The southwest Hubei-Southeast Sichuan-Qianzhongnan Zhuangping layer hydrothermal barite ore cluster is located in the upper Yangtze platform fold belt, and its geographical location includes southwest Hubei, southeast Sichuan, northeast Guizhou, and central Guizhou. Spread.

1. Regional geological background

The mining area is located in the Yangtze platform fold belt (E-Qiantai fold belt) on the secondary tectonic unit in the Yangtze plate. The marine caprocks from Paleozoic to Middle Triassic developed well. The Indosinian movement all rose to land, and the Yanshan movement all folds, forming a platform cover fold belt. However, Jurassic folds are the main form of caprock deformation in this area. They are widely developed in western Hubei, western Hunan, eastern Sichuan, and eastern Guizhou, and are composed of Lower Paleozoic, Upper Paleozoic, Triassic, and Jurassic. The folds are a series of equally spaced anticlines and synclines, and are controlled by two sets of north-north-east and north-east-east (near-west) fold basement fracture grids, showing a gently north-easterly arc spread. Or a multi-letter arrangement. In the Mesozoic (Indosinian-Yanshan Movement), the above-mentioned caprock tectonic folds formed during the collision from the Middle Triassic and continued to the Middle Cretaceous.

The barite deposit in this area is obviously controlled by the above-mentioned tectonic fold fault zone. Take southeastern Sichuan as an example: the folds and fault groups in this area are distributed along the north-north-east direction, and the folds are dozens to hundreds of kilometers in length. During this period, each anticline controls one subore zone, a total of six subore zones. There are more than 300 barite veins; there are also fluorite-barite ore belts, mercury ore belts, and lead-zinc mineralization belts controlled by anticlines in northeast Guizhou.

2. Metallogenic characteristics

Strata-type barite ore is one of the main types in the ore cluster area, and the metallogenic area is relatively large. It is an important source of this type of deposit in China. It is mainly distributed in western Hubei, southeast Sichuan, and western Guizhou. The ages of the surrounding rocks of the deposit are Late Cambrian, Early Ordovician, and Early Permian and Early Triassic in central and western Guizhou. The barite deposit was formed in the Yanshanian period. It is mainly present in the Upper Cambrian-Lower Ordovician carbonate rocks, and there is no magmatic rock distribution in a wide area, indicating that the mineralization of fluorite and barite has no obvious relationship with magmatic activities. Hundreds of barite deposits (points) have been found in the area, mainly small and medium. The output and distribution of the ore deposit or ore body are strictly controlled by the north-northwest-to-northwest extensional and extensional torsional fault groups, with steeply inclined vein-like and lenticular production.

3.Typical deposit

Guizhou Shibing County Dingtanpo Barite Deposit, the barite manufacturer's deposit is located 2km south of Shi Bingcheng.

(1) Regional geological background: The ore deposit is located in the middle of the Yangtze platform fold belt on the Yangtze quasi-platform, near the east-west Guiyang-Qujiang fault through the mining area.

(2) Metallogenic environment: The barite deposits occur in the Upper Cambrian-Lower Ordovician, and in the upper Cambrian-Lower counties of Huangping, Kaili, Majiang, Guiding, and Duyun counties outside the mining area. Ordovician, all have barite mine output. From top to bottom, the ore-bearing stratum is the Lower Ordovician Dawan Formation. The upper part is gray-green thin sandy shale intercalated with limestone, and the lower part is limestone, argillaceous limestone, and calcareous shale. ②Red Huayuan Formation: light gray middle-layer limestone and bioclastic limestone; ③ Tongzi Formation: fine-grained dolomite and lime-like dolomite in the upper part, argillaceous limestone and calcareous shale in the middle, and middle-layer limestone and dolomite in the lower part Limestone. The Upper Cambrian Lushan Formation is light gray-off-white medium-fine-grained dolomite.

(3) Orebody distribution and occurrence: The barite ore-bearing zone is 900m long and has 17 barite veins. It is distributed side by side. It is a steeply inclined orebody that stretches along the northeast to southwest and stretches and twists. Sexual fracture filling. Generally inclined south-east, the inclination angle is 55 ~ 70 °. The length of a single vein ranges from 30 to 80 m, the horizontal thickness is 0.2 to 20 m, and the extension can reach 70 m. Surrounding rock alteration is weak and small in scope, mainly including weak silicification, calcite, and dolomite.

(4) Ore type and mineral combination: It is a single barite deposit. There are three types of ore: block, plate and honeycomb.

(5) Ore structure: columnar structure; block, plate and honeycomb structure.

(6) The content of useful components: The lump ore contains about 495% BaSO, the plate crystal ore has a BaSO4 content of 98%, and the honeycomb ore has a BaSO4 content of about 90%. Contains strontium from 0.96% to 1.64%.

 (7) Physical and chemical conditions of mineralization: The mineralization temperature of this deposit is 130 ～ 220 ℃, which is as high as 276 ℃. The sulfur isotope composition δ34S value is + 28.82 × 10-3 ～ + 16.13 × 10-3, which belongs to heavy sulfur.

4. Ore-forming law

 The Sinian-Lower Cambrian is a barium source layer, and the Cambrian-Ordovician evaporites are sulfur source layers, which are collectively called ore source layers.

The carbonate and argillaceous and argillaceous rocks of the Upper Cambrian-Lower Ordovician are ore-bearing layers and shielding layers, respectively. Oil and gas generation, storage, and capping combined systems that make up a barite deposit.

The ore-forming medium is chloride brine formed by dissolving and evaporating salt rock in atmospheric precipitation. A2 + is extracted from the chloride brine and transported to a shallow SO42-rich environment for precipitation as a barite deposit.

The Wuling caprock structure controls the F-Ba series of fluorite-barite ore belts (top), and the Hg-Pb-Zn-Cu-Ba-F series of mercury ore belts or lead-zinc ore belts (bottom). Vertical sequence.

5. Mineralization mode

The barite, fluorite, lead-zinc, and mercury ore belts in the ore cluster area have similar material sources, forming a ore belt sequence that forms a very clear reducing and oxidizing environment in the vertical direction. Based on the typical ore-forming pattern of the layered deposits, the barite deposits are briefly described as follows:

 (1) Atmospheric precipitation infiltrates into the ground and is heated with increasing depth, directly dissolving the paste salt into hot brine, or mixed with deep formation brine.

(2) The brine is restricted by the rule of vertical zoning of water chemistry. Most of the SO42-type water is concentrated in the shallow layer, while the chloride brine is mainly concentrated in the bottom layer, so the SO42- and Cl- in the brine generated by dissolving the paste salt are separated . SO42- migrated to the shallow layer, and the brine containing C1 concentrated to the bottom layer.

(3) Chloride brine leaches elemental components such as Ba in the underlying Ba source layer to form ore-containing brine, which is mainly present in the brine as BaCl2.

(4) Due to the effects of heat release due to geothermal gradients, tectonic movements, etc., the Ba-containing brine is warmed and driven. It rises along the fracture migration to the shallow layer and meets SO42-type water, prompting rapid changes in physical and chemical conditions ( The pressure decreases, Eh increases, and the pH decreases), so Ba2 + and SO42--synthesized barite precipitate in the fracture space.

Due to the shielding effect of the overlying argillaceous rock layer, the above-mentioned ore-forming process can be repeatedly and slowly performed until the Guizhou barite deposit is completely formed.