Non-ferrous metals are non-renewable resources, so it is necessary to use advanced technical methods in exploration and mining, take effective measures, adhere to scientific and reasonable principles, effectively improve the opening rate of minerals, and fundamentally adapt to the needs of economic and social development.
At this stage, the search for new deposits has become an important task, on the one hand, because of the limited number of easily identifiable deposits on the exposed surface and in the shallow part of the earth, and the difficulty of investigating deposits in the deep part of the earth; secondly, the lack of advanced mineralization model theory, mineralization prediction theory and effective mineral search methods for guidance.
The metallogenic model reflects the understanding of the law of mineral deposits and is a simple overview of the geological, tectonic, geochemical, geophysical and other basic characteristics of the same type of deposits. Mineralization prediction, on the other hand, is the process of quantitative evaluation of mineral deposits with the mineralization model as a premise. It further speculates on new mineral pathways by taking into account the geological environment of mineralization, mineralization conditions, mineralization theory, mineralization signatures and the influence of mineral control factors on potential deposits.
Therefore, we can use advanced scientific methods and geophysical theories as the basis to establish the corresponding metallogenic model guidance in the actual mineral search work, which can fundamentally alleviate the blindness of mineral search work and effectively improve the efficiency of mineral search. It has been proved that the research and prediction of mineralization model can not only make the research of mineralization theory, deposit genesis and the classification law of deposits more systematic and theoretical, but also promote the search for hidden mineral resources in the deep part of the earth to a certain extent.
Since the geological situation of each region is different, the author here mainly takes the non-ferrous metal ore in a certain region as an example, and discusses the metallogenic characteristics and the distribution of ore areas in the region by combining the experience of mineral search in other regions and the characteristics of geological environment.
The concept of nonferrous metals
Non-ferrous metals in a broad sense involves a wide range, which not only includes precious metal minerals such as gold, silver and platinum group, rare earth metal minerals, rare metal minerals and dispersed metal minerals and other metal minerals, but also includes light metal minerals such as aluminum and magnesium, heavy metal minerals such as copper, lead, zinc, nickel, cobalt, tungsten, tin, bismuth, molybdenum, antimony and mercury, etc. It can be said that as long as the ferrous metal minerals are removed, all other mineral resources belong to Non-ferrous metals.
Brief introduction of metallogenic model
Ore-forming model is a high generalization of the ore-forming action in the four-dimensional space, which is finally expressed in different depths, forms and contents, and is gradually deepened with the development of theoretical research on ore deposits. Regional metallogenic model, deposit metallogenic model and ore finding model are three common metallogenic models, which are developed on the basis of the summary of previous research on metallogenic models.
There are certain differences among them but they are distinct from each other. First of all, as far as the regional metallogenic model is concerned, it reflects the metallogenic law of a certain metallogenic area or zone, and is a summary of the characteristics and metallogenic law of various solid minerals in a specific geological unit; the mine field model is not only the expression form of the metallogenic law, but also a model describing the formation process of mineral deposits; while the mineral search model reflects the basic characteristics of minerals and the basic composition of minerals to be
In practice, regional metallogenic model and deposit metallogenic model provide the geological theoretical basis for deposit exploration, while the mineral search model can guide the mineral exploration work, and only the combination of the three can better serve the mineral search work.
Analysis of the geological environment of non-ferrous metal mineralization
The northern part of a region is located in the southeast coastal foreland thrusting and faulting zone of the Eurasian continental plate since the Mesozoic, and has the status of compound superposition with the Yangzi and Huaxia ancient plate combination zone, because the geological environment in which it is located has superiority and special features, thus forming a unique environment for mineralization.
(I) Crust-mantle tectonic characteristics
Since the Mesozoic era, the main geological structure of non-ferrous metal mineralization is crust-mantle structure, through the comprehensive analysis of heavy, magnetic, artificial seismic profile and geodetic electromagnetic sounding and other data, we understand that the crust and mantle of the region has the following characteristics.
(1) The existence of multi-layer detachment zone in the crust.
(2) It is characterized by thin crust and thick upper mantle, with the highest gravity field (+15 mgl) in the area of Boyang, which is the thinnest area of crust in South China.
(3) Its northeastern fracture has significant misconnection to the Moho surface.
(4) The northwestern part is a gravity low anomaly zone, and the gravity high anomaly axis occurs in the north-northeast direction intertwined with the north-east direction.
(5) In general, the thickness of the crust and upper mantle shows a trend of gradual thinning from west to east, and the central part is the axial north-northeast mantle ridge area. The existence of the above features is inseparable from the Mesozoic large-scale rock-forming mineralization.
(2) The paleotectonic pattern before Mesozoic in some areas
After the study of related data, it is found that Huaxia and Yangzi are the paleotectonic patterns before Mesozoic in some areas. Serpentine greenstone has been found not only in Fuchuan, Shexian County, Anhui Province, but also in Dexing and Yujiang, in Liuyang, Hunan Province, and Longyou, Zhejiang Province, where mixed serpentine green tectonics or serpentine greenstone fragments have been found.
(C) Geological and tectonic features of the Mesozoic
In the Mesozoic, there are strong deep and large fracture zone activities, widely developed two major pushover tectonic systems, significant large-scale slip shear and extension, so it has caused many twisted zones and great fracture layers. Especially, the north-east-north-north-east direction, and the east-west and north-west direction of the three major composite terrain is formed due to the frequent occurrence of fracture mountain building and plate fracture movement.
Nonferrous metal mineralization characteristics
Taking the metallogenic characteristics of non-ferrous metals in the northern part of a region as an example, the deposits show different characteristics in terms of metallogenic time, deposit distribution and deposit formation, etc. The best description of the metallogenic time of non-ferrous metal deposits is “multi-phase mineralization and the strongest Yanshan phase”.
In terms of distribution, non-ferrous metal deposits mostly show “block” and “belt” mineralization zoning with deep fracture zone clustering at the edge of the block and “oceanic” zoning along the foreland thrusting and faulting zone; in terms of formation, non-ferrous metal deposits show “block” and “belt” mineralization. The formation of non-ferrous metal deposits is characterized by “multiple mineralization superposition and multi-type aggregation”, and the complex rock control and mineralization control by slip-torsion and push-slip overburden tectonics, which are carried out in a multi-layered manner in both plutonization and in-situ mineralization and mineralization, and the coupling relationship between the controlling factors and distribution environment in large mineralization areas.
The Middle Neogene, Hesperian, Indo-Chinese and Yanshan large-scale mineralization periods are the main mineralization periods, all of which have different characteristics. In terms of the Miocene metallogenic period, it has a certain amount of ancient volcanic rocks, which not only exist in the form of combined late Miocene and Qingbaikou Period volcanic ditch arc-type rocks, but also have a close relationship with copper and gold ore; in the Haixi metallogenic period, there is a part of local mineralization of non-ferrous metals, and even the formed ore layer has industrial significance.
The typical metallogenic feature of the Indo-Chinese metallogenic period is metamorphic hydrothermal mineralization, which includes magmatic hydrothermal related gold and tin ores as well as metamorphic hydrothermal mineralization, mainly formed by gravity; Yanshan metallogenic period, the time of mineralization is about 180-100 Ma between the late Jurassic and early Cretaceous period, influenced by several volcanic movements and magma intrusion position formed large-scale non-ferrous metal deposits.
Prospects for non-ferrous metals
The remarkable mineralization effect in the northern part of the region is mainly due to its frequent volcanic activity, which, together with the Mesozoic and Cenozoic orogenic movements, accelerated the frequency of tectonic magma superposition. In-depth exploration of the formation conditions of gold, copper and other non-ferrous metals reveals that they mainly benefit from the frequent activities of magma, which provides mineral and heat source water for the formation of these non-ferrous metals.
Then by analogy, we can roughly predict the distribution and mineralization types of non-ferrous minerals in the control mineral belt: ductile shear zone type gold, tectonic alteration rock type gold, porphyry and xenolith type copper-gold ore and marine jet sedimentary stratified control type copper ore, all of these mineral resources show a better development prospect. Therefore, in order to fundamentally alleviate the shortage of non-ferrous metal mineral resources, it is necessary to accelerate the exploration of the peripheral geology and the deep part of large mineral production areas.