Mineral search mode and direction of mineral search
This paper takes the gold ore in an area as an example, where there are mainly two types of gold ore, namely, fracture zone alteration rock type and shear zone alteration rock type, and the output and distribution of each deposit (point) are subject to certain geological factors and have their own signs of finding ore. Among them, the former is mainly represented by the large plate gold mine, while the latter is mainly represented by the large scale Pai Shan Lou gold mine.
(I) Stratigraphic lithology signatures
The stratigraphic control characteristics are the distinctive features of gold ore in this region. The case rocks and deep-formed intrusive bodies of the Taurian period directly influence the fracture zone alteration type and alteration type gold ore, and their lithology is dominated by hornblende and long-engine chyolite system.
(II) Magmatic rock signatures
The ring structure in remote sensing interpretation is one of the ore finding signs of gold in this area, which is obtained by the geological proof of gravity and aeromagnetic. It is mainly due to the fact that the Mamluksan rock body and some small rock bodies to its north are connected together at its depth, thus leading to the fact that most of the gold ores in this area are above the hidden rock bodies. In addition, the frequent activities of magmatic activities in the area provide water and material sources as well as some heat sources for the formation of metal ores, which to a certain extent has given rise to the formation of metal ores. The affiliation of veins and small rock strains with the main rock body, the possibility of searching for new veins in the contact zone on both sides of medium and acidic intrusions or veins.
(C) Tectonic sign
The tectonic control of gold ore in this area is obvious, from the distribution of mineralization zones to the formation of deposits and ore bodies are controlled by tectonics at all levels. The regional deep major fractures are both ore-conducting structures and control the distribution of ore fields and deposits: the widely developed secondary near-EW and NW fractures control the ore bodies and ore belts. The former is early compressional-torsional and larger in scale, often forming a north-west-trending stacked tile recoil (mask) thrust structure. With the help of its pushing and shearing effect, the area will form a large scale of mylonitization zone and extrusion shear lamellarization zone, and the extensional slip tough-brittle activity of these tectonic weak zones in the late stage makes it become the guide and ore-holding structure of the Pai Shan Lou type and large plate type positive shear zone type gold ore; the latter is mostly tensional-torsional, smaller in scale, and often forms a group of NW directional right rows of geese column fracture zone, which is The main guide and ore-holding structure of alteration rock Ying vein type gold ore.
Stratigraphy and mineralization
The stratigraphy exposed in the area is relatively simple, including: Taiyu metamorphic case rocks, the Great Wall System and the Jixian System in the Middle Paleo Period, the Jurassic and Cretaceous Systems in the Mesozoic Period and the Fourth System in the Cenozoic Period. The former is divided into four group-level lithostratigraphic units, and the latter can be divided into five, which are distributed on or around the metamorphic deep-formed rocks of the Tauric, and are mostly tectonically in the form of tectonic sheets or flysch of different sizes, all of which are a combination of endogenous carbonates and land-derived clastic rocks. The rest are mainly dolomite, dolomitic chert and feldspathic quartz sandstone. Pai Shan Lou and other gold mines in the area, in the gold mineralization process in the region may play a physical and chemical barrier role, so as to promote the mineralization process. This is related to their geographical location, are produced in the middle and upper metasedimentary stratigraphic distribution of the nearby section of the Taurian metamorphic deep shear parts, and by the middle metasedimentary strata constitute the top plate of the deposit.
Magmatic rocks and mineralization
Considering the rock chemistry, mineral combination and paragenetic characteristics of the rocks, it is presumed that the granite in this area is mainly of type I, supplemented by type S. The magmatic rocks in the area are more developed, and the exposed magmatic rocks include granitic rocks of Taiyang Dynasty, Hualixi Stage amphibolite, Yanshan Stage granite and so on. The intrusive rocks have different intensities and scales in different periods, among which the most intense and widely distributed in the Tertiary and Mesozoic periods, while the Mesozoic intrusive rocks are the second in scale and intensity. In addition, the Taiyan and Mesozoic magmatic rocks also influenced the formation of gold ore to some extent.
(I) Tauric metamorphic deep-formed rocks
The Tauric metamorphic rocks in this area are composed of the Baiyuan Gneiss and the Tauric Xiaomaling Gneiss, with a north-northeast trending belt. The former lithology is diagenetic and granulitic gneisses. The latter rocks are mainly composed of quartz amphibolite, orogenic granitic gneisses and inyun amphibolite gneisses, of which inyun amphibolite gneisses are the main constituents. The rocks are all subjected to ductile shearing and most of them are transformed into mylonite-like rocks. In addition, there is also a small amount of Suizhong gneiss, whose main lithology is granitic gneiss.
(B) Middle Age intrusive rocks
The gold ores in this area are distributed in a certain range around the Mesozoic intrusive rocks, and mostly formed in the Mesozoic. The area is composed of two units, both of which are in the northern part of the area, the lithology of the former is gneissic oblique granite, and the latter is gneissic diorite.
(C) Mesozoic intrusive rocks
1、Early Permian small Oley Yingzi super unit: mainly distributed in the northern part of the area, locally exposed, composed of medium-grained potassium long granite. In addition, there are also a small amount of quartz amphibolite outcrops; 2. Late Triassic rocks: a well-developed unit in the area, lithology is mainly amphibolite; 3. Early Jurassic Shaoleng super unit: composed of four units in the area, mostly in the form of rock strains, lithology is mainly diorite and granite amphibolite; 4. Middle Jurassic Haitang Mountain super unit: mainly in the northern part of the Pai Shan Lou gold mine, composed of two units, lithology 5、Late Jurassic Lushan superunit: mainly composed of three units, with granite, granodiorite and diorite as the main lithologies.
Geological structure and mineralization structure
The geotectonic position of this area is Yanshan platform fold belt – Liaoxi platform trap – Beizhen bulge, which belongs to the tectonic domain of the coastal Pacific Ocean. Therefore, the basic outline of the regional tectonics is a basin-ridge tectonic combination consisting of a Mesozoic volcanic rock fault basin and a tectonic miscellaneous rock uplift belt spreading in a north-northeast direction. Specifically, the inner edge of the west side of the uplift zone is the Jinzhou-Harr set of ductile fracture zone, the east edge of the uplift zone is the west edge of the Tanlu Fault influence zone, and the west side of the Beizhen Bulge is the Jinzhou-Harr set of fractures. Among them, the main controlling factor of gold ore in this area is the uplift area and the Mesozoic brittle and ductile fracture structures developed in it.
(I) Brittle fracture structure
The NE-NNE fractures are mainly located between the Beizhen Bulge and the eastern edge of the Fuyi Basin, forming an NNE-oriented fracture zone about 10 km wide and 180 km long, which is regionally known as the Jinzhou-Hal Crustal Fault. It is characterized by multi-phase activity, mainly compressional-torsional, followed by tensional-torsional. The fracture surface is mostly NW-dipping with an inclination of 60°～80°, in which extrusion lamellae, fault mud and tectonic lenses can be seen. The fracture has a direct influence on the occurrence, development, evolution and volcanic eruption and deposition of Yanshan-age fracture basins. Secondly, the near-EW-oriented fractures are mostly sporadically distributed in the terrigenous bodies of the Tauric, often cut by NNE and NW-oriented fractures, which are small in scale and compressive.
(ii) Ductile shear zone
The north-northeast ductile shear zone in this area is large in scale, mainly composed of mylonite and various types of tectonic schist, distributed in the NNE direction, tilted north-west, dip angle of 30 ° ~ 70 °, about 150 km long and more than 10 km wide. The rocks are strongly lamellarized, with quartz elongated, feldspar in a residual patchy and eyeball-like pattern, and dark minerals arranged in an obvious direction. The rocks are spatially zoned with obvious intensity, from the edge of the deformation zone to the center in the order of fractured rock zone, coarse vuggy rock zone and vuggy rock zone.
In summary, when conducting research on the direction of metal ore search and geological characteristics of deposits, for metal ores with good mineral quality conditions, we should take into account the conditions of ore-control structures, the presence of ore-forming strata, and the distribution of ore-forming-related information, and make full use of known ore-forming laws for mineral prediction on this basis. In addition, for geological prospecting work, its successful implementation is inseparable from advanced scientific research and survey technology on the one hand, and secondly, it is necessary to ensure that geochemical methods, geology and geophysics are in the best combination.