Tongling ore concentration area is located in the middle of Guichi-Maanshan (Indosinian) uplift belt in the southeast of the lower Yangtze Indosinian uplift belt between the Yangtze block and the North China block, which is a relatively independent rhombic block. The metallogenic belt belongs to Anqing-Tongling-Fanchang copper-iron-lead-zinc-gold-silver-pyrite-alunite metallogenic sub-belt.
1. Brief description of mine geology
(1) stratum
The exposed strata in the mining area are Silurian, Devonian, Carboniferous, Permian, Triassic and Quaternary. Triassic is exposed in the middle of the mining area, and consists of Yinkeng Formation, Helongshan Formation and Nanlinghu Formation of Lower Triassic, Dongma 'anshan Formation and Yueshan Formation of Middle Triassic. Among them, Helongshan Formation and Nanlinghu Formation are the main ore-bearing strata. Helongshan Formation is mainly composed of limestone, argillaceous rock and calcareous shale, while Nanlinghu Formation is mainly composed of limestone, breccia limestone, bioclastic limestone, dolomite limestone and calcareous shale.
(2) Structure
The structure of the mining area is complex, and the Indosinian-Yanshan period experienced multi-stage structural deformation, which consists of three groups of main faults: NE, NW and NNE, among which the NW-trending fault structure plays an important role in controlling the local enrichment of the deposit. The intersection of Xinwuli syncline and nearly east-west basement fault controls the emplacement of Xinwuli rock mass and the formation of ore field.
(3) Magmatic rocks
The Yanshanian magmatism in this area is intense, and the intrusive rocks are mostly rock plants and rock-like hypabyssal intrusions. Xinwuli rock mass is a compound rock mass formed by multiple surges and intrusions of granitic magma. Controlled by the NE-trending fold structure and its associated NE-trending, NE-trending, NW-trending and NW-trending fault structures, the exposed area is nearly 10 km2, which is the largest rock mass in Tongling ore concentration area. Its main lithology is timely diorite (rock edge) and granodiorite (middle part of rock mass).
2. A brief description of the characteristics of the deposit
(1) ore body characteristics
There are mainly four ore bodies in the mining area, among which the No.2 ore body is the largest, all of which occur in the contact zone between intrusive rocks and surrounding rocks and its vicinity. Among them, 1, No.2 and No.3 ore bodies occur in the contact zone between Fenghuangshan rock mass and Nanlinghu limestone, and No.4 ore body occurs in the contact zone between rock mass and Longshan limestone and is controlled by the contact zone. The main ore bodies are generally 300 ~ 10~80m long, 0 ~ 80m thick and 200 ~ 600m inclined. Ore bodies are closely related to skarn and controlled by faults and contact zones. The ore bodies are mainly plate-shaped and irregular lenticular. The nearly north-south expansion structure has the characteristics of multi-stage activity, forming breccia ore. Secondary ore bodies and small ore bodies are mostly distributed in marble, skarn and intrusive rocks near the main ore body.
(2) Ore type and structure
According to industrial types, the ores of Fenghuangshan copper deposit can be divided into seven types: massive copper-bearing magnetite, hematite, massive copper-bearing siderite, breccia ore, disseminated copper-bearing garnet skarn, massive copper-bearing pyrite, disseminated copper-bearing granodiorite and disseminated copper-bearing marble. Copper-bearing magnetite, hematite and copper-bearing siderite are the main ore types. Different mineralization types have obvious boundaries in space and are consistent with the distribution direction of ore bodies. Copper-bearing magnetite and hematite are mainly distributed in the core of the ore body, and the phenomenon of branching and compounding appears in the No.2 ore body. Copper bearing siderite is distributed around copper bearing magnetite and hematite. Pyrite-type ore is distributed at the edge of 1 ore body and appears at the core of No.2 ore body. Other types of ore mostly occur on both sides of the ore body.
Specimen name copper-bearing magnetite. DB070 Stratigraphic Age Yanshan Period
Atlas of large ore specimens from typical mines in China
The surface of the specimen is brownish red, semi-authigenic granular structure and massive structure. Ore minerals mainly include chalcopyrite, pyrite, magnetite, hematite, bornite and chalcocite. Gangue minerals mainly include quartz, calcite and garnet. The grade of copper is 0.56%
Genesis of skarn type in Fenghuangshan copper mine, Tongling City, Anhui Province