Exploration and study on large-scale high-grade rutile deposits in ultra-high pressure metamorphic belt in northern Jiangsu Province

(Jiangsu Geological Survey and Research Institute, Nanjing 2 100 18)

Abstract: There are more than 2000 kinds of eclogites distributed in the ultra-high pressure metamorphic belt in northern Jiangsu, and rutile has superior metallogenic conditions. During the work of the national land and resources survey project, a large number of eclogites are counted as ore-bearing, and it is considered that the regional resources have great potential and the prospecting prospects are divided. On this basis, large and super-large deposits 1 were found, and single ore body 1 was found, with a grade as high as 3.94%. In terms of prospecting theory, the project has made important breakthroughs in the formation and evolution process of ore deposits and prospecting criteria; In terms of prospecting methods, innovative use of high-precision magnetic survey for eclogite-type rutile ore exploration and innovative use of hand-cranked twist drill for solid mineral exploration in shallow coverage area provide new technical methods for related fields.

Key words: rutile deposit; Big; High grade; Explore; Prospecting theory; Exploration methods; Northern Suzhou

With the approval of Jiangsu Geological Survey and Research Institute, the investigation and evaluation of rutile ore in ultra-high pressure metamorphic belt in northern Jiangsu has been included in the land and resources investigation project "Regional Potential Evaluation of Non-metallic Resources in Southeast Coast" (2000 ~ 200 1) and "Comprehensive Evaluation of Non-metallic Resources in Southeast Coast" (2002 ~ 2004). This paper is one of the results of investigation and evaluation of rutile ore in ultra-high pressure metamorphic belt in northern Jiangsu Province.

1 project background

1. 1 location advantage

There is a central ultrahigh-pressure metamorphic belt in central China, which runs from Kunlun in the west, Qilian, Qinling and Dabie in the east, and continues to extend eastward to Sulu area due to the Tanlu fault.

The central ultrahigh pressure metamorphic belt plays a very important role in China's geoscience research and prospecting. There is a special ultrahigh-pressure metamorphic rock-eclogite in this ultrahigh-pressure metamorphic belt, which is the parent rock of rutile, so this belt is also an important rutile metallogenic belt in China.

The UHP metamorphic belt in northern Jiangsu is located in the middle of the UHP metamorphic belt east of the Tanlu fault, and the first scientific drilling in Chinese mainland was carried out in Maobei, East China Sea.

1.2 Superior metallogenic geological conditions

The UHP metamorphic belt in northern Jiangsu is generally distributed in the northeast direction, with a length of about 140km and a width of about 90km. There are more than 2000 eclogites formed by ultrahigh pressure metamorphism in this area, and eclogites generally contain a certain amount of rutile. With the difference of rock mass, lithofacies and lithology, the rutile content is also different. According to statistics, nearly 40% eclogite can be enriched into a complete ore body. At present, many eclogite rutile deposits (spots) have been discovered, and only three large-super large deposits have been found. Therefore, this area has broad prospecting prospects and is expected to become an important titanium resource base in China.

1.3 has a broad market prospect.

1.3. 1 rutile is a strategic resource.

Titanium is an important strategic resource in the world. Titanium is widely used in military and civilian industries such as aerospace, metallurgy, chemical industry, ocean, electric power, medicine, superconductivity, submarine and building materials because of its small specific gravity, high strength, high temperature resistance, low temperature resistance and corrosion resistance. Its world consumption is growing steadily at the rate of 3% per year. However, there are few titanium-bearing minerals with industrial value in nature, mainly ilmenite and rutile.

In 2004, the global titanium dioxide production capacity was 4.5 million tons, and the chlorination process with rutile as raw material accounted for 56% ~ 57%, so the demand for rutile was huge. According to authoritative market analysis, from 2005 to 20 10, the global titanium dioxide market demand will increase at an average rate of 2% ~ 3%, and the domestic market demand will increase at an average rate of 8% ~ 10%. However, the annual output of rutile concentrate in China can only meet the market demand of about 20%, and about 80% depends on imports. Demand exceeds supply, which leads to the continuous increase in the price of rutile concentrate. Rutile, as one of the raw materials for welding electrodes, has a large market capacity. Taizhou welding rod factory in Jiangsu province alone needs more than 4000 tons every year.

1.3.2 Rutile is an efficient resource.

Although the proven resources and market consumption of rutile at home and abroad are still not as good as that of ilmenite, its high economic benefit is one of its obvious market advantages compared with ilmenite: the content of TiO2 in rutile is much higher than that of ilmenite, and its composition is simple and easy to handle, which is conducive to improving production efficiency. If garnet and omphacite are comprehensively utilized, the economic benefit of eclogite rutile can be increased by 12 times.

1.3.3 Rutile is an environment-friendly resource.

Compared with ilmenite, another market advantage of rutile is environmental protection: ilmenite synthesis 1 ton titanium oxide produces about 0.7 tons of waste, while rutile direct chlorination production 1 ton titanium oxide only produces about 0.2 tons of waste. Therefore, based on the consideration of environmental protection and improving economic benefits, rutile resources have received more attention and demand in industry. The concentrate of eclogite rutile ore contains almost no uranium and thorium, which is more conducive to environmental protection.

1.4 Historical Enlightenment

The prospecting history of rutile can be roughly divided into three stages.

Rutile placer exploration: from the end of 1950s to the beginning of 1960s, placers (spots) such as Ahu, Jiangzhuang, Alkali Field and Qinglong Mountain in Donghai County in xinyi city were discovered successively, which laid a certain foundation for the later primary ore exploration.

Rutile primary ore exploration: from the end of 1980s to the middle of 1990s, primary ore deposits (spots) such as Maobei, Chizhuang, Land Rover and Qinglong Mountain in Donghai County were discovered. There are high-grade sections, but high-grade rich ore bodies cannot be delineated;

Exploration of rutile primary rich ore:1999 ~ at the beginning of 2000, Canadian RioTinto multinational company (accounting for 40% of the world titanium resources) was the main body, and our cooperation failed.

In view of the serious coverage of this area, how to make a new breakthrough in rutile exploration. The traditional methods and means of mineral exploration have been seriously challenged, which requires us to think deeply, explore and seek new ways in order to make new breakthroughs in large-scale and rich primary rutile exploration.

2 technical concept

The overall technical route determined by the project is as follows:

Guided by surface geological survey (1: 1000, 1: 5000); Using advanced and effective geophysical means, flexible hand twist drill, combined with rutile-overburden mark, an important prospecting indicator, to find and track ore-bearing eclogite bodies; Finally, through trench exploration, drilling sampling and testing, the ore body is controlled and delineated, and the resources are estimated.

This exploration idea has three advantages: shortening the prospecting period, improving the prospecting rate of the project and saving the exploration cost.

3 scientific and technological achievements and innovation

3. 1 Main scientific and technological achievements

3. 1. 1 exploration evaluation results

Through the project work, eight rutile ore bodies (XRU 1 ~ XRU8) have been circled in the small coke eclogite. Six rutile ore bodies (HRU 1 ~ HRU6) are delineated in the eclogite of Hu Hao. At the same time, the resources of Jiao Xiao and Hu Hao mining areas were estimated (table 1), and 1 large deposit (Jiao Xiao) and extra-large deposit (Hu Hao) were submitted.

Table 1 Estimation Results of Rutile Titanium Dioxide Resource Unit: 10,000 tons

It is worth mentioning that a rutile-rich ore body has been delineated in the XRu2 ore body of Xiaojiao. The lower limit of rutile TiO2 content is 3.5%, and its average grade is as high as 3.94%. It is estimated that the resources of 333 are 5 1.500 tons, and the resources of 334 1 are 1.780 tons.

3. 1.2 Regional eclogite ore-bearing statistical results

Table 2 statistics the rutile TiO2 phase analysis results of eclogite samples with different structures in this area and two known mining areas. It can be seen from Table 2 that the content of rutile TiO _ 2 in eclogite in (1) area meets the requirements of industrial grade (> 1.5%), in which the content of rutile TiO _ 2 is enriched in ore (> 3.5%), accounting for 3.0 1%, indicating that eclogite in this area has a good content as a whole. (2) The ore-bearing property of massive eclogite is obviously better than gneiss and banded eclogite, indicating that deformation-retrogression after eclogite formation has obvious influence on its ore-bearing property, that is, deformation-retrogression reduces its rutile TiO2 _ 2 grade, and the stronger the metamorphism, the worse the ore-bearing property of eclogite. (3) The statistical situation of this area is very close to that of Maobei-Ma Jiang mining area, which proves that it is a super-large eclogite rutile deposit. This shows that among many eclogite bodies in this area, as long as the rock mass has a certain scale and the rocks are mainly massive eclogite, it is very likely that there will be eclogite-type rutile deposits with corresponding scale. (4) The eclogite in Jiao Xiao mining area is mainly massive eclogite, and the rest is less. The eclogite in massive eclogite is only 30. 1 1%, indicating that this area has rich ore potential.

Table 2 Statistical table of rutile titanium dioxide content in eclogite in northern Jiangsu Province

3. 1.3 Evaluation results of regional resource potential

The ultra-high pressure metamorphic belt in northern Jiangsu (Figure 1) selectively delineates five V-level metallogenic prospects, which are divided into three grades: A, B and C according to the prospecting prospects. The basic characteristics of each metallogenic prospect are shown in Table 3.

Table 3 List of basic characteristics of rutile metallogenic prospect area

Figure 1 Schematic diagram of the distribution of eclogite bodies and rutile prospect areas in northern Jiangsu.

3.2 Innovation

3.2. 1 Explore theoretical innovation

3.2. Formation and evolution of1.1rutile deposit

Eclogite is not only the host rock of rutile ore, but also the ore-forming parent rock. Based on the study of the chemical composition of various rocks in this area, it is considered that the metamorphic protolith of eclogite is basic rock, which is rich in beneficial components such as TiO2, which provides a material source for the formation of rutile ore. Rutile deposit was formed by metamorphism under high temperature and ultra-high pressure. Combined with the tectonic position of this area, it should be the result of collision and subduction between North China plate and Yangtze plate. Therefore, the deposit should be a typical ultrahigh pressure metamorphic (reformed) eclogite rutile deposit.

After the formation of the deposit, under the influence of geotectonics, metamorphism, fluid, hydrogeology, topography and other factors, the shape and scale of the ore body, surrounding rock and ore structure, mineral composition and grade have changed to varying degrees, and even the deposit has disappeared.

A comprehensive study of the change and preservation process after the formation of the deposit can systematically understand the whole process of the formation and evolution history of the deposit, so as to improve and improve the theoretical content of rutile mineralization, provide information for the evolution of the geological environment of the deposit and provide a basis for rational arrangement of deposit exploration. According to the genesis of the eclogite-type rutile deposit in this area and its changes after its formation, it is preliminarily considered that the evolution of the deposit from its formation to today has mainly gone through the following five stages: (1) pre-eclogite stage, at which time eclogite has not yet formed, and Ti in the rock mainly exists in ilmenite, sphene, white titanium ore and other minerals, and rutile is small in quantity, mainly fine particles, and often transformed into garnet and green titanium ore. (2) In the eclogite stage, when metamorphism reaches its peak, the basic rocks are metamorphic under ultra-high pressure to form eclogite, and the beneficial component TiO2 _ 2 in the original rocks is separated from ilmenite, sphene, anatase and other minerals to form rutile, which is embedded in garnet, omphacite and other minerals formed by simultaneous metamorphism in granular and columnar forms. This stage is the main metallogenic stage of rutile; (3) In the post-eclogite stage, eclogite undergoes deformation and retrogression after its formation, and rutile is replaced by ilmenite, sphene, albite and other minerals, or forms alteration residues; (4) In the hydrothermal filling stage, in the later stage of metamorphism, metamorphic hydrothermal solution (and possibly other types of hydrothermal solution) extracts beneficial components from surrounding rocks, and migrates to joints and fissures formed by deformation under appropriate temperature and pressure conditions, forming pegmatite veins rich in rutile; (5) The deposit preservation stage, in which the deposit is only slightly modified, such as weathering, denudation, leaching, etc. The overall ore quality and mineral resources are basically unchanged.

3.2. 1.2 Update of prospecting marks

According to the ore-bearing characteristics of eclogite in northern Jiangsu and the experience of mineral work, the following combination of prospecting criteria is put forward: (1) concentrated distribution area of eclogite (prospecting prospect) →(2) large eclogite (ore-bearing geological body) →(3) massive eclogite belt (mineralization belt) in eclogite →(4).

Because of the extensive coverage of Quaternary in this area, finding and discovering eclogite has become the primary task of prospecting. Therefore, according to the distribution law of eclogite in northern Jiangsu, the following criteria for searching eclogite are put forward:

(1) Landform symbol: eclogite has strong weathering resistance, and the landform is often in normal terrain such as ridges and hills;

(2) Quaternary sign: Quaternary deposits in the upper part of eclogite are characterized by small thickness, brownish yellow, garnet, rutile and other mineral particles.

(3) Structural signs: Because eclogite is distributed in component zones and closely related to ductile shear zone, if eclogite has been found in ductile shear zone, more eclogite may be found along the distribution direction of ductile shear zone;

(4) Marks of surrounding rock: eclogite and amphibole often appear together in this area, and attention should be paid to whether eclogite bodies are distributed near the latter distribution;

(5) Heavy sand anomaly and placer sign: rutile heavy sand anomaly or favorable terrain near rutile placer;

(6) Geochemical anomaly sign: secondary halo of titanium is often formed in the distribution area of eclogite group, so the soil geochemical anomaly of titanium is indicative;

(7) Geophysical indicators: According to gravity data, eclogite bodies (belts) are mostly hidden gravity high reflections shown by isolated positive anomalies or abnormal isoline twisted belts on gentle background fields, and most of them are not accompanied by negative fields. The magnetic field is characterized by a locally elevated magnetic anomaly in a low negative calm background field, accompanied by many related negative magnetic fields. These local gravity and magnetic anomalies are small in scale, low in intensity, scattered or isolated in spatial distribution, and generally show banding and clustering.

3.2.2 Innovation of exploration methods

3.2.2. 1 macro observation experience

(1) overburden observation. The project innovatively uses overburden as exploration index. According to the characteristics of Quaternary sedimentary thickness, brownish yellow color, garnet, rutile and other mineral particles in the upper part of eclogite, the existence of eclogite can be judged and the prospecting target area can be basically determined.

(2) Observe the rocks. According to the structure, color and composition of eclogite, the approximate rutile content of eclogite can be directly judged by naked eyes, thus providing a basis for further work arrangement and shortening the work cycle.

3.2.2.2 high-precision magnetic survey

The Quaternary system of ultra-high pressure metamorphic belt in northern Jiangsu covers a wide range, so it is very difficult to find and discover eclogite, so geophysical methods must be fully used. The test results of the physical properties of geological bodies in the area show that eclogites, especially massive eclogites, have strong magnetism, high magnetic induction intensity and remanence, and large changes in magnetization deflection angle and dip angle, which are obviously different from those of surrounding rocks and are easy to form regular local magnetic anomalies. Therefore, high-precision magnetic profile measurement is selected as the main geophysical method to carry out the method test. The test results show that high-precision magnetic survey is effective for finding hidden eclogite bodies containing rutile ore. Taking the test of Jiao Xiao mining area in xinyi city as an example, the data obtained by conventional exploration methods (trough, well and drilling) show that the western end of ore-bearing eclogite is clamped on line 09, but the results of this high-precision magnetic survey show that the magnetic anomaly caused by ore-bearing eclogite has not been trapped near line 1 1, and its scale and intensity tend to expand westward. Therefore, high-precision magnetic survey provides an effective technical method and scientific basis for the discovery and evaluation of primary rutile ore.

3.2.2.3 hand twist drill

In many areas of ultra-high pressure metamorphic belt in northern Jiangsu, the Quaternary overburden is thick (3.5~5.0m), the soil is loose and easy to collapse, the groundwater level is shallow (1.0~2.0m ~ 2.0m), and the construction of ground trenches and shallow wells is very difficult. In order to collect surface samples and delineate rocks (ores), the construction test of manual twist drill was carried out. The results show that the twist drill can pass through the common iron-manganese nodule layer, gravel layer and calcareous nodule layer in Quaternary in this area, and penetrate into the weathered bedrock for 0.2 ~ 0.3 m, and can be successfully taken to the ground for observation and sampling. Through experiments, it is considered that hand-cranked twist drills can be used not only to track eclogite, but also to construct twist drills according to a certain grid in mining areas, and to preliminarily delineate the surface scale of rock (ore) and understand its ore-bearing property. Fifty-three hand-operated twist drills were constructed on lines * * * 15, 17, 19, 2 1 02 in xinyi city Jiao Xiao mining area, of which 49 were drilled effectively (able to drill into bedrock surface), with an effective rate of 92.5%, which successfully guided/kloc-0.

This experiment provides an effective working method for solid mineral exploration in shallow overburden area with thick overburden, difficult trench exploration and shallow wells in Quaternary.

3.2.3 Innovation of exploration effect

With the implementation of this project, a large-scale high-grade eclogite-type rutile deposit has been newly discovered, which is an important breakthrough in finding large-scale rich primary rutile deposits in ultra-high pressure metamorphic belt in China. The highest grade of known rutile deposits in China has been improved, and nearly large rutile-rich ore bodies have been obtained, which provides new clues for finding rutile-rich ore bodies.

Exploration and study of large-scale high-grade rutile ore in ultra-high pressure metamorphic belt in northern Jiangxi

Wang Hui, Huang Jianping.

(Jiangsu Geological Survey Institute, Nanjing 2 100 18)

Abstract: There are many eclogite ore bodies, which have good conditions for forming rutile ore. In the process of comprehensive investigation of land and resources, the project has mastered some statistical contents, reached the conclusion that the resources in this area have great potential, and made further long-term plans. On this basis, a large ore body with a grade of 3. 5% was found. 94 percent. The project has also made a major breakthrough in the prospecting theory such as the formation and evolution process and marks of ore bodies, and adopted high-precision magnetic survey and manual twist drill in the exploration of solid minerals in shallow staggered areas, providing new technologies or methods for related fields.

Key words: rutile ore; Large scale; High-grade; Patrol; Prospecting theory; Means of prospecting; Northern Jiangsu Province