Red antimony ore; Placer gold mine; Output characteristics; Cause analysis; Metallogenic model; Yinding Sb-Au deposit
The Yinding Antimony Gold Mine in Tiane County, Guangxi Province is the exploration work entrusted by Tiane Hong Xin Mining Co., Ltd. to Hechi Geological Survey and Design Institute on 20 1 1, and a phased summary report was submitted.
According to the exploration data, this paper thinks that the red antimony ore and placer gold ore in this area have certain research value. By analyzing the evolution of primary antimony gold deposits (bodies) in the surface environment, the migration and re-enrichment of antimony and gold elements, a metallogenic model is put forward, which is of guiding significance for finding the same type of antimony placer gold deposits. This article is specially written to discuss with * * *.
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The Yinding Sb-Au deposit in Tian 'e County, Guangxi is located in the southwest margin of Yangtze paraplatform and South China fold system, and at the north inclined end of Tian 'e anticline (see right: regional geological map). Dulong-Yinding area is located in the core of anticline, and the exposed stratum is Lower Carboniferous Datang Stage (C 1d). The core is densely banded with folds, structures and joints, and is often filled with calcite veins.
The exposed strata in this area are mainly Triassic, Permian and Carboniferous. Triassic is a set of variegated sand shale, conglomerate, pyroclastic rock and tuff; Unconformity on Permian limestone. Permian and Carboniferous are a set of medium-thick layered limestone with a small amount of bioclastic limestone. No igneous rocks have been found in this area.
2. The main characteristics of the deposit
2. 1 Landform characteristics of the mining area
The mining area belongs to the limestone denudation area of Yunnan-Guizhou Plateau, with an altitude of 630- 1 100 m, which is a typical karst landform. Karst is extremely developed in this area, including multistage karst and oval, long and irregular karst depressions, funnels, valleys and caves with diameters ranging from tens of meters to hundreds of meters. The valleys and depressions are mostly dry and waterless, and red antimony ore and placer gold ore are distributed in karst landforms formed by limestone.
2.2 Occurrence state and characteristics of red antimony ore and placer gold ore
(1) Red antimony ore and placer gold ore are distributed in disorder in the Quaternary surface soil layer and sandy clay layer below it, sometimes the largest one is above it and the smallest one is below it, and they are arranged in disorder. Placer gold deposits are generally mixed under red antimony deposits.
② A small amount of manganese nodules and limonite nodules coexist with the seam. At the bottom, calcite, timing, limestone, sandstone and shale can be seen occasionally.
(3) Red antimony ore and placer gold ore are often found in the fissures of yellow clay accumulated by weathering and dissolution in fault fissure zones (see photo 2).
2.3 Ore Composition and Structure
The material composition of placer gold ore is simple, mainly natural gold, golden yellow, with a particle size of 0.0 1-5 mm, which is flaky, scaly, irregular granular and bean-shaped. It is often distributed at the edge of calcite vein with granular fine calcite, kaolinite, Yingshi and fluorite, and the purity of natural gold is relatively high, generally above 900‰. Gold particles are generally dispersed in the form of stars, and sometimes they are enriched in the form of bags or nests.
Antimony has a complex chemical composition, which is a mixed crystal of antimony trioxide and antimony trioxide, and its composition is 2Sb2S3. Sb2O3, when stibnite is in semi-oxidized state, is an unstable mineral. There are still high contents of CaO, SiO2 _ 2, Fe _ 2O _ 3, Al _ 2O _ 3 and other substances in mechanically mixed-crystal ores. Red antimony ore is opal-shaped (see photo 1), including spherical, ovoid, granular, dark and massive. Those spherical, oval, granular and a few dull ones have very smooth surfaces. Block, relatively complete edges and corners, and the surface is not smooth; Most of a single antimony ore is as big as a bean, and a few of them weigh tens of kilograms. Red antimony ore generally contains 42-65% antimony.
2.4 Wall Rock Alteration and Ore-controlling Structure
From the calcite vein of primary antimony gold (antimony gold sulfide) (see photos 2 and 3), the wall rock alteration is extremely weak, and only a small amount of kaolinite, fluorite and dissolved granular quartz are found at the contact edge between calcite vein and wall rock and near the ore-rich bag.
The calcite vein of primary antimony gold (antimony gold sulfide) is obviously controlled by NE-trending faults and Ancient Karst Cave formed along faults and fractures. The occurrence of veins is consistent with that of structural fractures, and ore-rich packets often appear at the intersection of main faults and their adjacent pinnate fractures.
3. Discussion on metallogenic model
Trace element analysis of gold and antimony in this area shows that the abundance of gold and antimony in lower Triassic clastic rocks, pyroclastic rocks and tuffs is much higher than that in similar rocks in other areas, while the abundance of gold and antimony in Carboniferous and Permian limestone is almost the same as that in carbonate rocks.
During the weathering process of gold-antimony deposits in Triassic and high gold-bearing antimony clastic rock series, gold-antimony particles migrated to the underlying caves and fractures with the leaching of corresponding debris, and under the action of seepage hot brine, primary antimony-gold (antimony-gold sulfide) calcite veins were formed, which were strongly oxidized and dissolved under hot and humid climate conditions, forming placer gold and red antimony ore.
To sum up, the author thinks that the metallogenic model of this deposit has the following six steps:
In the first step, the Wu Dong movement caused a large number of cracks, fissures and joints in Carboniferous and Permian limestone, and karst caves were formed along the fissures under the action of groundwater.
The second step is Indosinian movement, where Triassic clastic rocks with high abundance of gold and antimony were deposited.
Thirdly, weathering and leaching of Triassic clastic rocks make some gold and antimony particles and timely debris or colloid migrate to Carboniferous and Permian limestone caves and fractures at the bottom of Triassic or below.
The fourth step, under the action of seepage hot brine, the gold and antimony particles at the bottom of Triassic system are further activated and filled in caves and fractures together with hot brine. Under the change of physical and chemical conditions of the medium, gold and antimony particles precipitate on the edge of calcite vein.
Fifth, under the strengthening effect of hot brine with high salinity, timely debris, gold, antimony particles and argillaceous materials in caves and fractures are kaolinized, and timely particles are recrystallized and partially dissolved, so that gold and antimony are relatively enriched and gold particles proliferate, forming primary antimony gold (antimony gold sulfide) calcite veins.
Step 6, after the calcite vein of primary antimony gold (antimony gold sulfide) is strongly oxidized and dissolved under the hot and humid climate conditions, gold is enriched in the low-lying cave in the form of simple substance (placer gold), and antimony reacts with negatively charged colloidal solution in the form of anions to precipitate and condense to generate red antimony ore. Due to the further development of karst, the denudation and undercut of topography, and the collapse of underground rivers and caves caused by gravity or large-scale collapse, red antimony ore and placer gold ore are dispersed in the quaternary topsoil and sandy clay layer of the above topography by short-distance transportation.
4. Conclusion
Yinding Sb-Au deposit in Tiane County, Guangxi is a special type of red antimony deposit and placer gold deposit. Studying its ore-controlling conditions and metallogenic model has certain theoretical and guiding significance for the prospecting of red antimony and placer gold in carbonate karst depression.
refer to
[1] Guangxi Regional Geological Survey Team, 1969, Regional Geological Map (Nandan Sheet1/200,000).
[2] Wang Chunsheng. Genesis and prospecting significance of Jiaoman calcite vein type gold deposit.
[3] Huang Renjun. 1994, "Occurrence Characteristics and Genesis Analysis of Red Antimony Ore in Youjiang Valley, Guangxi"
Brief introduction of the author
1, Wei, male, geological engineer, national registered safety engineer, engaged in mineral geological exploration and hydraulic environmental geological investigation for a long time.
2. Yang Li, male, geological engineer, has been engaged in mineral geological exploration and hydraulic environmental geological investigation for a long time.