(1) metal deposits (spots)
Beishan area spans three ancient plates: 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 nonmetal) deposits (points) are scattered. 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 9 1 small and medium-sized deposits, through the exploration and evaluation of more than 20 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, including Gongpoquan, all the virtues Hall and Huitong Mountain. ③ Two copper-nickel deposits, represented by gourd; ④ There are 4 Pb-Zn-Ag deposits, representing Hua Niu Shan; ⑤ There are 2 rare metal deposits, representing Qiyishan; ⑥ There are four tungsten deposits, representing Hongjianbing Mountain and Yingzui Hongshan; ⑦ There are 30 iron ore deposits, including 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 three molybdenum deposits, and the representative deposits are Liusha Mountain and Huaheitan. It is worth mentioning 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 each mining area 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 reserve, most of them are geological reserves and prospective reserves. In the exploration degree of mineral reserves, the general survey level accounts for about 90%, and the exploration depth is generally less than 300m, most of which are general survey drilling holes, and there is still a large prospecting space in its depth and periphery; Second, the exploration methods are backward: the exploration of gold, copper, copper-nickel deposits basically adopts the technical methods of the 1960s and 1970s, with outdated drilling equipment, low efficiency, high cost and poor data reliability. Considering the above two aspects comprehensively, we believe that the prospecting prediction of the deep, periphery and extension of existing mineral resources should be an important content of mineral resources investigation and evaluation 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.
(2) Prospecting and pre-investigation area
In addition to the above-mentioned 93 discovered deposits, in recent three years, we have closely cooperated with the scientific research personnel of Inner Mongolia Geological Survey Institute, and through systematic field geological investigation and detailed indoor research, we have successively discovered three areas of Heping deposit and copper-molybdenum pre-investigation in Beishan, Inner Mongolia, including Bailiantu, Jinta County, Gansu Province, Ergenwula, Ejinaqi, Inner Mongolia. Chapter IV of this report will introduce these pre-investigation areas in detail.
(3) Division and main geological characteristics of metallogenic areas (belts)
According to the last round of mineral geological survey, Beishan area is divided into three grade III metallogenic belts, eight grade VI metallogenic belts and 32 grade VI metallogenic belts, metallogenic areas, ore fields or pre-survey areas. See Nie's Metallogenic Regularity and Prospecting Direction of Metal Deposits in Beishan Area (2002b) for details.
Second, Alashan region.
(A) 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. After more than half a century of geological prospecting, 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. In addition, there are more than 100 geochemical anomalies and more prospecting information that need to be further verified. The above geological characteristics show that Alashan area has great prospecting potential, which provides guidance and target area for finding large-scale deposits in the future. Among these discovered mineral deposits, metal minerals mainly include iron, gold, copper, rare metals, chromium and platinum. There are 0 large-scale deposits 1 deposit, 3 medium-sized deposits, 9 small-scale deposits, 9 ore occurrences and 2 pre-survey areas (table 1-4- 1), of which ① iron ore. ② There are 6 gold deposits (spots), and the representative gold deposits are Zhulazaga, Chagan Chulu and Hulun Bai Xi; ③ There are 2 copper polymetallic deposits (spots), which are represented by Naomuhong and Zhusileng Helehan; ④ There are 2 rare metal deposits, representing Taohuala Mountain and Qigetaobao; ⑤ The chromium deposit is located in 1, that is, Xiaosongshan; ⑥ The occurrence of platinum is 1, which is Aobao and alatan.
Although Alashan area has made a lot of prospecting achievements, compared with its neighboring areas, there are still obvious gaps in the number and scale of discovered deposits (points). 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, Inner Mongolia Land and Resources Exploration Institute and Inner Mongolia Geological Survey Institute have discovered better copper-gold mineralization zones in Zhusileng Hehan, Chagan Chulu and Bayinle respectively, which is a good example. All sections in Alashan area show great prospects for metal deposits, and hidden metal ore bodies may also be found in the periphery and depth of some production mines.
Table 1-4- 1 List of Main Metal Deposits (Points) in Alashan Area
(2) Division and main geological characteristics of metallogenic areas (belts)
Principles and basis for the division of 1.
As mentioned above, Alashan area is an important metallogenic area with iron and gold as the main components, as well as copper, rare metals, chromium and platinum. All kinds of metal deposits (spots) are mostly concentrated in a limited space, which are interrelated and form a large mineralization concentration area or zone. The preliminary research results show that this area has great metallogenic potential and good prospecting prospects in iron, gold, copper, rare metals, chromium and platinum deposits. According to the regional metallogenic conditions, metallogenic regularity and prospecting criteria, how to accurately divide the metal deposits (points) in this area is not only an urgent task for current metallogenic prediction and prospecting, but also an important means for comprehensive investigation and evaluation of mineral resources.
In order to make a better and more accurate metallogenic prediction, the principles we follow when dividing mining zones are as follows: ① The geotectonic environment in which metal deposits (points) are located is the same, and the regional crustal evolution is consistent with the metallogenic process; (2) Consistency or similarity of ore-hosting 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 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 the division of mining areas is: ① the 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 sequence of metamorphic rocks, fault structure types); (3) Geological characteristics and distribution range of different structural 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 above-mentioned principles and basis for the division of metallogenic belts (belts), and referring to the Reference Opinions on Classification and Naming of Basic Requirements for Metallogenic Prediction of Solid Minerals (Trial Draft) issued by the former Ministry of Geology and Minerals, Alashan area is regarded as the Grade III metallogenic belt of Meng Xing metallogenic belt (Grade II), and then four grade IV metallogenic areas are divided in turn. They are: ① Diebusk-Suhaitu sedimentary metamorphic iron ore belt; ② Zhamu 'ao-Bayin Nuoergong-Diebusk Au-Fe-Cu-W metallogenic belt; ③ Wuliji Fe-Cu-Au metallogenic belt; ④ Argan 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 meanings of other symbols in the figure. )
3. Basic geological characteristics of metallogenic belt
(1) Diebsg-Suhaitu sedimentary metamorphic iron ore belt (Ⅳ-1)
The metallogenic belt is located in the southeast of Alashan ⅲ metallogenic belt, and it is distributed in the northeast direction. The whole ore belt is about 250km long, about 100km wide and about 25,000 km2 in area. 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 were influenced by multi-stage tectonic-magmatic activities in the later period and were covered by Paleozoic and Mesozoic-Cenozoic sedimentary rocks, the iron deposits in these ancient metamorphic rocks were basically unaffected. 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 found in this metallogenic belt, including Diebuge, Kuanwanjing, Kelinhada, Chahan Tolgoi and Aolun brug 86 anomaly. It should be pointed out that the discovered iron ore deposits (spots) are mainly concentrated in the northern part of the ore belt. In contrast, Archean metamorphic rocks are exposed in a large area in the southern belt, and it is also promising to find sedimentary metamorphic iron deposits in the southern belt.
(2) Zhamu 'ao-Bayin Norgong-Diebushgejin-Fe-Cu-W metallogenic belt (Ⅳ-2)
The metallogenic belt is near the south side of the fault zone in the northern margin of Alashan, and it is distributed in the northeast direction. The whole ore belt is 500 kilometers long, 80 ~100 kilometers wide and covers an area of 50,000 square kilometers. 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. From Archean to Yanshanian, especially in the late Hercynian, magmatic rocks are widely distributed. The mineralization of iron, gold, copper and tungsten in the metallogenic belt is closely related to these magmatic rocks. So far, Zhulazaga large gold deposit, Kaxiutata medium-sized iron-gold-cobalt deposit, Lucaojing small iron deposit and Naomuhong small 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 iron copper gold metallogenic belt (Ⅳ-3)
The metallogenic belt is located between the Engelwusu fault and the North Alashan fault. The whole metallogenic belt is 170km long, 0.70km wide and 12000 km2 in area. The strata exposed in the metallogenic belt are mainly a set of upper Paleozoic pyroclastic rocks and normal sedimentary rocks, and the main magmatic rocks are Hercynian granite intrusive rocks. In this ore belt, Chagan Chulu and Bayangaole gold deposits or pre-exploration 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) Argan copper-gold metallogenic belt (Ⅳ-4)
The metallogenic belt is located between Engelwusu fault and Yagan fault. The whole ore belt is 1 10km long and 00km wide, with a distribution area of 5500km2. 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 acid intrusive rocks in the Middle Hercynian period, and Caledonian and Indosinian intrusive rocks are found in some areas. There are few mineral deposits in this area. At present, only Guaizihu iron deposit, Hulun Bai Xi gold deposit and Zhusileng Heierhan copper-gold deposit have been discovered. It is worth mentioning that although the porphyry copper-gold mineralization body occurs in the pre-investigation area of Zhusilenghe Khan copper-gold deposit, 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.
Three. Classification of metal deposits (points)
Metal deposits (spots) in Alashan area mainly include iron, gold, copper, rare metals, chromium, platinum, etc., which have the characteristics of diverse deposit types, relatively concentrated metallogenic age and complex host rocks. Except for 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 (occurrences) in this area, the classification schemes of different metal minerals are also quite different. Therefore, the metal minerals in this area can not be classified uniformly, but should be classified according to different minerals. The deposit types of these main minerals are briefly introduced below.
(1) iron deposit
Iron ore deposit is one of the most important metal minerals in this area. Two medium-sized iron mines and seven small-sized iron mines 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 the largest and have high grade.
1. Sedimentary metamorphic iron deposit
Sedimentary metamorphic iron ore is mainly distributed in the area from Diebule, Alashan, Zuo Qi to Chahantaoleg. The ore-forming age is pre-Great Wall Age, and iron ore occurs in Archaean amphibolite gneiss and iron-bearing quartzite of Diez Fort Formation. The representative iron deposits (spots) are Dubre, Kuanwan well, Kelinhada, Chahan Toleg and Aolun brug 86 anomaly (table 1-4- 1, table 1-4-8).
2. Skarn iron deposit
The mineralization of this type of iron ore is related to the magmatism of Hercynian gabbro, quartz diorite, granodiorite and granite. This kind of deposit is characterized by rich ore grade, many associated beneficial components and large reserves. Representative deposits (points) include Kaxiutata, Kebrle and Charasy.
Table 1-4-2 Brief Geological Characteristics of Main Metal Deposits (Points) in Alashan Area
sequential
sequential
3. Hydrothermal filling iron deposit
Mainly distributed in Alashan block, its mineralization is related to Hercynian magmatism. Representative deposits are Yantula and Lucaojing.
4. Sedimentary iron deposits
This type of deposit is characterized by small production scale and sporadic distribution, which is closely related to the spatial distribution of Carboniferous sedimentary rocks. Representative mines are Guaizi Lake and Daoyu Jiaobao.
(2) Gold deposits
Gold deposits (spots) are widely distributed in this area. The Zhulazaga gold deposits discovered in Alashan, Zuo Qi at the end of the 20th century are all occurrences or pre-exploration areas except for large scale. * * * There are 65,438 large gold deposits, 5 occurrences (including pre-survey areas) and 65,438 associated gold deposits (Kaxiutata). There are many types of gold deposits in this area, including: ① gold deposits related to shallow metamorphic clastic rocks, such as Zhulazaga gold deposit; (2) Gold deposits related to subvolcanic rocks, such as Chagan Chulu gold deposit pre-survey area; ③ Gold deposits related to skarn, such as Bayangaole and Kaxiutata; ④ Time-pulse type gold deposits, such as Hulun Bai Xi. Although the host rocks of these gold deposits are different, their mineralization is related to intermediate-acid magmatism in the late Hercynian period.
(III) Copper deposits
So far, only two copper deposits or pre-investigation areas have been discovered in this area, namely Naomuhong and Jusileng Haier Khan. The deposit types belong to skarn type and porphyry type respectively, and its mineralization is related to Hercynian intermediate-acid magmatism.
(4) Rare polymetallic deposits
Although the number of deposits (points) is small, the output scale is large, with medium-sized deposits 1, small deposits 1 and occurrences 1. Among them, Taohualashan niobium deposit is located in pre-Cambrian carbonate rocks, which is related to submarine volcanic activity. On the contrary, the mineralization of the rare metal deposit in Getaobao is related to the magmatic activity of alkaline granite, and the mineralization is mainly distributed in the contact alteration zone between alkaline granite and carbonate rock.
(5) Chromite deposit
So far, only 1 chromite deposit related to ultramafic rocks-Xiaosongshan deposit in Alashan, Zuo Qi has been discovered. Because of the low chromium content in the deposit, the deposit has no industrial value.
(vi) Platinum deposits
At present, the two discovered platinum occurrences are located near Alateng Aobao, Alashan Right Banner, and belong to placer mines. The ore bodies occur in Quaternary alluvial, diluvial and gravel layers.
See table 1-4-2 for the main geological features of the above representative metal deposits (points).