Geological Characteristics and Regional Prospecting Model of Wulanchongji Gold Orebody, Alxa Youqi, Inner Mongolia, China

Five gold deposits (mineralization) were found in the study area by means of geological mapping, soil geochemical survey and trough exploration engineering. The ore-bearing lithology is mainly metamorphic feldspar sandstone of the Upper Carboniferous Benbatu Formation, and the gold (mineralization) body is controlled by both structural factors and stratigraphic factors of the Upper Carboniferous Benbatu Formation. The genetic type is preliminary concluded to be volcanic hydrothermal type, and the metallogenic age is late Variscan. In this paper, by studying the geological characteristics and metallogenic geological conditions of the gold orebody in the area, a regional prospecting model has been established, which is of great significance to better guide the prospecting work of similar gold deposits in the area and the region.


Introduction
The research area is located 220 km northwest of Bayanhot Town, the government seat of Alxa Zuoqi, within the territory of Tamusubraga Town, Alxa Youqi, Inner Mongolia Autonomous Region of China. The study area is located in the Ejinaqi-hinggan mountains proterozoic era, variscan, Yanshanian of Cu, Pb, Zn, Au, Ag, Gr, Nb as a mining area, Wuliji-Xilinhaote proterozoic era, variscan, Yanshanian of Cu, Fe, Gr, Au, Fluorite metallogenic belt [1] [2] [3] [4]. The discovered gold deposits in the vicinity of the study area include Zhulazhaga gold deposit and Chaganchulu gold deposit, which indicate that this area has a good 2. Regional Geological Background Regional inland emerging extensive exposure, there are Carboniferous, Cretaceous, Quaternary strata. The area of magmatic rocks is limited, mainly Permian and Triassic intrusive rocks. The region has experienced multiple periods of tectonic superposition, the main direction of the tectonic line is NEE, followed by NWW and nearly EW, and the late superposition of NE and NW, forming a complex tectonic framework.
Among them, the Upper Carboniferous Benbatu Formation (C 2 bb) [11] is the oldest strata outcropping in the area, and it is also the strata most closely related to gold mineralization. It is mainly distributed in the central and northern part of the area, with a small amount distributed in the central and western parts and southeast parts. The stratigraphic trend is mainly NEE and NWW. The lithology of the formation is mainly metamorphic sandstone, metamorphic feldspar sandstone, metamorphic feldspar quartz sandstone, intercalated tuff, intercalated crystalline limestone and a few phyllite. Due to the influence of regional dynamic metamorphism, the rocks in this formation are mostly slightly metamorphic, and some of them develop in pieces. The strata of this formation were intruded by Early Permian monzonitic granite in the central and western part of the region, and most of them were unconformably covered by the Wulansuhai Formation of the Upper Cretaceous.

Magmatic Rocks
The regional magmatic rocks are mainly intrusive rocks, followed by volcanic rocks.
The upper intrusive rocks are mainly distributed in the western part of the region in the NNE direction, which is consistent with the general tectonic line direction of the region. There are two mapping units, namely, Early Permian Medium-fine grained monzonitic granite (P 1 ηγ) and Early Triassic diorite porphyrite (T 1 δμ). Volcanic rocks in this region are pyroclastic rocks, i.e. tuff in the strata of

Metamorphism
According to the distribution of metamorphic rocks, the regional tectonic environment and the relationship between the metamorphic rocks and fault structures and magmatic intrusions, the metamorphism in the region can be divided into three types: regional metamorphism, contact metamorphism and dynamic metamorphism. Among them, regional metamorphism is dominant, contact metamorphism and dynamic metamorphism are relatively limited.
The Upper Carboniferous Benbatu Formation was transformed by regional metamorphism, by regional low temperature dynamic metamorphism of low green schist facies in the early stage, and superimposed by dynamic metamorphism and local contact metamorphism in the late stage.

Structure
The upper level tectonic unit belongs to the North China Plate, the second level tectonic unit belongs to the North China continental margin proliferation zone, and the third level tectonic unit belongs to the Baoyintu-Xilinhot volcanic passive continental margin [12].

Genetic Types of Ore Deposits
The known gold deposits in Inner Mongolia can be divided into 5 major types and 20 deposit subtypes: heavy lava magma hydrothermal gold deposit, meta-

Regional Prospecting Model
Based on comprehensive analysis of regional metallogenic geological background and metallogenic regularity and comparative analysis of regional important ore sites, it is considered that the metallogenic geological conditions of the gold deposit (mineralization) point in this study area are similar to those of Chagan- Through comparative analysis and combined with the unique metallogenic conditions in this area, the regional volcanic hydrothermal type gold polymetallic ore prospecting model is established (Table 1). Controlled by NEE trending fracture.

Magmatic rocks
The ore-bearing geological bodies occur in the subvolcanic rocks, and the lithology is cataclastic subdacite. The subvolcanic rock mass is situated in the upper Carboniferous Amushan Formation in EW direction.
In the surrounding rock far away from the orebody (the surface is 460 m south of the orebody), there are volcanic clastic rocks of the Benbatu Formation, whose lithology is rhyolitic lithic and dacitic lithic clastic tuff.
Ore source Stratigraphy of Amushan Formation and volcanic hydrothermal fluid.
It is mainly from Benbatu Formation, and partly from volcanic hydrothermal fluid.
Main ore-controlling factors Structural and intrusive subvolcanic rocks (cataclastic subdacite) in the amushan formation.
Structure and stratigraphy of Benbatu Formation.
The mineralization of surrounding rock The surrounding rock of the top and floor of the gold mineralized bed is limestone of Amushan Formation and pebbled calcareous sandstone.
The surrounding rocks are metamorphic feldspar sandstone, crystalline limestone and phyllite of the Bemba Tu Formation, while the surrounding rocks in the distance (the surface is 460 m south of the orebody) are rhyolitic lithic crystal tuff and dacitic lithic crystal tuff.

Conclusion
At present, the work level of Wulan Chongji gold deposit is very low. The regional prospecting model established according to its geological characteristics and metallogenic geological conditions will play a positive guiding role in the prospecting work of this study area and similar gold deposits in the region.