metals, tungsten and molybdenum. Non-metallic minerals are mainly fluorite and coal, followed by phosphorus and magnesite. Since the founding of New China, geologists have discovered 93 metal deposits, including 2 large-scale deposits and 91 small and medium-sized deposits, through the exploration and evaluation of more than 2 kinds of minerals such as gold, iron, copper, copper-nickel, tungsten, molybdenum, lead-zinc-silver, rare metals, vanadium, phosphorus, coal, fluorite and magnesite. Statistics show that minerals with important industrial value mainly include: ① 29 gold deposits, among which Xiaoxigong, Nanjinshan, Mazhuangshan, Jinwozi and Zhaobishan are representative deposits; ② There are 3 copper deposits, and the representative deposits are Gongpoquan, Baishantang and Huitongshan; ③ There are 2 copper-nickel deposits, with gourd as the representative deposit; ④ There are 4 Pb-Zn-Ag deposits, and the representative deposit is Hua Niu Shan; ⑤ There are 2 rare metal deposits, and the representative deposit is Qiyishan; ⑥ There are 4 tungsten deposits, and the representative deposits are Hongjianbing Mountain and Yingzui Hongshan; ⑦ There are 3 iron ore deposits, and the representative deposits are Heiying Mountain, Langwa Mountain, Yuejin Mountain and Jasper Mountain; ⑧ There are 2 vanadium-phosphorus-uranium deposits, and the representative deposit is Fangshan Pass; 9 There are 3 molybdenum deposits, and the representative deposits are Liusha Mountain and Huaheitan. It should be mentioned that although this area has made gratifying achievements in various mineral exploration, there are still many problems, mainly in two aspects. First, the exploration degree of various mineral areas is low: most of the collected geological reports are general survey geological reports. Judging from the level of metal reserves of various metal deposits, except for a small part of industrial reserves, most of them are geological reserves and prospective reserves. In the exploration degree of mineral reserves, the general survey level accounts for about 9%, and the exploration depth is generally less than 3m, most of which are general survey boreholes, and there is still a large prospecting space in its deep and periphery; Second, the exploration methods are backward: the exploration of gold, copper and copper-nickel deposits basically adopts the technical methods of the 196s or 197s, and the drilling equipment is outdated, inefficient, costly and the data reliability is poor. Considering the above two aspects, we think that the prospecting prediction of the deep part of the existing mineral resources and its periphery and extension should be an important part of the investigation and evaluation of mineral resources in this area; At the same time, it is also the key to achieve a breakthrough in prospecting in this area in a short time.

(II) Prospecting pre-survey areas

In addition to the above-mentioned 93 discovered mineral sites, in recent three years, we have closely cooperated with the researchers of Inner Mongolia Geological Survey Institute, and through systematic field geological survey and detailed indoor research work, we have successively discovered three pre-survey areas of Heping deposit, copper and molybdenum in Beishan area of Inner Mongolia and Beishan area of Gansu, among which Bailiantu, Jinta County, Gansu Province, and the pre-survey area of molybdenum and copper with excellent prospecting prospects. In the fourth chapter of this report, these pre-investigation areas will be introduced in detail.

(III) Division of Metallogenic Zones (Zones) and Main Geological Features

According to the last round of mineral geological survey, Beishan area was divided into 3 Grade III metallogenic zones, 8 Grade VI metallogenic zones, and 22b Grade V metallogenic zones, metallogenic zones, ore fields or pre-survey areas. See Nie Fengjun's "Metallogenic Rules and Prospecting Direction of Metal Deposits in Beishan Area" for the basis and main features of the division of metallogenic zones.

2. Alashan region

(1) Regional mineral distribution characteristics

Alashan region is located at the intersection of Tarim and North China platform and in the middle of Tianshan-Xing 'an metallogenic domain. Through more than half a century's geological prospecting work, a large number of mineral deposits have been discovered in Alashan area, mainly including coal, salt lake, mirabilite, iron, gold, phosphorus, limestone, gypsum, bentonite, talc and decorative granite. Among them, there are 2 large, 5 medium, 8 small and dozens of occurrences. In addition, more than 1 geochemical anomalies and more prospecting information need to be further verified. The above geological characteristics show that there is great prospecting potential in Alashan area, which provides guidance and target for finding large-scale deposits in the future. Among these discovered mineral deposits, the metal minerals are mainly iron, gold, copper, rare metals, chromium and platinum, and there are 1 large deposit, 3 medium-sized deposits, 9 small deposits, 9 ore occurrences and 2 pre-survey areas (Table 1-4-1), among which ① there are 12 iron deposits (points), and the representative deposits are Diebsger and Kaxiuta. ② There are 6 gold deposits (spots), and the representative gold deposits are Zhulazaga, Chagan Chulu and Hulun Xibai; ③ There are 2 copper polymetallic deposits (spots), and the representative deposits (spots) are Naomuhong and Zhusileng Helhan; ④ There are 2 rare metal deposits, and the representative deposits are Taohuala Mountain and Qigetaobao; ⑤ One chrome ore spot, namely Xiaosongshan; ⑥ 1 platinum mine, namely Aobao, alatan.

Although a lot of achievements have been made in prospecting in Alashan area, there are obvious gaps in the number and scale of deposits (spots) found compared with neighboring areas. Generally speaking, the metallogenic conditions in this area are superior and the prospecting potential is huge, but the degree of work is low. In recent years, the Inner Mongolia Land and Resources Exploration Institute and the Inner Mongolia Geological Survey Institute have discovered better copper and gold mineralization zones in Zhusileng Helhan, Chagan Chulu and Bayinle respectively, which is a good example. All sections in Alashan area show great prospecting prospects for metal deposits, and it is also possible to find hidden metal ore bodies in the periphery and depth of some production mines.

table 1-4-1 list of main metal deposits (spots) in Alashan area

(ii) division of metallogenic areas (belts) and main geological characteristics

1. Principles and basis of division

As mentioned above, Alashan area is an important metallogenic area dominated by iron and gold, with copper, rare metals, chromium and platinum. All kinds of metal deposits (spots) are mostly concentrated in a limited spatial range, and they are connected with each other to form a larger mineralization concentration area or zone. The preliminary research results show that this area has great metallogenic potential and good prospecting prospect in terms of iron and gold deposits, as well as copper, rare metals, chromium and platinum deposits. According to the regional metallogenic conditions, metallogenic regularity and prospecting criteria, how to divide the metal deposits (spots) in this area accurately is not only an urgent task for current metallogenic prediction and prospecting, but also an important means for comprehensive mineral resources investigation and evaluation.

in order to make a better and more accurate metallogenic prediction, we mainly follow the following principles when dividing into mining zones: ① the geotectonic environment in which metal deposits (points) are located is the same, and the regional crustal evolution and mineralization process are consistent; (2) Consistency or similarity of host rocks (sedimentary rocks, metamorphic rocks or magmatic rocks) in time and space distribution; (3) Consistency of internal relations between regional structures and ore-controlling structures; ④ Consistency of internal relations between regional magmatism and mineralization; ⑤ Unity, similarity or consistency between the regional metallogenic system and the metallogenic process of a single metal deposit. In addition, the main basis for dividing into mining zones is as follows: ① main geological characteristics and distribution range of metal deposits (points); ② Main ore-controlling factors (stratigraphic sequence, sedimentary rock formation, development degree of magmatic rocks, distribution range of volcanic rocks, metamorphic order of metamorphic rocks and fault structure type); ③ Geological characteristics and distribution range of different tectonic units and their relationship with metal deposits (points); ④ Geophysical field, geochemical field and remote sensing image characteristics and their spatial correspondence with metal deposits (points).

2. Division of metallogenic belt (area)

According to the division principle and basis of the above-mentioned metallogenic belt (area), and according to the reference opinion of the former Ministry of Geology and Mineral Resources on the classification and naming of the Basic Requirements for Metallogenic Prediction of Solid Minerals (Trial Draft), Alashan area is regarded as a grade III metallogenic belt of Xingmeng metallogenic belt (grade II), and then four grade IV metallogenic areas can be divided in turn. They are: ① Diebsg-Suhaitu sedimentary metamorphic iron ore belt; ② Zhamuao-Bayin Norgong-Diebusgejin-Fe-Cu-W metallogenic belt; ③ Wuliji Fe-Cu-Au metallogenic belt; ④ Yagan copper-gold metallogenic belt (Figure 1-4-1).

Figure 1-4-1 Schematic diagram of metallogenic belt division in Alashan area

(see Figure 1-3-2 for the meaning of other symbols in the figure)

3. Basic geological characteristics of metallogenic belt

(1) Diebsg-Suhaitu sedimentary metamorphic iron ore belt (Ⅳ-1)

This metallogenic belt is located in the southeast of Alashan Grade III metallogenic belt. In view of the fact that the sedimentary metamorphic iron deposits in this ore belt are all produced in Archean-Proterozoic medium-deep metamorphic rocks, the distribution range of this ore belt is consistent with the exposed range of these medium-deep metamorphic rocks. These Archean-Proterozoic medium-deep metamorphic rocks are also the oldest rocks in Alashan block, which constitute the basement of Alashan block. Although all kinds of rock masses (strata) in this area have been affected by multi-stage tectonic-magmatic activities in the late stage and covered by Paleozoic and Mesozoic-Cenozoic sedimentary rocks, these iron deposits in ancient metamorphic rocks have basically not been significantly affected. Up to now, a number of small and medium-sized iron deposits and a large number of iron ore spots and abnormal zones have been discovered in this metallogenic belt, including Diebusge, Kuanwan Well, Kelinhada, Chahantaolegai and Aolun brug 86 anomaly. It should be pointed out that the discovered iron ore deposits (occurrences) are mainly concentrated in the northern part of the ore belt. In contrast, there are Archean metamorphic rocks exposed in a large area in the southern belt, so it is also promising to find sedimentary metamorphic iron deposits in the southern belt.

(2) Zhamu 'ao-Bayin Norgong-Diebusgejin-Fe-Cu-W metallogenic belt (Ⅳ-2)

This metallogenic belt is close to the south side of the fault zone on the northern margin of Alashan, and it is distributed in the northeast. The whole ore belt is 5km long, 8-1 km wide and covers an area of 5, km2. The ore belt is located at the edge of Alashan block, and the exposed strata include Archean-Proterozoic medium-deep metamorphic rocks, Mesoproterozoic shallow metamorphic clastic rocks, Paleozoic and Mesozoic-Cenozoic volcanic-sedimentary rocks. Magmatic activities are very frequent in this area, and magmatic rocks are widely distributed from Archean to Yanshanian, especially in the late Hercynian. Most of the mineralization of iron, gold, copper and tungsten in the metallogenic belt is closely related to these magmatic rocks. So far, Zhulazaga large-scale gold deposit, Kaxiutata medium-sized iron-gold-cobalt deposit, Lucaojing small-scale iron deposit and Naomuhong small-scale copper deposit, as well as some occurrences and mineralization points of iron, gold, copper and tungsten have been discovered in this metallogenic belt. Because the metallogenic belt is located on the continental margin of Alashan block, multi-stage tectonic-magmatic activities have created its superior metallogenic environment. Although many iron, gold, copper and tungsten deposits (spots) have been discovered, compared with the distribution range of this belt, the prospecting potential is still huge, and it is the first choice for prospecting breakthrough.

(3) Wuliji Fe-Cu-Au metallogenic belt (Ⅳ-3)

This metallogenic belt is located between the Engelwusu fault and the northern Alashan fault zone, and the whole metallogenic belt is 17km long, 5-7 km wide and covers an area of 12, km2. The strata exposed in the metallogenic belt are mainly a set of pyroclastic rocks and normal sedimentary rocks in the Upper Paleozoic, and the main magmatic rocks are Hercynian granite intrusive rocks. In this ore belt, Chagan Chulu and Bayangaole gold deposits or pre-survey areas, as well as some copper, iron and copper deposits (mineralization) have been discovered. Although no metal deposit with industrial value has been found in this ore belt so far, there is great potential to find porphyry copper-gold deposits related to island arc in this area because of its unique tectonic environment.

(4) Yagan copper-gold metallogenic belt (Ⅳ-4)

This metallogenic belt is located between Engelwusu fault and Yagan fault, with a total length of 11km, a width of 3-5km and a distribution area of 55km2. The main strata exposed in the metallogenic belt are carbonate-clastic sedimentary rocks of Upper Paleozoic and a small amount of Proterozoic sedimentary rocks. Magmatic rocks are mainly intermediate Hercynian acid intrusive rocks, and Caledonian and Indosinian intrusive rocks are found in some areas. There are few deposits (spots) in this area. So far, only Guaizihu iron ore spot, Hulun Xibai gold spot and Zhusileng Heierhan copper-gold prospecting area have been found. It is worth mentioning that, although porphyry copper-gold mineralized bodies are produced in the pre-survey area of Helhan copper-gold deposit in Zhusileng, due to the limited workload, little is known about its mineralization characteristics and ore-controlling factors. It is promising to increase the investment in geological work in this pre-survey area and achieve a breakthrough in prospecting.

iii. Classification of metal deposits (spots)

The metal deposits (spots) in Alashan area are mainly composed of iron, gold, copper, rare metals, chromium and platinum, and are characterized by various types of deposits, relatively concentrated metallogenic age and complex host rocks. Except for sedimentary and sedimentary metamorphic iron ore and placer platinum ore, most metal deposits (spots) have close temporal and spatial distribution relationship with Hercynian magmatic rocks, suggesting the genetic relationship between Hercynian tectonic-magmatic activity and metal mineralization. In view of the low research level of metal deposits (spots) in this area, there are also great differences in the classification schemes of different metal minerals. Therefore, it is not possible to classify the metal minerals in this area in a unified way, but to classify the deposits according to different minerals. The deposit types of these major minerals are briefly introduced below.

(1) Iron ore deposits

Iron ore deposits are one of the most important metal minerals in this area, and 2 medium-sized iron ore deposits and 7 small-sized iron ore deposits have been discovered (Table 1-4-1). According to the genetic types, it can be divided into four types: sedimentary metamorphic type, skarn type, hydrothermal filling type and sedimentary type, among which sedimentary metamorphic iron deposits and skarn iron deposits are characterized by the largest scale and high grade.

1. Sedimentary metamorphic iron deposits

Sedimentary metamorphic iron deposits are mainly distributed in the area from Diebusge to Chahantaolege in Alashan Zuoqi. The ore-forming age is pre-Great Wall Age, and the iron deposits occur in amphibolite gneiss and iron-bearing quartzite of Archean Diebsge Formation. The representative iron deposits (points) are Diebsge, Kuanwanjing, Kelinhada, Chahantaolege and Aolun brug 86 anomaly (Table 1-4-1, Table 1-4-2).

2. Skarn-type iron deposits

The mineralization of this type of iron deposits is related to the Hercynian gabbro, quartz diorite, granodiorite and granite magmatic activities. This type of deposit is characterized by rich ore grade, many associated beneficial components and large reserves. Representative mineral deposits (occurrences) include Kaxiutata, Kebrle and Charasy.

table 1-4-2 brief geological characteristics of main metal deposits (spots) in Alashan area

continuation table

3. Hydrothermal-filled iron deposits

are mainly distributed in Alashan block, and their mineralization is related to Hercynian magmatism. Representative ore deposits are Yantula and Lucaojing.

4. Sedimentary iron deposit

This type of deposit is characterized by small scale and sporadic distribution, and has a close spatial distribution relationship with Carboniferous sedimentary rocks. Representative mines are Guaizi Lake and Daoyuji Aobao.

(II) Gold deposits

Gold deposits (spots) are widely distributed in this area, except for the large-scale Zhulazaga gold deposit discovered in Alashan Zuoqi at the end of the 2th century.